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WOTs COOLANT LEVEL SENSOR / SERVICE HIGH VOLTAGE CHARGING SYSTEM MESSAGE DEFEAT PLUG

337K views 684 replies 166 participants last post by  onewheeltom 
#1 · (Edited by Moderator)
MOD EDIT: WopOnTour is currently on an extended absence and we're not sure when he's returning or shipping more of these devoces. Until he returns, we would recommend you try a similar device being offered by others further down in this thread, such as this one.

OK folks, WOT's Replacement Coolant Level Sensor (SHVCS Defeat Plug) is ready for deployment!

I helped someone I know very well to create a low cost replacement level sensor that plugs into the connector harness the factory coolant level sensor.
Once completed, (following the special instructions) it "mimics" a properly operating sensor at the correct coolant level, PERMANENTLY mitigating the possibility of ever getting the dreaded SERVICE HIGH VOLTAGE CHARGING SYSTEM (SHVCS) message.

Unfortunately, it's likely not a matter of IF but WHEN as these level sensors have been failing left and right (IMO due to a combination of temperature and vibration) and currently there's no plans to redesign the sensor. (apparently content on letting the dealers replace the sensors in some cases almost bi-annually! lol) LOTS of documented cases in our main SHVCS thread here: http://gm-volt.com/forum/showthread.php?13194-quot-Service-High-Voltage-Charging-System-quot-Message

The only real caveat in using the WOT's Coolant Level Sensor (SHVCS Defeat Plug) is that the owner must visually check their battery coolant level at least monthly (as outlined in the owner's manual) just as car owners have been doing for over 100 years! lol

Additionally, there's no real concern that using this device could result in a battery overheat issue as those are completely different DTCs (based on the battery temp sensors) and all have fail-safe behavior that utilizes "reduced propulsion power" to protect the battery even if there's zero coolant.
(keep in mind on many EVs, such as the Nissan Leaf, coolant isn't even used to cool the battery)
This device will not affect your warranty as it is an "aftermarket replacement part" as stipulated under the Magnuson Moss Act.

So far, a few dozen of these have been constructed (version 1) and will ship with complete instructions (that I had a hand in) that must be followed to the letter in order to prevent triggering the P1FFx series of DTCs while installing the device.(basically the car must be "asleep" when the device is installed as the system monitors the coolant level even when OFF or when charging)

IMPORTANT NOTE: This device needs to be installed BEFORE the "Service High Voltage Charging System" appears as once triggered there is NO CHOICE but to visit a dealer and let them try to figure out what’s wrong (bad level sensor usually) THEN eventually figuring out the only way to CLEAR the combination of DTCs P1FFF and P0AA6 is to “Reprogram the HPCM2” (they will say “a software update was needed” but…) Unfortunately the coolant level sensor is not listed as a Voltec or emissions warranty part, so typically unless you are under the original "bumper to bumper" warranty they will try to ding you anywhere from $100-500 for these repairs!

So to be effective at preventing this annoying and costly repair (some people have had the sensor replaced 3 times!) WOTs Coolant Level Sensor (SHVCS Defeat Plug) must be installed pre-emptively on a properly operating car.

Currently it will work on ALL Gen1 Volts, Amperas, and ELRs.
*NOTE*The Gen2 Volt is a bit different as the sensor is now part of the reservoir (potentially making the repair even MORE expensive) However we have yet to experience anyone with a Gen2 getting the SHVCS message yet, so perhaps the Gen2 will never have the issues the Gen1 cars are plagued with.

We have been testing this solution now over the past couple years and have 12 cars (including one Volt of each model year plus a MY14 ELR) operating with various prototypes of this device for the past 12-months with no ill effects. MISSION ACCOMPLISHED!

EFFECTIVE IMMEDIATELY DUE TO AN INCREASE IN MATERIALS AND SHIPPING COSTS HAVE BEEN FORCED TO RAISE OUR PRICE BY $2 SO WOT'S COOLANT SENSOR IS NOW $31 USD ($37 USD FOR EUROPE)

So to purchase WOT’s Coolant Level Sensor (SHVCS Defeat Plug) you can submit $31 USD (includes NA shipping*) to PayPal using either THIS LINK https://paypal.me/wopontour OR from PayPal use the following email address
Code:
like_budda@shaw.ca
(just copy and paste address above) and it will be mailed out to you including complete instructions. *UK AND EUROPE PLEASE ADD $6 ($37USD total) (including complete instructions) MAKE SURE YOU ADD YOUR NAME AND MAILING ADDRESS TO THE "MESSAGE TO SELLER" FIELD IN PAYPAL

So available at this price for a limited time only as eventually they will be adding WOT's Coolant Level Sensor onto eBay (likely at a slightly higher price) at some point, but for our gm-volt.com forum members it will be available by simply submitting payment and it will be mailed out within 7 business days.

The shipment should take place within 7 business days of ordering and they are being shipped to the U.S. via "small packet" airmail service. The delivery standard for this service is 4-10 business days (I presume depending on location)

So please expect 2-3 weeks for delivery. If it's been longer than 3-weeks then PM me your name and address and I will confirm.

*Canadian orders are going via simple oversized letter postage but should be there in about the same period

ALSO please remember to add your mailing address to the PayPal "message to seller" as sometimes PayPal does not forward it.
If we had to contact you for your mailing address it will add additional shipping time obviously

HTH
WopOnTour

PS> Feel free to post any questions/comments in this thread
PSS> THANKS TO STEVERINO AND OTHERS THAT POSTED PHOTOS THAT I AM ADDING HERE
 

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#2 ·
Done. I really need this since I have NO dealer support in Honduras. I had already purchased a new sensor and harness as a preventive measure, but this solution is better.

Thanks for offering this WOT
 
#6 ·
I would not recommend by-passing a safety feature and rely on GM to honor it's warranty. This is not a after market part, its a by-pass part.

The drive motor battery coolant level sensor IS covered under the Voltec warranty, if you had one replaced that you paid for and you are under the 8/100k warranty, you need to get your money back.

5021400 Drive Motor Battery Coolant Level Sensor Replacement WARRANTY CODE: Coverage Code: V

After programming over 20 cars with the updated software, have not seen one car return for a level sensor code. The updated software is also covered under the 8/100k warranty.

If you are out of this warranty then I can see using the by-pass sensor since you have no worries of warranty coverage being denied due to tamper.
 
#7 · (Edited)
I would not recommend by-passing a safety feature and rely on GM to honor it's warranty. This is not a after market part, its a by-pass part.

The drive motor battery coolant level sensor IS covered under the Voltec warranty, if you had one replaced that you paid for and you are under the 8/100k warranty, you need to get your money back.

5021400 Drive Motor Battery Coolant Level Sensor Replacement WARRANTY CODE: Coverage Code: V

After programming over 20 cars with the updated software, have not seen one car return for a level sensor code. The updated software is also covered under the 8/100k warranty.

If you are out of this warranty then I can see using the by-pass sensor since you have no worries of warranty coverage being denied due to tamper.
Your dealership may have been covering this repair under warranty. But that has not been the case for many dozens of people posting here and elsewhere (Facebook Volt Group) each and every month. Most have had to pay for the repairs if they are off the 3-YEAR Bumper to Bumper.
Yes, there are exceptions but a great many have had to fork out as much as $500 for 4hrs. of labor and a $30 part.

For years, I've been telling people on here to go back and complain and go back and ask for warranty coverage, but they end up fighting for weeks to try to get reimbursed, and some just flatly refused by the dealer/GM.
We used to be able to get Volt Advisors involved to help but that program is a skeleton of what it once was.

Meanwhile their car is tied up for many hours (or days) while technicians perform detailed diagnosis on the P0AA6 loss of isolation DTC that is automatically triggered with the P1FFx series of DTCs, (without an actual isolation issue detected) THEN there's battery coolant pressure tests, electrical diagnosis of the system, unsuccessful attempts to clear the DTCs, all in an attempt to remedy the issue but eventually discovering the flakey coolant level sensor is bad (it's failure is intermittent I now have 12 of the defective ones on my desk) and eventually (only if they call TAC or actually READ the P1FFF DTC chart) a reflash of HPCM2 is necessary to reset everything.
It's ridiculous. Enough is enough.

BTW DESPITE WHAT YOU SAY THERE IS NO SUCH SOFTWARE UPDATE! (what all the dealers have been saying falsely)
THERE IS NO BULLETIN STATING SUCH AN "UPDATE" EXISTS.

Read through the P1FFF DTC chart. An HPCM2 reflash is simply what is required to clear the code and the message! lol
Nothing changes! (it's often the exact same software Cal IDs and CVNs)
We have had people on here have this issue occur 3 times in 1 year! (and each time the sensor is replaced and the same ridiculous labor charges for diagnosis and of course yet another "update" lol)

...and you yourself have done only 20 cars? gravy train!! lol (love to see that 1st work order ;) )

FYI we have already had our lawyers check out the stipulations of the Magnuson Moss act regarding this device. (feel free to do the same)
http://www.mlmlaw.com/library/guides/ftc/warranties/undermag.htm
It is officially an "aftermarket replacement part" and it's use will not affect any aspect of the manufacturers warranties.

A similar Magnuson Moss challenge occurred with the ERDTT bypass harnesses and it too was deemed as such.

So, I suggest you don't sweat the details ;)

*I know you're trying to help, but in this case you're way off base!
Please use a PM if you wish to communicate with me on this issue any further...


WOT
 
#8 ·
Count me as being on board for WOT's preventative measure solution for this Gen1 lingering issue. I would much rather avoid having to make the 'drive of shame' into the GM service dept. just to have the HPCM2 reprogramed in order to clear the latched DTCs caused by a failing sensor!:D
 
#9 · (Edited)
...Feel free to post any questions/comments in this thread...
Are there any data that suggests that these failures correlate with mileage, time, weather, road surface, etc? Are there any data suggesting that once a unit has been in service for a while it is more or less likely to fail? Do the failure rates tend to follow a bathtub curve, j-curve, etc?

Thanks in advance.

KNS

Edit: Is there a warranty on the part?
 
#11 · (Edited)
Are there any data that suggests that these failures correlate with mileage, time, weather, road surface, etc? Are there any data suggesting that once a unit has been in service for a while it is more or less likely to fail? Do the failure rates tend to follow a bathtub curve, j-curve, etc?

Thanks in advance.

KNS
AFAIK GM has not been analyzing these failures whatsoever. To the best of my knowledge the failed sensors ar not being requested by the GM warranty parts center and simply destroyed by the dealership.

However I have "collected" now 15 of the failed units (more are coming with a little help from my friends) and the failure appears to be within the internal bussing that is encapsulated in a sealed "potting" epoxy (a royal PITA to dissect let me tell you) of the reed switch.

IMO there is either an internal cold solder issue or mechanical vibrations and possibly temperature fluctuations are instigating the failures. The real problem is the issue often manifest intermittently. So when the tech checks the circuit using a DVOM or GDS2 may appears OK. These almost always result in a "comeback" for repeat failures.

But I have "close acquaintances" that have had a new sensor fail in 3-6 months TWICE! (which essentially instigated my desire to solve this issue once and for all, as in many cases it was I that turned them into Volt fans) :p

WOT
 
#10 ·
Could an app like Torque Pro be used to clear a SHVCS message via an OBDII adapter? Then if this error did pop up, we could clear it, order the part, and install it? Or is the only way to clear the SHVCS code at the dealer?
 
#14 ·
My ELR has a 40-month/50k B-T-B warranty. Why would I do this before it is out of warranty?
 
#17 ·
service high voltage charging system

Posted earlier about this message. Had it in June, the dealer reprogrammed battery module and another. Message returned again a month and a half later. Modules could not be programmed. After being in the dealership for 16 days, dealer replaced the following items
22922224 Sensor $11.00
22911435 module $167.00
22911435 relay $569.00
50300210 block relay Price ?
12378390 coolant
God knows what the labor would cost.
Cost me nothing since the voltec system is under warranty for 8 years (volt is a 2012)
I'll bet that the entire problem was the $11.00 sensor. (same sensor used in the washer fluid container!!)
Prices were gotten off of Gene Culley's site.
 
#18 · (Edited)
Posted earlier about this message. Had it in June, the dealer reprogrammed battery module and another. Message returned again a month and a half later. Modules could not be programmed. After being in the dealership for 16 days, dealer replaced the following items
22922224 Sensor $11.00
22911435 module $167.00
22911435 relay $569.00
50300210 block relay Price ?
12378390 coolant
God knows what the labor would cost.
Cost me nothing since the voltec system is under warranty for 8 years (volt is a 2012)
I'll bet that the entire problem was the $11.00 sensor. (same sensor used in the washer fluid container!!)
Prices were gotten off of Gene Culley's site.
It's a bona-fide epidemic!
Many dealers are replacing the relay junction block and/or battery coolant heater out of desperation in attempting to repair the P0AA6 that is automatically triggered to accompany the P1FFx series of DTCs for the coolant level sensor. They are then fooled by a changing isolation voltage readings displayed when the battery coolant heater is manually engaged by the scan tool (which is NORMAL behaviour actually)

The reality is it isn't actually detecting a "loss of isolation" as the P0AA6 seems to indicate simply because the DTC is being triggered due to the "Service High Voltage Charging System" software NOT the actual "conditions for setting" a P0AA6

Unless your coolant WAS actually low, I too suspect the level sensor is all it was! ;)
Glad to hear you had it covered under warranty, but the 16 days must have been hell.
Here's a potential low-cost and painless solution to prevent future occurrences


http://gm-volt.com/forum/showthread...OTs-SHVCS-DEFEAT-DEVICE&p=3573370#post3573370
Hot off the press! ;)
WOT
 
#19 ·
I too have had this repaired as a warranty item after 3/36K is over with, as it is part of the battery management system per my dealer. (been real good people BTW) Was lucky and I needed a wash and oil change anyway full service synthetic for $58.

From a ladder logic sort of perspective, this failed part is rarely detectable and when a out of parameter condition occurs it sets a non clearable DTC which points to all the wrong things. This looks like a pretty major software fault to me.

These sorts of error conditions should always be easily detectable, clear themselves with a part replacement and a clear scan codes. What was GM thinking when they designed this fix and production change back in 2012? DUH!
 
#35 ·
Money sent! My 2011 hasn't had this issue yet, and now it never will! Thanks for getting this done, WOT!
I guess you didn't read post #13 in this thread...

...About the only cars that this bypass plug won't work with are 2011s (and a few early 2012s) that may not have had the battery structural enhancement (side impact) campaign #11342 completed. THEY DONT HAVE A COOLANT LEVEL SENSOR OR THESE DTCS! ;)
WOT
KNS
 
#23 ·
Good Morning!

I just wanted to take a moment to advise all of you of the following information, which is published in the warranty booklet:

"This warranty does not cover any damage or failure resulting from modification or alteration to the vehicle's original equipment as manufactured or assembled by General Motors. Examples of the types of alterations that would not be covered include cutting, welding, or disconnecting of the vehicle's original equipment parts and components."

"Additionally, General Motors does not warranty non-GM parts, calibrations, and/or software modifications. The use of parts, control module calibrations, software modifications, and/or any other alterations not issued through General Motors will void the warranty coverage for those components that are damaged or otherwise affected by the installation of the non-GM part, control module calibration, software modification, and/or other alteration."

If you have any questions or would like to discuss this further, please don't hesitate to send our team a private message, at your convenience.

Kayla K.
Chevrolet Customer Care
 
#24 ·
SERVICE HIGH VOLTAGE CHARGING SYSTEM



Why doesn't GM redesign the sensor. This sensor is used in all GM cars in the windshield wiper reservoir, that's cold water. In the battery reservoir water may be hotter, this could lead to sensor failure. I really don't want to add mods to my Volt , but I just got my car back after 15 days, I did not enjoy that. Approx. $1000 worth of parts were changed including that $11 sensor, which may have been the problem all along
 
#27 ·
Rather odd that this Chevrolet Customer Svc account is radio silent for the last 3 weeks and then suddenly decides to pop up in this thread?:confused:

Morley Companies, Inc. Employee Reviews for Chevrolet Volt Advisor

From what I understand, this account is shared between the staff contracted by GM to operate the Volt/Spark/ELR Advisor team(s) and aren't GM employees. I hope there would be no need for lawyers.
 
#28 · (Edited by Moderator)
Glad for all that have not experienced this issue but I have it nearly every 10k miles. Dealer guesses something new every time and says it's fixed, it's not. It gets more expensive each time too! First it was free, then a reprogram was 100 something (Incredible how they claimed the SHVCS message doesn't relate to the Voltec warranty!), now they wanted 300+ to replace a wiring harness that was spliced in place to add this stupid thing in the first place. It could be the harness, but the more I inspect it I'm pretty sure it's just this sensor.

My car has only had 1 other visit which was not related to this issue, so 75% of my visits are due to this. As WOT has stated there is no reimbursement for getting me to the dealer, no loaner car, and no coverage for the gas my truck takes to make my commute (which I'm lucky to have at least).

This has hugely impacted my opinion on the reliability of this car and faith in Chevy to make a good car. 1 visit to the dealer in 50k? Good car! 4 visits to the dealer in 50k? Junk.

Totally agree. I've even called the dealer for family members and attempted to intervene saying "just replace the damn sensor and reprogram HPCM2 please, that's all, we'll pay. Only to have that brand new sensor fail again a few months later! Grrrrrrr - WOT
 
#29 · (Edited by Moderator)
Burden of proof is on the manufacturer to prove that an after-market part was actually cause of an issue that occurs after the part is installed. If you owned a car, installed a hitch to only carry your bike, and your engine blows down the road, the manufacturer can't just go "Oh, you installed a hitch, so you must have been towing things that exceeded the maximum rated tow capacity of the car, so we're not replacing your engine under warranty".

Now if you installed a hitch, then posted a video on Youtube of towing a 1,500 boat with your non-tow rated car, and THEN your engine blows....that is another story.

BINGO! - WOT
 
#30 · (Edited)
My 2013 has not had this issue yet, but it sounds to me like the "WOTs Coolant Level Sensor" is a good preventative measure. I plan to order one.

A few questions:

1. With this new sensor installed, if there is an actual drop in the coolant level, will any warning messages be triggered, or does it just keep the software happy, thinking the level is OK when maybe it isn't? If the latter is the case, I understand why you would want to check the coolant level on a regular basis. As I recall, the original level sensor was added to address a concern where coolant may be leaking internal to the battery and not be visible on the ground below the vehicle.

update: After re-reading page 1, it sounds like this device is plugged into the wiring harness to 'mimic' a good sensor with full fluid level and does NOT measure the fluid level in the coolant tank.

2. Could the process of installing the new sensor be reversed, and the old sensor re-installed without triggering additional fault codes?

update: I think maybe it could, assuming the process is done while the vehicle is 'asleep', correct?

I agree that a failing level sensor should not result in one or more battery high voltage isolation faults. The software SHOULD be (but apparently isn't) smart enough to determine the 'root cause' of the failure and suppress any 'downstream' faults caused by the root cause. I have worked on airplane maintenance systems that did this.
 
#31 · (Edited)
My responses added IN RED below but it looks like you've answered most of them yourself! ;)

My 2013 has not had this issue yet, but it sounds to me like the "WOTs Coolant Level Sensor" is a good preventative measure. I plan to order one.

A few questions:

1. With this new sensor installed, if there is an actual drop in the coolant level, will any warning messages be triggered, or does it just keep the software happy, thinking the level is OK when maybe it isn't? If the latter is the case, I understand why you would want to check the coolant level on a regular basis. As I recall, the original level sensor was added to address a concern where coolant may be leaking internal to the battery and not be visible on the ground below the vehicle.

update: After re-reading page 1, it sounds like this device is plugged into the wiring harness to 'mimic' a good sensor with full fluid level and does NOT measure the fluid level in the coolant tank.Correct!

2. Could the process of installing the new sensor be reversed, and the old sensor re-installed without triggering additional fault codes?

update: I think maybe it could, assuming the process is done while the vehicle is 'asleep', correct? Yes, and the included instructions outline exactly how to do that, however they also mention to simply disconnect the 12V negative post from the AGM battery as an alternative. However for those in States that have emissions testing that could reset all your I/M Flags and cause a failure if you have the car tested and haven't been able to run it on ICE extensively

I agree that a failing level sensor should not result in one or more battery high voltage isolation faults. The software SHOULD be (but apparently isn't) smart enough to determine the 'root cause' of the failure and suppress any 'downstream' faults caused by the root cause. I have worked on airplane maintenance systems that did this.
Thanks for the support. They simply went overboard and the behavior and diagnostic process is so convoluted and abnormal the technicians will often simply overlook the flaky sensor and spend a lot of time looking for something more complicated.

I simply HAD to do something just to save face with my own large extended family and friends that I've put into Volts with my endorsement which they all trust (like 33 cars since 2011)!

It's been embarrassing! So I had to share!

WOT
 
#33 ·
What great timing! This warning came on for the 7th time a few days ago. That makes at least three times in the past year so the rate might be increasing. The dealer has never replaced the sensor but resets the flag for free...which would have really annoyed me if they charged for it.
It's so frustrating since I know nothing is wrong with the car but I need to take time off from work, drive the hour to the dealership and then spend the rest of the afternoon waiting around. If it wasn't for this issue with the Volt, I would have only been to the dealer twice for the normal wear and tear over the past 61K miles.
It saddens me that GM can't fix a simple software and/or sensor issue that's plagued early Volts models for years. They've had enough time to correct this so now I'm going to fix it myself!
I keep getting letters in the mail from some law firm who wants me to join a class action lawsuit against the Volt. They say it's a lemon. I wouldn't go that far but every time I miss work because of this issue, I think about it. I'll just have to use one more personal day at the dealership now. Thanks WOT!
 
This post has been deleted
#34 · (Edited)
Purchased.

2 1/2 years in, I've not had a lot of trouble with my '14. $29 seems like a reasonably priced insurance measure to avoid this sort of silliness. Besides, if it's WOT approved, there's some there there. Kinda odd when a hardline company man goes 'rogue' like this.

P.S. This thread might get more clicks if you put "WOTs LEVEL SENSOR /SHVCS DEFEAT DEVICE" ahead of "SERVICE HIGH VOLTAGE CHARGING SYSTEM MESSAGE" in the title. I've been seeing this thread for 4 days and skipped it until I ran across a link in another semi-unrelated thread.
 
#38 ·
WOT I don't think anyone has addressed the issue of latch type codes for the coolant sensor. Because of this, only a GM equipped dealer can clear the issue, the issue is vague and requires a long list of diagnostics and is extremely expensive for a few dollar replacement part. The setup of this sensor should not brick the car as it does. I could understand the battery over heat codes setting a latched code but a non-latching code for the sensor would seem to be in order.

This whole issue seems to be in place to grease the dealers wallet. (OK maybe a bit extreme) but the poor diagnostic flow for this sensor does create a great expense for the owner AND GM has no fix that is more permanent than replace the sensor, reflash and hope for the best. That in turn burdens the consumer with an expensive repair for a cheap and poorly engineered part for this application.

At the very least GM should consider these repairs a customer satisfaction issue.

Oh BTW what every happened to GoodWrench lifetime guarantee for repairs made at the dealer?
 
#40 ·
Thanks a million, WOT! (But I only send 29 bucks). :)
 
#41 ·
Thanks for doing this. $29.00 is more than worth it to avoid having to deal with my local GM dealer, which is one of those dealers who will try anything to deny warranty coverage.

They tried to do it when my heater (Aux coolant pump) died and they also flat-out refused to remedy some other issues. GM took the word of the dealer and offered ZERO help. I love my Volt, but I doubt if I will ever buy another GM vehicle again.
 
#43 ·
At the dealer right now waiting for them to finish the diagnosis of this issue. This is the third time I've been here this year and the 7th time since I purchased the Volt new.
They came back and said the fluid level sensor needs to be replaced along with the wiring harness. All of the components they added during the recall modification they performed in 2012. They say they'll replace the fluid sensor but the wiring harness will be $460 (down from $700 they normally charge). I refused they payment for the wiring harness and they're currently trying to get it covered under warranty.
I ordered this sensor bypass from WOT last weekend but if the wiring harness is bad, I don't think it will help. It seems strange to me that they wouldn't cover the repair of the wiring harness considering this modification most likely harmed it. I might have to do some exploring of the wiring harness when I do the WOT modification to see what they actually did.
 
#44 · (Edited)
Unfortunately it's somewhat normal for the dealer to start chasing connections and the harness if they have replaced the coolant sensor before.
They have a hard time coming to terms that the replacement sensor has failed so quickly. (not typical)
Instead they should be diagnosing and replacing the sensor for free (GM parts warranty is 1 year) BUT if they can point the finger at something else, "well it's your car" (and problem) prevails.

In many cases I have been involved with there is nothing wrong with the harness even on the campaign'd 2011s and 2012s.
However they cant even unplug the sensor to test the circuit without triggering the latched codes, initiating a new round of WTF? and having to reprogram HPCM2 AGAIN! (trust me I went around and around in that cycle a few times)

Really the only DTC that doesn't result in this "latched" condition is IF you actually just have low coolant , setting a P1FFE
With this single code set alone, you can actually top up the coolant, and clear the code normally. These cases however have been rare, and IF someone simply being consciences happens to unplug the sensor (with the car ON) during the service, well, I think you know what happens.

In any case if you get the car back with the message no longer being displayed. Just install WOTs coolant level sensor as per the included instructions and you wont have to bother with this again. ;)

WOT
 
#46 ·
My first sensor failed while towing up a steep grade. I made the mistake of getting it fixed at the dealer because they told me a wiring harness needed to be replaced, which I looked up the part# for and was a large job. Afterward I looked at their work and they really only spliced in two wires going to the new sensor for $320.78.

A few weeks later I was climbing a steep grade full throttle at 27 MPH (propulsion power reduced) and I got the SHVCS light on again. Using the VCX Nano I see that its P1FFF Isolation loss/Coolant level sensor.

I am NOT HAPPY with GM.

I just sent the 29$, what a bargain!
 
#47 ·
Checking in to let WOT know the plug has been received and installed on my Gen1 as of this morn.

My Volt is now charging following lifting the negative terminal off of the 12V AGM battery directions from the instruction notes resulting in success with NO DTCs currently latched!;)
 
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