Unknown. Toyota changes convention from model to model and year to year. I can't remember. No idea what they did on the GM packs.

You can pinpoint any block to 2 pairs of modules, i.e., block 4 is the 4th pair from either end.

Try to pick mirrored blocks, i.e., one block is weak, but the mirrored block at the other end of the pack is strong, e.g., blocks 4 and 17, etc.

Affix 2X naked copper bus bars to a module's terminal ends pointing UP. Secure with terminal nut. Attach a voltmeter. Take a 12V/100A load tester, clamp onto the vertical bus bars and load test the module for 15 seconds. Record the lowest voltage observed on the attached VM (don't use VM on tester - not accurate enough).

Repeat for a total of 4 times on each module in the two blocks.

A 12V/100A load tester will put about 60A on a 7.2V module. The module pair with the lowest combined voltage is the weaker block. Ultimately, you should be able to determine which end is block #1.

 

Thank you for your input, I was also thinking of using the 12V/100A load tester I have on a block, that seems like the best way to do it, and ya the volt meter on it is not very accurate. I'm gonna look at the service information now and see what it has but i'm not holding my breath. It is interesting, this pack has 200k on it, and its the modules in the middle that failed, not a coincidence, definitely from heat, just like you were saying, the cooling is very important!

 

The extra 2.5V on the block vs. a 12V will put a LOT of strain on the tester, AND having the terminals in such close proximity to one another will make it very easy to short them together. 5 minutes longer for better results.

it will also help you further isolate an issue if only ONE of the modules is bad within the block.

 

I found it, I can't post the picture because my screen shot function isn't working on my computer and its only in pdf format. It starts from the negative contactor side, the fan side, ends the count on the positive contactor side, the computer side.

 

That's consistent with Gen2 Prius with regards to the computer end (#1 opposite computer). IIRC, Gen 1 and Gen 3 are the opposite (counted from computer), and I hate working on Camrys to the point that I just don't give a poo.

Given that I test each module in detail, I get more info than Techstream can give, so I don't need correlation between blocks and position. I should probably keep that stuff in my head, but I forget my kids' names sometimes...

 

So the plot thickens... The hybrid battery was definitely bad, I confirmed that through logging data while driving the truck, had as high as a 3.6v difference between the highest and lowest blocks. I tried just replacing the 6 modules that were bad but when I put the pack back in it had the same DTC P0BBD "hybrid battery pack voltage variation limit exceeded" I logged more data driving, and the problem was then that the modules I had replaced were performing too much better than all the old ones, the old ones voltage drop was 1.3v lower than the new modules, just enough to throw the code. So, I rebuilt the entire pack using modules from 2 gen 2 prius packs that were both good packs, came out of running vehicles, no bad modules, tested them in my prius, had the data from TS, both had similar capacity and IR. So the rebuild worked, drives great, goes into battery mode and everything, voltage variation was about 0.5v under heavy load. When I did the first diagnostic on this vehicle I got some other codes for the power steering and a parasitic electrical load on the 12v system. The "service hybrid system" and "service power steering" comes up on the DIC. I did some digging through the GM service information, turns out there was a "special coverage adjustment" that affects all the GM 2 mode hybrids for the accessory power module having problems in cold weather (i'm in MI and it has been pretty darn cold lately). I should mention they have an aftermarket alarm system installed which I believe could be the cause of the parasitic drain; it could also be because the APM is not functioning properly. This special coverage adjustment is only good for 10 years or 150k, I spoke with GM TAC and they said I should talk to the dealer they bought it from, I explained that the customer wants to trade in the vehicle to buy another GM so maybe they could work something out, TAC said the dealer can decide if they will do that or not. So, since its already almost 7:00pm here, i'm going to tell the customer whats going on and talk to the dealer tomorrow; hopefully we can work something out because this special coverage adjustment describes exactly whats going on with this truck, i'm pretty confident that the APM needs to be replaced. I should also note that the 12v battery terminals were this quick connect type and the positive terminal could be rotated when it was supposed to be tight, so I replaced the terminals and charged the 12v battery.

The codes for the EPSM are: C056D (EPS ECU Hardware) and C0895 Control module voltage- symptom #12 low input voltage (intermediate voltage is less than 26v) and symptom #03 low voltage (intermediate voltage is less than 40v) voltage should be between 37.5v-60v. So I think whats happening is when the APM is cold and vehicle is started, the APM isn't working and the 42v EPS is only getting 12v from the battery, which puts the "service hybrid system" and "service power steering" warnings on the DIC, once the APM warms up it starts working properly supplying 42v to the EPS and the EPS works fine. I also found through reading the service information that these cars have two DC-DC converters (APM) a bi-directional 300v-12v APM and a mono-directional 300v-42v APM for the EPS. So the bi-directional one must be functioning properly or the 12v battery would be completely drained. It's possible that the EPS system is pulling more power than the 12v APM can supply while the vehicle is warming up, which could maybe explain the parasitic drain, if the vehicle wasn't run for long enough for the 12v APM to replace the power that was drained by the EPS. I still have to do a full test to see if my theory is correct and to also isolate the parasitic drain, if it's being caused by the alarm system or something else.

Here's the full text from GM:

#14262: SPECIAL COVERAGE ADJUSTMENT - ACCESSORY POWER MODULE MAY NOT INITIALIZE
IN COLD TEMPERATURE (OCT 27, 2014)

Document ID#
4007140
#14262: SPECIAL COVERAGE ADJUSTMENT - ACCESSORY POWER MODULE MAY NOT INITIALIZE IN
COLD TEMPERATURE (OCT 27, 2014)
Subject: 14262 – Special Coverage Adjustment — Accessory Power Module May Not

Initialize in Cold Temperature
Models: 2009-2013 Cadillac Escalade
2009-2013 Chevrolet Silverado LD
2008-2013 Chevrolet Tahoe
2009-2013 GMC Sierra LD
2008-2013 GMC Yukon
Hybrid 2-Mode (HP2) Vehicles

Condition
On some 2008-2013 model year Chevrolet Tahoe and GMC Yukon, and 2009-2013 model year Cadillac Escalade,
Chevrolet Silverado LD, and GMC Sierra LD hybrid 2-mode (HP2) vehicles, the accessory power module (APM) may
not initialize when the vehicle is started in cold temperatures and the APM is cold. Once the APM warms up, it will
initialize and perform as designed. However, during the time that the APM is not operational, it could result in a
loss of power steering assist and the battery may not charge. If this condition occurs, the Service Power Steering,
Service Hybrid System, or Service Battery Charging System message will appear in the driver information center,
the malfunction indicator lamp and red battery telltale may illuminate, and DTC U1821 and U182A will be present.
Special Coverage Adjustment
This special coverage covers the condition described above for a period of 10 years or 150,000 miles (240,000
km), whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership.
Dealers are to replace the APM. The repairs will be made at no charge to the customer.
For vehicles covered by Vehicle Service Contracts, all eligible claims with repair orders on or after October 27,
2014, are covered by this special coverage and must be submitted using the labor operation codes provided with
this bulletin. Claims with repair orders prior to October 27, 2014, must be submitted to the Service Contract
provider.
Vehicles Involved
All involved vehicles are identified by Vehicle Identification Number on the Applicable Warranties section in GM
Global Warranty Management system. Dealership service personnel should always check this site to confirm
vehicle involvement prior to beginning any required inspections and/or repairs. It is important to routinely use this
tool to verify eligibility because not all similar vehicles may be involved regardless of description or option content.
Parts Information
For U.S. and Canada: The parts required for this program are on restriction through the GM Technical Assistance
Center (TAC). If diagnostics lead to the replacement of the accessory DC power control module, please contact
TAC at telephone number US 1-877-446-8227 (Action Center prompt or Hybrid prompt) or Canada 1-800-263-
7740 for English or 1-800-263-7960 for French.
For Export: If the described condition has been confirmed using the diagnostics listed in the service procedure,
please contact CCA’s Export Order Fulfillment group to place the order on your behalf.
Part Number Description Quantity/Vehicle
24251562 Accessory DC Power Control Module 1

19207978 Seal Kit 1
Service Procedure
1. Determine if the accessory DC power control module (APM) requires replacement.
Note: One or more of the conditions listed below will be present. These conditions may occur shortly after
start up after a cold soak in cold ambient temperatures at approximately 12oF to -4oF (-11oC to -20oC).
Service Powering Steering message displayed on the Driver Information Center (DIC)
Service Hybrid System message displayed on the DIC
Charging system indicator lamp on
Loss of power steering assist
Loss of 12 volt battery power
When checking the vehicle for DTCs, the Accessory DC Power Control Module may report U1821,
U182A, and C0895 active or in history
If the APM does not require replacement, no further action is required. Inform the customer that
any additional diagnosis and repairs are not covered under this special coverage.
If the APM requires replacement, proceed to step 2.

2. Remove the APM. Refer to Accessory DC Power Control Module Removal and Installation in SI.
3. Install a new APM. Refer to Accessory DC Power Control Module Removal and Installation in SI.
4. Program the APM. Refer to Accessory DC Power Control Module Programming and Setup in SI.
Customer Reimbursement – For US
Customer requests for reimbursement of previously paid repairs to correct the condition described in this bulletin
are to be submitted to the dealer by November 30, 2015, unless otherwise specified by state law. If this is not
convenient for the customer, they may mail the completed Customer Reimbursement Request Form and all
required documents to the GM Customer Assistance Center. Repairs must have occurred within the 10 years of the
date the vehicle was originally placed in service, or 150,000 miles, whichever occurs first.
All reasonable and customary costs to correct the condition described in this bulletin should be considered for
reimbursement. Any questions or concerns should be reviewed with your GM representative prior to processing the
request.
When a customer requests reimbursement, they must provide the following:
A completed Customer Reimbursement Request Form. This form is mailed to the customer or can be
obtained through GM GlobalConnect.
The name and address of the person who paid for the repair.
Paid receipt confirming the amount of the repair expense, a description of the repair, and the person or
entity performing the repair.
Important: GM requires dealers to approve or deny a reimbursement request within 30 days of receipt. If a
reimbursement request is approved, the dealer should immediately issue a check to the customer and submit an
appropriate warranty transaction for the incurred expense. If a reimbursement request is denied, the dealer MUST
provide the customer with a clear and concise explanation, in writing, as to why the request was denied. The
bottom portion of the Customer Reimbursement Request Form may be used for this purpose. If the denial was due
to missing documents, the customer can resubmit the request when the missing documents are obtained, as long
as it is still within the allowed reimbursement period.
Warranty transactions for customer reimbursement of previously paid repairs are to be submitted as required by
GM Global Warranty Management. Additional information can also be found in Warranty Administration Bulletin 11-
00-89-004.
Customer Reimbursement – For Canada and Export
Customer requests for reimbursement of previously paid repairs to correct the condition described in this bulletin
are to be submitted to the dealer prior to or by November 30, 2015. Repairs must have occurred within the 10
years of the date the vehicle was originally placed in service, or 240,000 kilometers, whichever occurs first.
When a customer requests reimbursement, they must provide the following:
Proof of ownership at time of repair.
Original paid receipt confirming the amount of unreimbursed repair expense(s) (including Service Contract
deductibles), a description of the repair, and the person or entity performing the repair.

All reasonable and customary costs to correct the condition described in this bulletin should be considered for
reimbursement. Any questions or concerns should be reviewed with your GM representative prior to processing the
request.
Courtesy Transportation – For US and Canada
The General Motors Courtesy Transportation program is intended to minimize customer inconvenience when a
vehicle requires a repair that is covered by the New Vehicle Limited Warranties. The availability of courtesy
transportation to customers whose vehicles are within the warranty coverage period and involved in a product
program is very important in maintaining customer satisfaction. Dealers are to ensure that these customers
understand that shuttle service or some other form of courtesy transportation is available and will be provided at
no charge. Dealers should refer to the General Motors Service Policies and Procedures Manual for Courtesy
Transportation guidelines.
Warranty Transaction Information
Submit a transaction using the table below. All transactions should be submitted as a ZREG transaction type,
unless noted otherwise.
Note: To avoid having to "H" route the customer reimbursement transaction for approval, it must be submitted
prior to the repair transaction.
Labor
Code Description Labor
Time
Net
Item
9900076 Diagnostic Time Only – No Repair Required 0.1-0.3 N/A

5010220
Accessory DC Power Control Module Replacement – For use with vehicles still covered
under warranty 1.5
Add: Diagnostic Time 0.1-0.3

9900077
Accessory DC Power Control Module Replacement – For use with vehicles no longer
covered under warranty 1.5

N/A
Add: Diagnostic Time 0.1-0.3
9900078 Customer Reimbursement Approved 0.2 *
9900079 Customer Reimbursement Denied - For US dealers only 0.1 N/A
* The amount identified in “Net Item” should represent the dollar amount reimbursed to the customer.
Customer Notification
General Motors will notify customers of this special coverage on their vehicles (see copy of typical customer letter
included with this bulletin - actual divisional letter may vary slightly).
November 2014
Dear General Motors Customer:
As the owner of a 2008-2013 model year Chevrolet Tahoe or GMC Yukon, or 2009-2013 model year Cadillac
Escalade, Chevrolet Silverado LD or GMC Sierra LD hybrid 2-mode vehicle, your satisfaction with our product is
very important to us.

This letter is intended to make you aware that on some 2008-2013 model year Chevrolet Tahoe and GMC Yukon,
and 2009-2013 model year Cadillac Escalade, Chevrolet Silverado LD, and GMC Sierra LD hybrid 2-mode vehicles,
the accessory power module (APM) may not initialize when the vehicle is started in cold temperatures and the APM
is cold. Once the APM warms up, it will initialize and perform as designed. However, during the time that the APM
is not operational, it could result in a loss of power steering assist and the battery may not charge. If this condition
occurs, the Service Power Steering, Service Hybrid System, or Service Battery Charging System message will
appear in the driver information center, the malfunction indicator lamp and red battery telltale may illuminate, and
diagnostic trouble code U1821 and U182A will be present.
Do not take your vehicle to your GM dealer as a result of this letter unless you believe that your vehicle has the
condition as described above.
What We Have Done: General Motors is providing owners with additional protection for the condition described
above. If this condition occurs on your 2008-2013 model year Chevrolet Tahoe or GMC Yukon, or 2009-2013
model year Cadillac Escalade, Chevrolet Silverado LD or GMC Sierra LD hybrid 2-mode vehicle within 10 years of
the date your vehicle was originally placed in service or 150,000 miles (240,000 km), whichever occurs first, the
condition will be repaired for you at no charge . Diagnosis or repair for conditions other than the condition
described above is not covered under this special coverage program.
What You Should Do: If you believe that your vehicle has the condition described above, repairs and adjustments
qualifying under this special coverage must be performed by a General Motors dealer. You may want to contact
your GM dealer to find out how long they will need to have your vehicle so that you may schedule the appointment
at a time that is convenient for you. This will also allow your dealer to order parts if they are not already in stock.
Keep this letter with your other important glove box literature for future reference.
Reimbursement: If you have paid for repairs for the condition described in this letter, please complete the
enclosed reimbursement form and present it to your dealer with all required documents. Working with your dealer
will expedite your request, however, if this is not convenient, you may mail the completed reimbursement form
and all required documents to Reimbursement Department, PO Box 33170, Detroit, MI 48232-5170. The
completed form and required documents must be presented to your dealer or received by the Reimbursement
Department by November 30, 2015, unless state law specifies a longer reimbursement period.
If you have any questions or need any assistance, just contact your dealer or the appropriate Customer Assistance
Center at the number listed below.

 

Way over my head. I got nothing for you.

Hopefully, Hillbilly will check in...

 

They're satisfied with the battery being repaired, at this point they don't want to put more money into it, the APM costs $509 new, takes 1.5 hours to replace according to GM, wouldn't make sense to get a used one because it would probably have the same problem. They said they'll never buy a hybrid again, good job GM!

 

I can't quickly find the details. IIRC, it's over 200K miles, and they're not the original owners. On a vehicle with > 200K miles, it's kinda hard to point the finger of blame at GM.

Unfortunately, most used hybrids are a poor choice when compared to the value of a used non-hybrid. Having two propulsion systems with many additional failure points, it's unlikely that the purchaser of a 150K mile used hybrid will NOT have a significant hybrid related expense within the next 50K miles.

I vigorously discourage friends and family from purchasing used hybrids unless they're okay with spending a couple thousand dollars within the 30 days following purchase - not that it's going to happen, but it's very possible if any of the major systems fail.

 

NOTE: the 2-Mode 42V DC is powered by the HV battery.+