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Service Information


2009 Chevrolet Silverado - 4WD | Sierra, Silverado VIN C/K Service Manual | Document ID: 2743912
#PI0310B: Loss of Communication with Allison TCM, Intermittent Transmission Hesitation, Reduced Torque, Range Inhibit, Clunk, Stuck in Gear or Neutral, Wont Shift, DTC P0880 and/or U0101 Set - (Dec 2, 2011)

Subject:Loss of Communication with Allison Transmission Control Module (TCM), Intermittent Transmission Hesitation, Reduced Torque, Range Inhibit, Clunk, Stuck in Gear or in Neutral, Won't Shift, DTC P0880 and/or U0101 Set (Inspect for Electrostatic Discharge (ESD) From Aftermarket Serpentine Belts and/or Added Equipment, Install OEM Belt, Relocate TCM)

Models:2007-2012 Chevrolet Silverado
2007-2012 GMC Sierra
Equipped with Allison® A1000 Automatic Transmission RPO MW7

Attention:Please review the latest version of Corporate Bulletin Number 04-06-04-054B: Info - Non-GM Parts and Accessories (Aftermarket), for information regarding GM's policy on the use and installation of aftermarket components.​

This PI is being revised to add G102 information to the Condition/Concern and Recommendation/Instructions. Please discard PI0310A. The following information may be helpful if the vehicle exhibits the symptoms described in this PI.
Condition/Concern


Some customers may comment that the transmission will intermittently hesitate, clunk, gets stuck in gear or in neutral, won't shift, or experience reduced torque or range inhibit.
The technician may observe on a scan tool DTC P0880 and/or DTC U0101 set as Current or in History.
This condition may be caused by:

• Resistance in the G102 ground connection on the side of the engine block.
• During normal servicing, the OEM General Motors serpentine belt was replaced by an aftermarket serpentine belt.
• An aftermarket serpentine belt was intentionally installed, due to dimension changes from added aftermarket equipment such as a second alternator or clutch pump installed by an upfitter.​

Certain brands of replacement aftermarket serpentine belts are made of compounds that will reduce the opportunity for audible belt noise, however these compounds can generate significant amounts of electrostatic charge on their surface. This electrostatic charge can discharge and cause DTC P0880 and/or DTC U0101 to set and be accompanied by any of the above symptoms.
Recommendation/Instructions


Important: DO NOT replace the transmission control module (TCM) until the root cause of the problem has been properly resolved. The TCM ONLY NEEDS to be replaced if it has incurred permanent damage, such as hard failed codes, complete loss of communication or other erratic behavior that continues to exist AFTER completing the following steps.

1. Perform the Diagnostic System Check - Vehicle.
⇒If DTC P0880 and/or U0101 are set as Current or in History, and/or the above symptoms are observed, proceed to Step 2.
⇒If DTC P0880 and/or U0101 are not set as Current or in History, and/or the above symptoms are not observed, refer to > Transmission > Automatic Transmission - Allison > Diagnostic Information and Procedures in SI.
2. Turn OFF the ignition.
3. Disconnect and inspect the G102 wire terminal and connection for looseness and corrosion. Clean any corrosion from the wire terminal and the surface of the engine block with a wire brush.
4. Apply dielectric grease to the wire terminal and engine block surface. Connect the G102 wire terminal and secure properly.
5. Inspect the engine for an aftermarket serpentine belt due to service replacement or added aftermarket equipment from an upfitter.
⇒If an aftermarket serpentine belt is installed on the original serpentine system, without added aftermarket equipment installed on the engine, replace the serpentine belt with an OEM General Motors serpentine belt. Refer to Drive Belt Replacement in SI.
⇒If an aftermarket serpentine belt is installed because of added aftermarket equipment installed on the engine, proceed to Step 6.​

Important: DO NOT relocate the transmission control module (TCM) if aftermarket equipment HAS NOT been installed on the engine.Relocate the TCM ONLY if an additional or longer accessory drive belt has been installed on the engine, resulting in the drive belt being closer to the TCM. Relocating the TCM on a vehicle that has not been modified, WILL NOT correct the DTCs and may result in a comeback.
6. Relocate the TCM (1) to the top of the UBEC cover and secure it using a heavy duty adhesive or Velcro® “hook and loop fastener”. DO NOT use push pins as fasteners, they will compromise the water resistance of the UBEC cover.​

Velcro® is a registered trademark of Velcro Industries B.V.
Allison® is a registered trademark of Allison Transmission, Inc.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

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© 2012 General Motors. All rights reserved.

 

Not heard of the static discharge but since you mention no tuner you have a DPF back exhaust system and not cat back. Next the P0101 code is a MAF sensor code. It may be a fluke but do you still have the stock air box on the truck and using a standard dry core air filter. Not an oiled type K&N air filter?

Do you still have the original batteries in the truck. If so one or both may be bad or nearing their end of life since you mention only happens in the morning after setting so everything is cold and these truck pull a hell of lot of current to start and up to 10 minutes after started. I suggest having each battery load tested separately not as a pair where both are connected at the same time. It would be my thinking the battery voltage is to low for some of the modules to wake up at the right time. If one battery is bad or less than half its life replace both batteries at the same time.

You can check the voltage of the batteries on eaither one before starting to see what they read. Now it may depend on the Insight you have. I have heard of some draining the battery overnight. There is a special update you have to contact Edge to get for the CS or CTS Insight versions. If the original then I know of no problems.

Brian

 

Stock air box and stock AC air filter, you are correct DPF back exhaust, only replaced the muffler and the tail pipe. Replaced both batteries with a pair of odysseys about 8 months ago. Looks like the TSB has been confirmed and is the Gator back belt is the likely culprit or at least the first thing to fix. Going to do that tomorrow and see how it goes. Strangest thing yet that i have seen with this truck. I figured a belt was a belt, ran gator backs on my LLY with no issues.

 

Looks like you can relocate TCM if you want to keep your Gatorback belt.

 

Code U101

Well to follow up i replaced the Goodyear Gatorback belt with a GM factory belt and 2 weeks plus have gone by with no issues. I guess the TSB was valid in this case. The TCM does not like the gatorback belt. Strange but at least it is fixed.

 

Well to follow up i replaced the Goodyear Gatorback belt with a GM factory belt and 2 weeks plus have gone by with no issues. I guess the TSB was valid in this case. The TCM does not like the gatorback belt. Strange but at least it is fixed.

Yes the Gator backs are a big issue. I'm glad the word is getting out. Over time it will actually damage the TCM to the point of it not working at all anymore. I'm glad you got it figured out before you got to that point.

Is your truck a dual alternator by chance? (this puts the belt closer to the TCM)

 

I know this an old thread, and the OP has indicated that his issue has been corrected by following the TSB mentioned above. It is this thread that has come up as the most relevant when I do a Google Search for the DTC: U0101 - Lost Communication with the TCM.

Therefore, I am including additional information that I have uncovered while searching for resolution. My search continued beyond what has been posted here because the TSB above does not resolve the issue on my 2009 GMC C5500 Service Truck with the LMM and Allison. My Service Truck is bone stock with the exception of adding a FASS Booster Pump to the fuel system. We generally use only GM OEM Parts on this truck. So I needed to get down to the OEM Troubleshooting, which led me to the attached PDF.

 

Thanks for the additional information, i did end up having to change the TCM last year. But i got 2 plus years after this belt issue before it went out.

 

I've just had same issues shown on initial post. 2009 GMC 3500 Duramax. I have a MiniMax programmer with DPF delete. The code was the u0101, no comm with the TCM. I don't have any aftermarket belts, I purchased an AC Delco replacement. Is it just a replace and go on or does it require special dealer programming?

 

Well I do realize this is an old thread, but in case anyone has some input. Tonight on my way home from work about 3 miles cruise set @65.....all of a sudden cruise kicks off, red brake light comes on as does amber ABS light.. and the DIC msg serv trailer brake control mod ...so i pull off, throw the V2 on it and get U0121lost comm with ABS ctrl mod and a U0100 lost comm with ECM, and a U0140 lost comm with body ctrl mod....stock fan belt whole truck is stock no tuning (yet)...... wandering if the svc traler brk mod is the problem. I did install two new rear shocks last tuesday and had to take the trlr brk box loose from the frame to get a punch through one of the mounting holes to knock out the top shock bolt for the drivers side anyway cleared the codes but my cruise didnt work the rest of the wsy home, the little yellow "on" light comes on but it will not set....hummm

 

"Service trailer brake" warning, without an ABS warning lamp, is a trailer brake issue. But any time there is an ABS issue, you will get a "service trailer brake" warning.

ITBC fault will not disable ABS, but
ABS fault will disable ITBC.

As far as cruise goes, if you have an'07.5-'10, and the cruise light enables, but the cruise won't set, the stoplamp switch has a defective set of contacts (one of three within). Can't confirm for later years.

 

Over the yrs had the SVC trlr brake msg from time to time, always clears itself. And I've read about the b/s failure causing cruise problem. I just have a hard time believing that all at the exact same time my b/s failed accompanied with my red brake idiot light ( which caused the SVC trlr brk DIC msg) and amber abs light...... however when dealing with electronics I've come to believe this IS possible..

 

Nothing in the trailer brake electronics can illuminate the BRAKE or ABS warning lamps, period.

As for the intermittent "service trailer brake" message, I'd suspect intermittent grounding of the UY2, blunt cut, 5th wheel wiring above the fuel filler neck. Before crawling under, read the RPO list in the glove box looking for UY2. If listed, you can either take the UY2 wiring offline, at the bumper trailer connector, or segregate the blunt cut wires and reseal them.

Furthermore, the contacts in the stoplamp switch for cruise enabling (disabling) will not illuminate the ABS lamp either, when they have failed. However, if the EBCM is offline (ABS light on), then the cruise control will not set, but, will enable.

At the very minimum, the ground wire to frame connection, on the body mount ear, under the driver's floorboatd, needs undone, sanded clean, reattached, and then sealed. I just cover it with rattle can black paint once I've cleaned it up.

 

Thanks for the info, years ago (about 7) I used dielectric grease in all my underbody connections, it's probably time to redo them. As far as the body ground I'll have to check that..

 

I wasn't talking underbody connectors. 5th wheel wiring is blunt cut, and the EBCM (ABS) ground is prone to minor corrosion.