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Document ID: 2074199
#PIP3605A: CTC U0101
No engine crank and no communication with TCM
Feb. 29,2008

Models affected:
2006-2007 Chevrolet Silverado Classic
2007-2008 Chevrolet Silverado
2006-2007 GMC Sierra Classic
2007-2008 GMC Sierra
Equipped with Allison LCT-1000(RPO-MW7)Automatic Transmissions
Customer may comment that the vehicle will not crank or start/will not shift after vehicle has been jump started due to battery run down or after installation of after market equipment.Technicians may find no communication with the TCM and or DTC U101 [my PPE had only a C101,which I know isn't the actual DTC]stored in other modules.
A few TCM's have been returned from the field for analysis because of the above symptoms.The field returned TCM's were analyzed and found to have two battery ground nodes inside the TCM damaged by excessive electrical current passing through the heatsink of the TCM.The nodes affected described as wire bonds are wire tied to pins 9 and 69[battery ground pins] of the TCM.
The TCM is manufactured so that the heatsink of the TCM is isolated from all vehicle electrical systems including vehicle chassis ground.Do not ground welders,battery chargers,electrostatic painters or any other equipment to the heatsink.Disconnect the 80 way connector from the TCM when electrically welding etc. to the vehicle.
To avoid damaging the TCM in this manner,NEVER ALLOW the following:
1. Battery positive wires to touch the heatsink of the TCM[e.g.When jump starting vehicle]
2. Positive battery power chassis harness wire to pin 10 and pin 70 of the TCM to be wired without fuse protection of 10-15 amps.
3. Physical contact between heatsink and vehicle chassis or other ground circuit points.
4. Electrical grounding of devices such as arc welders,battery chargers,and electrostatic painters,or jumper cables to the TCM heatsink.


Recommendations/Instructions: Take the following steps to check for damaged ground wire bondsif the symptoms for a concern are ''No Engine Crank'' and/or ''No Communications'' with Tech II.
1.Switch ignition key off.
2. Disconnect the TCM electrical connector and remove TCM from the vehicle.
3. Test for continuity between pins 9 and 69 at the TCM.If continuity exists between pins 9 and 69,then refer to steps in eSI for ''NO Engine Crank'' and/or ''No Communications''

If the circuit between pins 9 and 69 have no continuity,then the TCM has been damaged/shorted from some sort of external source shorting to the heatsink of the TCM.

1. Inspect for the source that shorted the TCM heatsink.
2. Eliminate or repair the source or condition that caused the damage.
3. Replace damaged TCM after the condition that caused the TCM damage has been corrected.

NOTE: Visual surface pits and carbon deposits are typically found on the TCM heatsink when high energy arcs are generated by shorts between the heatsink and battery power.
 

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Yeah I would like to know that as well
 

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Lbz tcm problem?

Hey y'all, I'm new here so if this has already been answered take it easy on me!
I've got an 07 (Classic) LBZ, this issue has been going on for several months, first off my ABS, Parking Brake light, and "SERVICE BRAKE SYSTEM" lights have all been coming up and it is driving me crazy, and on top of all of this, I can drive my truck for 7 hours straight, and when I get in to start it after that, my truck will barely turn over and fire, (if it does at all) anyhow, does this sound like the TCM to anyone? If not does anyone have a clue as to what it might be?
- Michael

2007 Chevrolet 3/4 Ton LT
LBZ / Allison
5" Straight Pipe
Edge Evo (CTS)
 

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Didn't look at date. Yes they have to be reprogrammed to your VIN. Sounds like a loose connection somewhere. Test your batteries for load 1 at a time. Check starter wires, I know it's tough to reach. This is probably not a ECM problem because it will start. When I turned on the ignition, mine showed all the lights but when I tried to start it would act like a dead battery.
 
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Discussion Starter #7
Sounds like weak batteries-- when load testing, be sure to isolate one battery, as they are connected together to make one BIG battery.

Note: The ONLY reason vehicles have batteries--- is just to start the engine-! Batteries are heavy, dangerous, hazardous, and require maintenance.
 

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Brand new. My truck sat for a year. Just put in a new motor and they believe it arced across it. Batteries keep the computers communicating. A Chevy batteries will run down in about 2 weeks due to the draw. Did you know home computers draw amperage even when shut off?
 

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My ECM and TCM were both burnt. Supposedly due to letting it sit for a long period without enough voltage.
 
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