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Discussion Starter #1
Hello,
My son's 08 G6 will not start or even try to turn over. It shows error on odometer after all needles have swung on the cluster.I searched the forum for solutions and tried some to no avail. Borrowed a diagnostic tool from a friend and it showed the following... lost communication with engine control module/powertrain control module "A". Also want to add that battery shows only 9 volts at terminals + neg. cable is a bit loose connecting to battery. Will a low battery cause this lost communication thing? Or is it likely that it is the battery and something else also. Hope someone can help as he and his wife have a brand new baby and just bought the car 4 or 5 months ago so they would have something dependable. Car only has 46000 miles. Thank you !!
 

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Moderator Member Thingy
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The car won't run on 9 volts. You need to charge your battery (if possible). If that doesn't up the voltage on your battery to 12.8V or more then you need to get a new battery.

Error on the odometer usually means a miscommunication between the PCM (and sometimes BCM). In my case, I had to get a new PCM. Your first order is to get the battery functional though.
 

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Discussion Starter #3
Well, we got a new battery as the old one was shot. However, it did not solve the problem. Still nothing and swinging needles and error on odometer. Advice on next step? New PCM? Grounds seem ok. Tried swapping little modules in fuse box. Tried shifter in park and neutral. Wadda ya guys think?
Thanks.
 

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Since the battery is new and the odo shows error, then your PCM is likely done, It's located in front of the battery box in plain view in the engine compartment, I suppose you can try to:
Disconnect the battery, Unplug all the connectors from the module, and try to clean both the plugs on the wires and the module, once it's all dry, reconnect and then reconnect the battery. if that still doesn't do it then you need a new PCM.

If you get a new one you'll need to have the PCM programmed with the VIN for your vehicle for it to work, and if it's a new unit it may require a CASE relearn in the future.
 

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Discussion Starter #5
Bummer! Ok...forgive my ignorance. How or who do you get to program the PCM and why the vin and all that? And...a CASE relearn? Huh? Please explain.
Thank you.
 

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I believe only the dealer can do all that. not sure if you are within your bumper to bumper warrante or not but might be able to have them cover it.
 

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... neg. cable is a bit loose connecting to battery. Will a low battery cause this lost communication thing?
Not sure exactly what you mean here. All battery cable connections must be corrosion-free & tight. Especially check the battery ground straps. A poor battery connection can cause the described symptoms. If no joy after cleaning & tightening all battery connections, I would consider taking it to a mechanic for a diagnosis. Then maybe you can DIY the repair.
 

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Discussion Starter #9
Will double check a few more grounds. Still don't knoe what a CASE relearn is. Any one want to explain. All the electronic gizmos gives me a headache sometimes. Thanks
 

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crankshaft angle sensor error or something like that, Google it and you might have some alternative solutions before taking it in.
 

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A crank relearn just learns the position of the Crankshaft Position Sensor. It's mainly there to aid the computer in compensating for misfires. Due to the constant changing in timing these cars do they're bound to miss a fire here or there. So when the knock sensor detects a misfire condition, the computer can quickly retard timing or adjust any one of many many things to stop the misfire and keep it running good. You'll know if you need this by the check engine light being it. The engine and car will still run and drive though.

There are a lot of ground points to check, but even if their nice and tight, check for rust or the integrity of the wires themselves. Check all ground and positive connections too, Just make sure plugs are in all the way
 

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Discussion Starter #12
Will do! As for the programming of the PCM if I need one...is it strictly dealership stuff?
Thank you
 

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Which engine is in that vehicle?

If it's the 4cyl Ecotec, problem could be ground 105:


Service Information 2008 Pontiac G6 | G6 (VIN Z) Service Manual | Document ID: 2200174
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#PIC5003: No Crank / No CommWith U2105 U2106 U2108 U2109 (LE5 Only) - keywords 2.4 2.4L communication start - (Oct 15, 2008)


Subject: No Crank/No Comm with U2105 U2106 U2108 U2109 (LE5 Only)


Models: 2008-2009 Chevrolet Malibu

2006-2009 Pontiac G6

2009 Saturn Aura

This PI only applies to vehicles listed with (LE5) Engine only




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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
A condition has been identified that could cause a NO crank/No communication on the LE5-4 cyl engine. This condition has been identified as a loose ground G105 behind the A/C compressor.

Recommendation/Instructions:
Remove the bolt from G105 and clean the engine block surface. You should also make sure the terminal is tight after the bolt is tightened up. There have been reported cases of the bolt bottoming out in the hole and not generating a clamp load on the terminal.

Important: Please reference Document ID: 1986240 for location purposes.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.



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.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION


© 2012 General Motors Corporation. All rights reserved.
 

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This applies only if you have the onstar module:


Service Information 2008 Pontiac G6 | G6 (VIN Z) Service Manual | Document ID: 2324430
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#PIC4677C: No Start No Crank Intermittently / No Communication Over High Speed LAN - keywords connector inop inoperative lamp light loose message on onstar U0121 U0101 U2100 U1040 P0700 P2544 U0073 VCIM warning - (Aug 10, 2009)


Subject: No Start No Crank Intermittently/No communication over High Speed LAN


Models: 2008-2010 Chevrolet Malibu

2006-2010 Pontiac G6

2007-2010 Saturn AURA




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This PI was superseded to update model years. Please discard PIC4677B.


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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
A customer may have a complaint of an intermittent no start, no crank condition, and or SES light on with I/P gauges intermittently inoperative while driving. Any of the following DTCs may be accompanied with this complaint. U0121, U0101, U2100, U104, P0700, P2544, U0073

Recommendation/Instructions:
Before beginning to deep dive into any diagnostics first (If equipped) check the VCIM module (Onstar) connector C3 (Black) to be sure that it has been fully seated. This connector has been increasingly showing up as the root cause for loss of HIGH speed LAN concerns.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.



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.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION


© 2012 General Motors Corporation. All rights reserved.
 

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Discussion Starter #16
greenman,
Thank you for all the info! I'm sorry I have not gotten back to the discussion until now as I work 12 hour shifts Thurs. thru Sunday. I will process all the info you gave me. The engine in the car is a 6 cylinder. Thank you and I'll be back!
Neb
 

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Same Problem

greenman,
Thank you for all the info! I'm sorry I have not gotten back to the discussion until now as I work 12 hour shifts Thurs. thru Sunday. I will process all the info you gave me. The engine in the car is a 6 cylinder. Thank you and I'll be back!
Neb
My 2007 G6 convertible just developed this problem. The car sat in the driveway for the weekend and, come Monday morning, "error" on the odometer and no start. Battery voltage is fine. Did you get your G6 running again? Please report back. Thanks!
 

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Let me begin by saying I'm not very technical, so I hope this makes sense to someone who may have the same problem I had. I have an '09 Pontiac G6, wouldn't start, wouldn't even turn over, error on speedometer, but power windows, headlights, radio, etc., were working and the battery was relatively new so we didn't think that was the problem. Towed to the dealer, they determined it was the PCM--no communication to the engine. They ordered the PCM, replaced it, still no communication with engine. They dug deeper and found the battery cable insulation split and apparently shorted out the PCM. So, now they are replacing the battery cable (hopefully this should do the trick, I'm picking it up in a little while). I would imagine this could have cause an electrical fire, very thankful that wasn't the case!
 

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I wanted to revise my post, after getting the car back. This is what the paperwork said: No communication with ECM, had no power. Ground to ECM. Replaced ABD program new ECM. During repair found neg battery cable fraying and cracking, replaced negative cable. They said the frayed battery cable caused the ECM to fry--does that make sense? Someone at work is insinuating I was "taken"--even tho the dealer didn't charge me for the ECM (he wanted me to go to his mechanic). Would appreciate any comments.
 

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The battery cable was the no start. Just be glad you were not charged for The ECM.
I would call it poor diagnostic, especially for a dealer.
 
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