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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29427
Experience:  GM Grand Master Technician 2007. 14 years experience.
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Need diagnostics 09 duramax with trouble codes p 08 80

Customer Question

Need diagnostics for a 09 duramax with trouble codes p 08 80 and u0101
Submitted: 1 year ago.
Category: Chevy
Expert:  GM Tech (Cam) replied 1 year ago.
hi there, I am Cam. Sorry for the delay, are you still needing assistance?
Customer: replied 1 year ago.
Yes I am
Expert:  GM Tech (Cam) replied 1 year ago.
OK, found a bulletin about that combination of codes and it refers to issues with the belt. While I get that bulletin for you, can you tell me if you have an aftermarket belt on the engine or anything added to the system like a PTO or something?
Expert:  GM Tech (Cam) replied 1 year ago.
Attached is the bulletin and a picture with the ground location for G102, which is lower left of the engine block.
Customer: replied 1 year ago.
It has two alternators and just a regular Belt from the parts store
Customer: replied 1 year ago.
It doesn't have any other after market parts
Expert:  GM Tech (Cam) replied 1 year ago.
OK, that may be it. If you look in the bulletin, aftermarket belts, meaning belts sourced from non GM dealers can generate the static electricity and cause this. I suggest before we do anything else that you follow the steps of the bulletin closely and see if that resolves your issue. If not then we may be looking at a transmission module issue, but with the higher charging current and such, I have a good feeling this will correct the issue.
Customer: replied 1 year ago.
OK I preformed the steps in the bulletin an it did nothin truck is still the same but I got another code that came up p0700 ?
Expert:  GM Tech (Cam) replied 1 year ago.
P0700 is just a code that the Transmission module is requesting the check engine light. You put a GM belt in and cleared the codes as well?
Expert:  GM Tech (Cam) replied 1 year ago.
yrAnd did both codes return or just one of the original 2?
Customer: replied 1 year ago.
Yes sir they both came back after the belt cleaning ground cable an have the tcm moved
Expert:  GM Tech (Cam) replied 1 year ago.
Ok, let me dig a bit further. Please stand by.
Customer: replied 1 year ago.
K thanx
Expert:  GM Tech (Cam) replied 1 year ago.
OK so basically we are down to this, check the wiring to the TCM, make sure it gets power with the key on. If so, and if the wiring, connector, grounds are good, it means your transmission module is bad. Its not a plug and play unit, rather it needs to be programmed and setup, then a learn done on your transmission to the module for the clutch fill capacities, which is done also with the scanner after the programming. Here is the bit from the manual. Circuit/System VerificationEngine running, accessories OFF, measure and record the battery voltage at the battery terminals. The reading should be between 12.6 and 15 V. If not the expected value, refer to Battery Charging. Observe the scan tool TCM ignition voltage parameter. The reading should be between 12.6 and 15 V. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data. Circuit/System TestingNote: You must perform the Circuit/System Verification first. Ignition OFF, and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Disconnect the harness connector at the TCM. Test for less than 3 ohms between ground circuit terminal 9 and battery ground and between ground circuit terminal 69 and battery ground. If greater than the specified range, repair the affected ground circuit. Verify that a test lamp illuminates between the battery B+ circuits terminal 10 and ground and terminal 70 and ground. If the test lamp does not illuminate, repair the affected B+ circuit. If circuits test normal, replace the TCM.
Customer: replied 1 year ago.
The ohm meter falls down to 0.2 ohms on are ground circuits an b+ circuits to ground light the test light
Expert:  GM Tech (Cam) replied 1 year ago.
OK, then its looking like a module issue. One last thing to try, take a small wire, attach it to the heat sink pins and ground it. See if that changes anything.
Customer: replied 1 year ago.
Grounded heat sink pin on tcm an still no change looks like the tcm
Expert:  GM Tech (Cam) replied 1 year ago.
I agree. but I will mention this one more time just because its that important, make sure there are no wiring issue to the TCM, No corrosion in the connector and the pin fits are all good otherwise we are going to change this TCM for no reason. That being said, I have seen and replaced a handful of TCM's now so they are somewhat common.

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