I am a newby to the forum, proud owner a 2009 GMC LMM for the last 11 years. I do oil changes, fuel filter servicing, glow plug replacement, two batteries and the truck was reliable until now. Now at 125K miles, having no-crank starting failure. With key held solid to start, the starter would engage for .5 sec, pause for 1 sec, crank again .5 second, pause for 1 sec, crank .5 pause again. Trying subsequent times, the starter might run 1 full second, the truck would start and run fine, until the intermittent starting failure was solid. The Dealer ripped out an aftermarket a 10 year old VIPER Remote Start system, claiming it was causing the failure. Subsequently, they said I had a bad ECM and they could not source a replacement (GM discontinued the part). A third party replacement/programmed ECM failed after driving <20 miles. Before failing, it exhibited very similar random no crank issue as the original ECM. The problem appears to be a wiring issue (Lost COM with ECM faults), but I have not found a smoking gun: bad fuse or relay, chafed wire, loose ground, broken pin in a plug but visual inspections have detected no defects thus far. I have no tech data on the wiring and hoping to find something to focus the next level of trouble shooting. Any tips are appreciated. Is alldata the right place to look for factory wiring diagrams? I also need a recommendation for someone to bench test the two ECMs, hoping they did not suffer terminal failures. I loved this truck for 10 years, Thanks for any suggestions to help get it running and reliable again. I will list the exact error codes in a subsequent post.
Howdy Yall, looking for recommendations for LMM ECM expertise in the Weatherford Tx/Fort Worth area.
- Thread starter ChasFTW
- Start date
Free wiring diagrams are available here https://www.gmupfitter.com/wp-conte...09_LD_ElectricalPickupsChassisCabs_100813.pdf ALLDATADIY does have wiring diagrams, however, my subscription is to their older system and the wiring diagrams there are not as good as GM's. Don't know about the new system they have. You can get service info direct from GM online either for a short time period or other options.
With electrical problems, ALWAYS fully charge both batteries and see if the problem changes or improves. If the electrical supply is not up to snuff, the balance of problem resolution may be suspect.
With electrical problems, ALWAYS fully charge both batteries and see if the problem changes or improves. If the electrical supply is not up to snuff, the balance of problem resolution may be suspect.
Thanks Ron. The gmupfitter doc is a gold mine of good info. I found the X1 and X2 ECM connector/Pins descriptions so I can start measuring voltages at the ECM, with the idea that perhaps the ECM is loosing power may be the reason it it not talking on the GMLAN. Found several of Ground Points on engine and firewall I can check. I found the (Diesel) under hood fuse box layout, #14 DSL ECM (25A) looks like a good test point. I saw a few wiring diagrams on accessories, but thus far have not seen actual diagrams that would map the fuse to the pins in the ECM, or the circuits back to the Ignition Switch. Across the two ECM plugs, there appear to be multiple Ignition 1 Voltage pins, and one Battery Positive voltage pin, which are all on my list to check next. Re the Battery health, when the first sign of starting failures occurred with the original ECM, I check both batteries with a load cell tester (cables disconnected) for a good thirty seconds and both held up well. Since the truck has been sitting a lot since, I am keeping both batteries up with chargers to ensure they are topped off. When the truck was starting intermittently, charging voltage measured consistently about 14.5 volts at idle. Thanks again for your help.
Some additional info for your GMLAN problem. Remember that any device on the plan can pull down the entire plan. Kind of like those Christmas tree lights where when one bulb goes out, they all go out. With lights, it's easy to see which one is out, with our trucks it takes more effort.
Ron,
thanks for the latest info, it was all good. I expected to be chasing GMLAN wiring, and I may yet need to before all is said and done, but I found ECM, fuse #14 - DSL ECM (25A) does not receive 12volts with any position of the Ignition Switch, initially, about 0.1vdc. Fuse #13, ECM-BATT (10A) was hot continuously, as expected, at 12.4vdc. Fuse #56, ECM-IGN (15A) read the same as #14, about zero. I checked all the fuses for continuity, cleaned the fuse box and repeated the voltage checks. Fuse #13 ECM-BATT was still reading the battery voltage level, 12.3vdc. Both Fuses #14 and #56, read 2.7vdc with the Key switch to RUN and 5.4vdc with Key held to START, odd doubling of voltage. At first I thought the Digital Meter was needing batteries replaced and was loosing accuracy, but it remained consistent between fuses 14 and 56, and 13 was consistently reading Battery voltage. During all of this testing, both Batteries were hooked up and within a few tenths of volts of normal high charge and the ECM was removed from the circuit (both plugs dangling). I ran out of time before being able to fetch ECM and plug it back into the circuit. I know better than make assumptions but I do not expect connecting the ECM to make supply voltages increase, but as voltages are already inconsistent, I am wondering if there is a defective relay upstream affecting the supply voltage or bad Ignition Switch, or wiring in the column grounding out?
This truck went to the local dealer initially, and all they did was remove the 10 year old Viper remote start system. Afterwards, they said I had a bad ECM. I think they should have done simple voltage supply testing but they would not discuss any details of the "work performed", other than to say they cleaned up the splices that enable the VIPER system connections. I have not yet dug into the wires inside the cab, where the two VIPER boxes were ziptied under the dash.
I feel your pain brother. My GMLAN low speed databus issue is back again. More than frustrating after replacing both the BCM and the air bag (SRS) module. The only thing I can add to your issue is to check the engine harness that runs along the back of the engine. That is a known issue for ECM and injector electrical issues. Dean
That is one thing I have noted. Since diesel prices are up I have not been driving the truck as much. I do know that if I let the truck sit for 5 days or more without running the batteries will be very weak. My batteries are 4 years old and even fully charged the truck will turn over and start but even the dash lights will will be dimming when the engine is cranking. Might need to replace both batteries just to make sure but normally with lead acid batteries I normally get at least 5 or 6 years before they start dropping off. Charging wise everything looks good. Dean
Thanks Dean, I will put that on the list of things to inspect. I am still looking for the pin to pin diagram of wiring that feeds the multiple ECM fuses as recent testing at the fuses show low and sometime no voltage feed the 25A circuit to the ECM. Fault code 0100, Lost Communication With ECM/... seems to be a reoccurring theme, back when this started, which could be bad GLAN wiring but could also be the supply voltage is insufficient to power the ECM. The latest clues, at least are pointing in that direction.
Did you reprogram the new ECM for your injectors? That would eliminate at least 8 of those codes you have, maybe more.
Dead/dying batteries will also cause many odd codes to show up, and I see "low voltage" in there, so.....
Dead/dying batteries will also cause many odd codes to show up, and I see "low voltage" in there, so.....
Clear the codes and see what comes back. That list is like pulling a whale into a 4 ft fishing boat.
That list of codes was what appeared immediately after installing the replacement ECU, which was sold as a "stock program" with my VIN the only customization. After the truck started (not the first, second, or third try), I let it warm up for a long while just siting in the driveway, but did not drive it that day. I cleared the initial mess of faults, including the injector faults, Regen fault cleared, and never came back. The single bad Glow Plug remained but I have had that one for years. A week or two later, I was brave enough to drive it but it hard failed on that trip, 5 miles from home, had call AAA. Norther tool had a cheap code reader on sale, and the next time I used it, but it only displays on the hand unit, could not save to phone or pc. On April 14th, the following were the only remaining faults: U0100 ABS Loast Comm with ECM/PCM, C0055 Rear Wheel Speed Sensor Circuit Malfunction, and EBCM O8600, EBCM U8600. Since none of the Fuel Injector faults returned, I wrote that off as new ECM getting powered up for the first time. The one fault that keeps reoccurring is U0100, which left me speculating GMLAN wiring failure or the new ECM is now also Dead, Dying or not getting power. I was hoping to find more info on B1441, but that also happens to be a popular fuel filter PN and that is all the search function returns hits for.
Not sure it that is a fault or just a status.That being the case, you still need to program the injector values to the ecm. It's not QUITE plug and play like thecLB7/LLY would be... They can be copied from the gpcm to the ecm with a tech2 or efilive v2. Like Tom said, that would likely eliminate at least eight of the codes you have.
Sent from my Pixel 5 using Tapatalk
Last edited:
