[Hannah865]

2013 Chevy Silverado 3500 dually
6.6 lml
Allison 1000 auto trans
Everything is stock except having a CM flatbed installed 1½ years ago.

I was driving Saturday, kinda crappy rainy day, and suddenly my truck feels like it lost power. My first thought was fuel filter because I know I'm over due to change it. Check engine light comes on so I pull off and scan it. I notice that it's not accelerating the same, then when I went to put it in park in clunked HARD. Scanner pulled a generic U0101 code-TCM lost communication. Cleared codes, start the truck up and notice no indicator line on the PRNDL. Shift into reverse, clunks hard, shift into drive and it clunks hard again. Start limping it the 30 miles home and am limited to 3rd gear (I think, maybe 2nd). Truck starts dinging and ABS and Brake light come on. Scanned again when I got home, still U0101 code. Cleared it, check engine light goes out, but no other change. Said screw it and went to bed. Next morning, start the truck up, no codes, no lights. Drive it down the road, shift indicator light disappears, abs and brake light come back on. Drove it in Limp mode to the parts store for them to check batteries and scan it for me. Had one weak battery, decided to go ahead and replace both. Their scanner showed the same U0101 code and a C0055 code (ABS /Rear speed sensor.) Noticed limping back home that the speedometer was being erratic and would jump or drop 5-10mph with no change in acceleration. Changed the VSS on the transfer case, cleaned the ground on the frame under the driver's side, disconnected and cleaned wiring harnesses, checked all fuses, pulled TCM and checked harness for power, checked as best I could for loose or damaged wiring. Everything checks out, but it's still doing the same thing. I disconnected the batteries for 24 hours and tried the TCM reset procedure, still nothing. Check engine light will go out, then come back on as soon as you drive or idle for a few minutes. I'm at a loss, please help! I'm hoping it's not the TCM, because nobody has one.

 

[Piper One]

Had that U0101 code once, was TCM. Something inside started to fail as soon as it got warm under the hood. The clunking is it being in limp mode and defaulting to a high line pressure.

The erratic nature of the speedo makes me think it still might be a wiring issue though.

 

[Ron Nielson]

Some base info to add to your collection is attached. If yours was a 2011, Id jump to relace your TCM, but the 13's were not as problematic as the 11's. But it could be TCM. It could be your EBCM also, and wiring problems are yet to be discovered.

 

[Hannah865]

Some base info to add to your collection is attached. If yours was a 2011, Id jump to relace your TCM, but the 13's were not as problematic as the 11's. But it could be TCM. It could be your EBCM also, and wiring problems are yet to be discovered.

I've put a test light on the harness to the TCM and it's getting all the time power at pins 10 and 70, and power with the switch on at pin 2, but pin 63 is iffy. I don't have a multimeter to check continuity. If I'm not getting ignition power to pin 63, what could be the source?

 

[Hannah865]

Some base info to add to your collection is attached. If yours was a 2011, Id jump to relace your TCM, but the 13's were not as problematic as the 11's. But it could be TCM. It could be your EBCM also, and wiring problems are yet to be discovered.

Thanks for your help and the diagnostics info!

Thought I'd also mention that my truck has stupid high engine hours.... Right at 9,000 for roughly 200,000 miles. A company I spoke to a rep that sells programmed TCM's and he mentioned that it most likely was the TCM due to high engine hours and the fact that the truck is limited to 3rd. Any thoughts?

 

[Anacharssis]

2013 Chevy Silverado 3500 dually
6.6 lml
Allison 1000 auto trans
Everything is stock except having a CM flatbed installed 1½ years ago.

I was driving Saturday, kinda crappy rainy day, and suddenly my truck feels like it lost power. My first thought was fuel filter because I know I'm over due to change it. Check engine light comes on so I pull off and scan it. I notice that it's not accelerating the same, then when I went to put it in park in clunked HARD. Scanner pulled a generic U0101 code-TCM lost communication. Cleared codes, start the truck up and notice no indicator line on the PRNDL. Shift into reverse, clunks hard, shift into drive and it clunks hard again. Start limping it the 30 miles home and am limited to 3rd gear (I think, maybe 2nd). Truck starts dinging and ABS and Brake light come on. Scanned again when I got home, still U0101 code. Cleared it, check engine light goes out, but no other change. Said screw it and went to bed. Next morning, start the truck up, no codes, no lights. Drive it down the road, shift indicator light disappears, abs and brake light come back on. Drove it in Limp mode to the parts store for them to check batteries and scan it for me. Had one weak battery, decided to go ahead and replace both. Their scanner showed the same U0101 code and a C0055 code (ABS /Rear speed sensor.) Noticed limping back home that the speedometer was being erratic and would jump or drop 5-10mph with no change in acceleration. Changed the VSS on the transfer case, cleaned the ground on the frame under the driver's side, disconnected and cleaned wiring harnesses, checked all fuses, pulled TCM and checked harness for power, checked as best I could for loose or damaged wiring. Everything checks out, but it's still doing the same thing. I disconnected the batteries for 24 hours and tried the TCM reset procedure, still nothing. Check engine light will go out, then come back on as soon as you drive or idle for a few minutes. I'm at a loss, please help! I'm hoping it's not the TCM, because nobody has one.

Check all your fuses with a multimeter. Look for corrosion. You can download a free pdf of your trucks manual online. If that’s not it, try the replacing the ABS module.

 

[Ron Nielson]

power with the switch on at pin 2, but pin 63 is iffy. I don't have a multimeter to check continuity. If I'm not getting ignition power to pin 63, what could be the source?

Did you notice that the common connection is the IGN 1 voltage (from the IGN 1 fuse)? And to be clear, you don't want to just test for continuity, although as a first step this is fine, what you want is to make sure that the circuit carries sufficient amp load so that it functions correctly. You are probably aware that the wiring is made of many strands of wiring and if even 1 or 2 strands have continuity, you will get voltage, but the circuit will not carry the load needed. Also, I don't know what you mean by "pin 63 is iffy" In any case, made sure the IGN 1 fuse is good and makes a good connection to the fusebox itself. Slide the fuse in and out a few times to see if that makes any difference. And remember that every circuit needs a good ground so be sure to verify the grounds.

The connector view also makes reference to which circuit is involved. Look for that circuit number 2139 in the manual to see what it is.

When dealing with these problems, it is extremely difficult to troubleshoot problems without a good scan tool (not a code reader) and/or scope to see what is actually happening. And those are pretty expensive.