Hey Guys! I have a bit of a problem. My trans has been acting up with shift points, slamming into gears, up shifting and down shifting right after the other. Check engine light came on last night and I pulled up codes P0700, U0073, U0101 and U0105. Is this a TCM or ECM problem? I checked all my fuses and cant find any problem. I also checked the wiring connected to the ECM and TCM and found no chafing or damaged wires, can anyone help!? :confused:

P0700 means that you have trans troubles:

Code: P0700
Modules: ECM, TCM
Description: Transmission Control Module (TCM) Requested MIL Illumination

You need to have the codes read with a scanner that will pull TCM codes. You will find additional codes there to help narrow it down. A call to Mike L. may be in order also, since I see it is his work.

Moved to Allison Aftermarket.

I already talked to him and recomended a TCM change to eliminate that part of the problem if it exists. This is clearly a comunication problem within the TCM, ECM, and trans. Could be wiring or bad ground.

Thanks Guys, I'm currently checking into it and I'll get back with the results.

Update? Did you fix the problem and if so what was the fix. I am having a similar problem as well as a few others.

No, I have not fixed the problem. The dealer thought that it was from some loose wireing or chaffing but they couldn't find the problem. They said that the only thing to do next is replace the TCM and go from there. The part is on order and it should be in next week. I'll give update after the part gets installed and tested.

Ok!, the TCM was not the problem. I still have the codes P0700, P0101, P0105 & U0073. The dealer thinks it might be the ECM and they want to change that and see if that works. I'll give an update when that happens:banghead:

Dying to hear the results. I too have the same issue going on.

Ok, the dealer couldn't find the problem so I went to a friend that is a former lead mechanic for GM and he wanted me to take off my plug and play and see what happens. I have been driving with out the chip for about 3 days now and no P0700, P0101 or P0105 but I still have the U0073 with a little hard sifts at gear 3 and 5 but no more sticking gears. I guess my chip went bad. My friend will look into the U0073 and I'll give update on that.:confused:

UPDATE! The chip was not the problem. The codes P0700, P0101, P0105 and U0073 came back with the gears sticking and slamming. It would first upshift and downshift a couple of times for several miles and then it would just stick inthe gears as if it was in tow mode. I would have to ride the gears intill it shift itself and it would shift hard. Has anyone had the same problem or same codes. Need Help!!:eek: This is going on way too long. The dealer is no help. Thanks

I already talked to him and recomended a TCM change to eliminate that part of the problem if it exists. This is clearly a comunication problem within the TCM, ECM, and trans. Could be wiring or bad ground.


Mike: I have noticed a good number of members with this problem or something very similar. Where would the bad ground be located? I had all my solenoids replaced and a new wiring harness put in back in December and still have the same problems.

Still haven't fixed the problem. Could this be a bad Valve Body? :mad::confused:

Still haven't fixed the problem. Could this be a bad Valve Body? :mad::confused:

You never tried an ECM?

I have a customer's truck with a similar problem and was thinking ECM. Hard to diagnose for sure.

I replaced the ECM and TCM but did not fix the problem. Wires were checked and they could not find any problems or bad connections.

subscribing

I'm interested too...no real shift issues, but throwing P0700 code.

I have similar issues with my truck since I bought it. I have since put in a Mike L tranny and SoCal diesel reprogrammed TCM. Same issue exists in a hard 2-3 shift with any modest acceleration or what feels like two quick shifts when I'm light on the throttle. I think the issue is not tranny or TCM related but am unsure where to check next. Speed sensors, wiring harness, ECM? I'm running out of money chasing this gremlin!

After I put in the SoCal TCM last Wednesday, I immediately got trouble codes even prior to turning on the key, much less starting and driving the vehicle. They were dealing with solenoids A and B. I looked up info on those and it doesn't appear they would have anything to do with my shifting problem.

My truck has aprox. the same problem since it was new but only in the cold weather 5*F or lower and its not consistant once you key off then back on the CEL comes on with a U0100 TCM lost comm. with ECM/PCM. Once you clear the code it will shift normal.