Tranny Trouble Codes

[lmholmes11]

Hi all, last night my truck threw 2 codes. 1- p0700 ( indicates there is a problem with the TCM/Tranny) and a P 1781 (Failure to communicate with the ECM at start up).

What could cause these trouble codes? Is the p0700 due to the p1781?

Before the light came on there was no slippage in the tranny, and I can't remember if both codes activated on start up or shortly after start up. I am going to say it was on start up. Thanks guys.

[lmholmes11]

Does anyone have any info on this?

[Mark Rinker]

Have you searched all Duramax forums on these codes yet? Tranny codes aren't real common around here, so unless you find information by searching on them, its unlikely you'll get any other firsthand experience.

Are you running any programmer or extra power? What was the truck doing before the codes were set? Temperatures?

How is the driveability right now? Normal or limped?

[lmholmes11]

Driveability is normal, temps are normal, everything is normal. I will try to do a search again, but all i can find is that the code signals the SES to illuminate.

[More Power]

Hi all, last night my truck threw 2 codes. 1- p0700 ( indicates there is a problem with the TCM/Tranny) and a P 1781 (Failure to communicate with the ECM at start up).

What could cause these trouble codes? Is the p0700 due to the p1781?

Before the light came on there was no slippage in the tranny, and I can't remember if both codes activated on start up or shortly after start up. I am going to say it was on start up. Thanks guys.

A P0700 is sort of a generic Allison trouble code. I saw this one once after installing an Allison without any ATF, filling it the requisite amount, then starting the engine. It took a while to circulate the fluid, and it set a P0700. Once running the engine for a short while, topping off the ATF, and re-setting the codes, it didn't return. So, a P0700 can set by itself and it can accompany other codes.

What I do is reset the codes anytime they first appear, then see if they return. Many times they won't. If they do, then it may be a real problem, and further investigation is called for.

Do you have any special ECM/TCM programming? Any performance products that affect the electronics? How many miles since the Allison was serviced?

Jim

[Mark Rinker]

How old are your batteries?


Did you have a severe cold startup, where the batteries may have been momentarily taxed to the point of a severe voltage drop? That may have been enough for the code(s) you have...

[lmholmes11]

Yes, a lot of recent cold start ups. I do need to replace my batts, as they have been dead the next morning after running normally around town. I will replace batts and report back.