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TCM and EBCM codes, 8.1L 2500HD 2004

TCM and EBCM codes, 8.1L 2500HD 2004

Postby IamNotaMango [OP] » Mar 20 2017, 7:09pm

Hi Guys,

So I just bought a super cheap 2 owner 2004 2500HD 8.lL leather/ bose/ etc. Knew it would be some work to get back into shape. It's sound mechanically (very little rust too) but the last owner trashed it pretty good. Here's the top 2 issues I haven't been able to solve after 3 days of working on it:

1) The dash, including info display usually don't work on startup, at all. But sometimes they do work. When not working the speedo and others read much lower than they should - so 60 reads as 40, half reads as 1/4 and so on. Frustrating, no real rhyme or reason for when the dash works and when it doesn't.

2) The engine light started coming on about 5 secs after startup. It is throwing codes P0700 (general trans), C0035+C0055 (wheel sensors), C0245 (EBCM), C0201 (master cyl sensor), and P1779.

The truck has the Allison 1000. The ECM/TCM is 1 box bolted to the rad. Of interest I couldn't find a fuel filter anywhere so it may be a late 2004 or early 2005 with the integrated fuel pump/ filter, or its hiding somewhere real special on these 8.1s.

The truck drives and shifts. There are no other error lights or codes. This is what I've done to try fixing:
- Fixed all grounds I could find (3 were broken), including 2 under the hood and the ground under the driver seat on frame.
- Replaced 5 blown fuses, I checked fuses again yesterday and couldn't find any blown, but codes all come back after clearing.
- Removed and cleaned the corroded posts and connectors on battery
- I've also done some general maintenance like oil change, new serp belt. Tranny fluid is fine and tranny shifts well.

The owner said he knew nothing of mechanics and had "shorted something out" a few times (I could tell). Any known issues? I read much of these errors are through the TCM, am thinking of finding a salvaged one somewhere.

Here's some pics.
https://drive.google.com/open?id=0B1KjqiMRYtAhdGdqMkNCb3otS3M
Original Poster
IamNotaMango
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Newbie
Posts: 3
Topics: 1
Joined: Mar 20 2017, 6:37pm
Location: BC, Canada
Year: 2004
Make/Model: GMC Sierra
Extra Info: 2500HD 8.1L Crew 4x4
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Re: TCM and EBCM codes, 8.1L 2500HD 2004

Postby IamNotaMango [OP] » Mar 22 2017, 6:31am

Hi it is solved, loose pin on the TCM/PCM connector and now the dash issue and all those codes have cleared up. Crazy how much trouble 1 pin can cause!
Original Poster
IamNotaMango
Newbie
Newbie
Posts: 3
Topics: 1
Joined: Mar 20 2017, 6:37pm
Location: BC, Canada
Year: 2004
Make/Model: GMC Sierra
Extra Info: 2500HD 8.1L Crew 4x4
Group Membership:
Registered users

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