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M1089AO with transmission issue.

Bmbush

New member
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Location
Lansing, NC
Good evening,

I have a 94 M1089 we recently bought and are bringing back to life. Please I know there is a post on this code already but let me explain our situation and maybe someone can help me out cause we are not driving anywhere fast at the moment. This truck is 25 years old and only had 1200 miles on it when we bought it.
Not uncommon I know but she's all original no mvo's.

Two weeks ago I went out for a trip to the parts store and we lost our injector cups in the head. In the course of turning around and getting home roughly 5 miles I lost about 50 gallons of diesel out of the coolant overflow tank. I got the truck in front of the shop and shut down. I started it again to position in front of the shop and lost response of the transmission pad. At the moment I didn't care, I moved to address the major issue. Head came off got new cups and everything else addressed in regards to the top end of the motor. It's back together now, running great with no issue. I put the truck in drive, start to move, once I'm moving the left number on the touchpad disappears and I'm stuck in second gear. Code on the transmission is 2511. The first code we got was for the proximity sensor on the top of the bellhousing. We pulled that out and replaced it yesterday. It was destroyed and to our pleasant surprise the tach started working. But same issue remains, stuck in second gear and we have no speedometer which has worked previously. Also noticed at this point we have no reserve light. No power to the light, light worked before this issue. It is working when power is applied separate of the system, and the fuse is good.

Today I pulled the output speed sensor in regards to our current and only code 2511. Ohms checked at 289 out of the truck which should be acceptable from what we've read. Trucks back together and we still have the issue.

I've forgot to mention we started with the ECU. I was in the dash previously and though it might be a ground issue or something I did. I pulled the entire controller apart and to our not so much of a surprise it was full of water. Cleaned and inspected everything, nothing was obviously damaged and it's worked for our 500+ miles of driving, so I reassembled and reinstalled. It's working fine like before.

I know reading this the obvious thing to jump to is the water in the ECU. I must mention we have gone thru this truck top to bottom and done alot of work. Money is tight now and while if replacing the ECU fixes the issues that's great but I can't throw away money to just start replacing stuff that isn't the issue. I'm looking for suggestions on sensors or testing the ECU or whatever anyone who has experience in this situation could suggest.

Sorry for the long post just trying to give the back story. Any help would be greatly appreciated.
Thanks
 

Coffey1

Well-known member
Steel Soldiers Supporter
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Location
Gray Court SC
I know on my 1089 when the alternator wasn't charging the batteries they got so low it was locked in 2nd.

As soon as I repaired alternator and put fresh batteries in all was good .
 

Bmbush

New member
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0
1
Location
Lansing, NC
Mine is a 95 with 8k on it
The truck sat when the head was off. Our batteries were dead when we went to refire. We know the alternator is charging and working, literally just checked it again. We charged all 4 individually and they all recovered.

We got this thing with just over 1200 miles and we got lucky to get just about everything with it.
 

NDT

Well-known member
Steel Soldiers Supporter
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Location
Camp Wood/LC, TX
Lots of us have had great luck with transmissioninstruments.com. The guy will diagnose for free and not charge you if your controller is good, which in your case is very unlikely.
 

Bmbush

New member
6
0
1
Location
Lansing, NC
Lots of us have had great luck with transmissioninstruments.com. The guy will diagnose for free and not charge you if your controller is good, which in your case is very unlikely.
Awesome thanks, I ordered new batteries today. If that doesn't fix it, that will definitely be my next step. Found a bad battery last night, after the 3rd check lol. Thanks again
 

Andyrv6av8r

Well-known member
Steel Soldiers Supporter
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Location
Spartanburg,SC
I had an issue very similar to yours with my 1078. All was fine then one day it was stuck in 2nd gear. I too replaced a mangled speed sensor to no avail. And in the end the problem was my transmission fluid level was low . And the speed sensor wasn't even needed since the transmission works fine whether it's plugged up or not.

Read my thread:

 

Bmbush

New member
6
0
1
Location
Lansing, NC
I had an issue very similar to yours with my 1078. All was fine then one day it was stuck in 2nd gear. I too replaced a mangled speed sensor to no avail. And in the end the problem was my transmission fluid level was low . And the speed sensor wasn't even needed since the transmission works fine whether it's plugged up or not.

Read my thread:

We've tried the plug and unplug sensor diagnostic earlier this week. I got on here and read that very post and started with that after the speed sensor. Sorry I forget to mention that, it's hard to remember to type everything tried. The transmission has new filters and fluid too. Fluid level is good as well. Thanks for your reply and original post it was helpful!
 
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