Hi im new to this forum and been reading a lot about trucks like mine and need help . I have a similar problem 1998 LMTV m1078 3116 pulling a code d1-6600 d2-4212 d3-6927 I found wires that where rubbing against steering wheel bar. I did try to fix that issue But still can’t get my truck to drive won’t go into gear no communication to Transmission so I thought I did a poorly job crimping my wires and tape. Would that problem burn my ECU ? Also noticed that my k34 relay gets to hot by touching it, ECU was on the worm end by touching it is that normal? Also I changed my A solenoid and internal wire harness in transmission , I check my grounds to Frame and polarity protection device I had 12v and 24v and I have 12v and 24v at PDP. now is it normal for duel voltage regular light jump from 12v to 24v back and forth? Thanks
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1998 LMTV m1078 3116 pulling a code d1-6600 d2-4212 d3-6927
- Thread starter Vovka
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Based on those codes the TCU is bad.
The downfall of the 3116 FMTV's. The engine might be mechanical but doesn't do any good when the TCU fails. This was not uncommon.
The downfall of the 3116 FMTV's. The engine might be mechanical but doesn't do any good when the TCU fails. This was not uncommon.
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Is your display have blue green digits or red digits?
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Page 54
It does suggest testing for shorts to battery positive on the solenoids switch terminals. But otherwise this generally means an internal TCU fault.
Can't find reference to a 4212 code.
6600 usually means the TCU isn't getting signal from the engine computer. Is this a 3126b truck?
coachgeo
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with a 1998 LMTV w/wtech II would that not make a 3116 truck?
It is 3116 and w/wtech III as I was told when I ship out the TCU for check up, they said i needed a solenoid replacement and internal wire harness so I got that and replaced it so still nothing. I did that repair last summer now I’m back at it.
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Suggest you go over the harness extremely thoroughly from the WTEC III controller to the transmission looking for more wire issues. Especially where the harness flexes when the cab rotates. The controller verifies that the two wire solenoid circuits are: 1. Not shorted to ground 2. Not shorted to battery 3. The correct ohm value. If these self tests fail, you get the error codes you see. The manuals gives you the ohm values for the solenoid circuits at both the WTEC controller and the transmission connectors.
Ronmar
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Have you ever seen this truck operate correctly? With a 3116 engine and properly programmed wtec2 or 3, you should never see code 66. That indicates loss of serial comms to the Engine Control Unit(expecting to see throttle position data from engine computer), which this truck never had…
code 42-12 indicates a short to battery on solenoid circuit A
69-27 is not listed in the allison troubleshooting manual, but allison is pretty logical in the way it lays these out. 69 indicates an ECU fault. This manual uses the acronym ECU to mean Electronic Control Unit(not engine control unit), instead of TCU for trans control unit. Subcode 26 is a ECU open driver for the N solenoid(all the previous subcodes are also open solenoid drivers). Subcode 32 is ECU, SPI communications link fault. Serial Peripheral Interface — Connection between ECU(TCU) and integral shift selector. So Subcode 27 is probably some other driver, or comms related fault.
The transmission, wiring harness and TCU are all matched by versions as they made changes thru the different production years. Mis-match one of these 3 and they won’t work correctly. Also, the TCU must be programmed for the particular application, in this case a mechanical 3116 with a standalone throttle position sensor, and not a 3126 with ECU and TPS data over serial connection. That code 66 tells me either this TCU is really broke, wiped or mis-programmed, or it was swapped with an incorrect version for this truck. Thats why I asked if you have ever seen it work properly? The other codes could easilly be a result of the mis-matched TCU not very happy with an incompatible environment…
code 42-12 indicates a short to battery on solenoid circuit A
69-27 is not listed in the allison troubleshooting manual, but allison is pretty logical in the way it lays these out. 69 indicates an ECU fault. This manual uses the acronym ECU to mean Electronic Control Unit(not engine control unit), instead of TCU for trans control unit. Subcode 26 is a ECU open driver for the N solenoid(all the previous subcodes are also open solenoid drivers). Subcode 32 is ECU, SPI communications link fault. Serial Peripheral Interface — Connection between ECU(TCU) and integral shift selector. So Subcode 27 is probably some other driver, or comms related fault.
The transmission, wiring harness and TCU are all matched by versions as they made changes thru the different production years. Mis-match one of these 3 and they won’t work correctly. Also, the TCU must be programmed for the particular application, in this case a mechanical 3116 with a standalone throttle position sensor, and not a 3126 with ECU and TPS data over serial connection. That code 66 tells me either this TCU is really broke, wiped or mis-programmed, or it was swapped with an incorrect version for this truck. Thats why I asked if you have ever seen it work properly? The other codes could easilly be a result of the mis-matched TCU not very happy with an incompatible environment…
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The lmtv gen3 tcms are autodetect programmed the same programmed tcm can do a 3116 tps or 3126 engine computer signal. I have good tested ones on hand.
Ronmar
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Ok, then it sounds like a harness mismatch or issue telling the TCU that it is in a different environment…
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What if the tcm isnt seeing the tps
Ronmar
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Well if it is in the mode of looking for a standalone TPS I would suspect it would give some form of TPS fault like a 21-12 or 21-23 for failed low or high as it would report a TPS voltage outside the idle and full throttle positions stored in memeory…
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Either bad tcm or wiring issue then. You can see on his label pic under throttle it says autodetect. The tcm label pictured looks correct. The newer trans to cab harnesses have colored wires in the bundle. The older ones that the insulation cracks and you get shorts are usually all white wires.
So yes bought my truck off an auction I drove truck 100 miles to my house sounded like it was in limp mode, because truck shifted up to 5th gear I saw it on the pad and I was driving 20 mph. When I was driving I heard at the PDP relays where clicking as I understand that was the steering wheel bar making contact shorting out something. This is the second year truck sitting not driving.
Sorry don’t understand TPS is ? and TCM is transmission control module?
Can I ship mine to test TCM or if so how can I check if current TCM is good ? How can I contact you to buy one ?
Ronmar
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TPS = Throttle Position Sensor. On the 3116 it is on the drivers side of The cylinder head above the primary fuel filter.
Is there a way to test that tps?