Engine/Transmission (1998.5 - 2002) Anyone heard of this?

[AutoRepair]

I have have a 99 cummins in the shop with the TCC erratic lockup problem I have seen many times, but this is a new one. Most of the other TCC issues I have had in the past have ussually been TPS failure, or leaky alternator diodes. This one has the fuel metering solinoid pattern leaking into the 5v ref. signal on the cummins ECM. Since the TPS uses the 5v ref, the TPS signal is screwed up and unlocking the TCC. I'm afraid it will need a new Injector pump to fix the problem, but thought I'd see if any of you guys had run into this before first. The pump on the truck is a factory Bosch reman that's a couple of years old. Any help would be great, thx.

 

[Nyoest]

I cannot help however I am curious how you diagnosed it?

 

[cerberusiam]

Remove the charge wire and the battery ground wire form the harness and then check your readings again. The noise your getting is typical of the bleed over form ther alternator as it ages and the wire shielding deteriorates.



That truck has an APPS not just the simple TPS, the reference signals are used by the ECU to determine and set fueling. If there was enough problems with the signal you would have CEL's and codes. The TC unlock is purely under the control of the PCM, but, the signal wash you are seeing is getting fed to the PCM. That is generalyl what is causing the intermittent problem.



Grounds, both on the battery and chassis are a biggy to check. Batteries in good shape and able to hold a load test also. Still, the best solution seems to be getting rid of the noise source to solve the intermittent stuff.



If that doesn't completely cure it, put a triple disk TC in it. Always works doing that. :-laf

 

[JLandry]

Also, put a NEW (not rebuilt) alternator on it to help eliminate electrical noise. You can buy new alternators on eBay for about $100.



John L.

 

[John - K5AWO]

I installed the DTT noise filter and the problem disappeared.

I also have a triple disc TC and the heavier valve body to make darn sure it locks in solid. So solid, it feels like a stick shift and a heavy clutch foot.

 

[AutoRepair]

Thanks for the replys guys, Already unplugged the alt. before I found out the Fuel metering solinoid was the sourse of the "noise". I found the problem by using a lab scope to watch the APPS signal to the ECM. I have seen quite a few of these signals and knew right away it wasn't normal. I took a few more patterns with the scope and found out the strange noise was in all of the 5V sensors circuit. When I first found the glitch in the signal, I knew it was caused by a solinoid because I've seen solinoid patterns on the lab scope. It did take me a while to figure out it was caused by the fuel metering solinoid because I didn't know what electronics were in the inj. pump. Once I found out the inj. pump had a solinoid in it, I put the fuel metering soliniod pattern and the APPS pattern up on the scope and they matched perfectly. So I know where the glitch is coming from, I just don't know if the signal cross is in the pump or the ECM... I don't feel like guessing if you know what I mean.



John,

The DTT Noise filter, is it installed on the 12V side of the motor, or in the APPS circuit? It sounds like it may do the trick if it can clean up the 5V Ref.



Thanks again for the help guys, GREAT site.