It's been awile since I've been on DTR and I'm glad to be back. My ex g/f made me get rid of my 1st gen duelly and i miss the old girl... (the TRUCK... Not the EX)
But I"m back and glad to have another Ram/Cummins.. I'm having a few issues with it though. The main two issues are charging and transmission shifting. I'm guessing maybe a common link between the two and I'm hoping a ground issue.
Here's the situation.... I just bought a 99 2500 24valve clubcab shortbox with 167,ooo miles from the original owner. He was having charging issues. He replaced both batteries. (didn't solve the problem) he replaced the alternator. (didn't solve the problem) he replaced the body computer and he said that fixed the problem... I just drove it and the charging issue is still there....
The second issue is the transmission will not upshift into overdrive or downshift into first gear at a stop light. It will go into first if I manually move the shifter but will not work automatically. It starts off in 2nd gear.
If I bypass the O/D shift relay under the hood in the power distribution box... The transmission will shift into O/D and downshift to first.
Does anyone have any wiring schematics for the O/D shift circuit and charging circuit. What does the relay use to control the on/off circuit of the relay. There is no voltage to the switch circuit of the relay. Does the BCM turn the relay on with the ground or power and I was getting a pulsating signal at the relay... not a solid light on the test light... It was flickering.
I'm guessing it's controlled by the body computer but I have a feeling it may have a bad ground issue somewhere also in the mix.... Thanx in advance. I appreciate any comments or help.

 

UPDATED:..... I found wiring schematics and I was right. there is a control feed from the PCM to turn the transmission O/D circuit relay on or off. It's also the same circuit from the alternator. So without the PCM seeing a charge signal from the alternator, the O/Drive circuit relay will not be activated. I guess now it's a matter of tracing the circuits to see whats happening.

 

Double check and clean all grounds starting at the batteries to also eliminate this being an issue. 2-3 below the driverside batt, 1-2 on the pass fender and 1-2 on the firewall behind/close to the turbo.

 

I started doing that but i didn't know about some of the others you pointed out... thanx. I'll check those tomorrow.

 

If all are clean and connections are tight then ck connections at the tranny, if nothing there, it could be a solenoid in the tranny. That's about as far as my tranny experience goes.....but keep us posted on what you find.

 

I'm not getting a signal from the PCM to the energize the O/D relay or a signal from the PCM to energize the field windings in the alternator... according to the wiring schematics.... it's the same feed. When I do manually energize the relay, the transmission shifts properly. I'm trying to find out what input references the PCM has to read to send an output signal to the relay.

 

Yes...that would be the same route I'd take. You might want to check and/or reset the tps( throttle position sensor).

 

Update: There is a small electronic box (marked with "DTT") from DIESEL TRANSMISSION mounted next to the PCM. There is two wires coming out of the box. One black wire is grounded to the firewall and a white wire is spliced into the harness of the PCM. The white wire is spliced into an orange wire with a black tracer. My diagrams show that is TCC solenoid control circuit. Has anyone ever had any experience with these boxes? (GOOD or BAD) What is the purpose of these boxes?
I've left a call with the original owner to find more out about what repairs he had done to the truck b4 I bought it.
I have checked ALL the grounds from the batteries back. All connections cleaned and good.
Is it possible that the DTT aftermarket box is shorting out the PCMs and therefore not allowing a signal from the PCM to the O/D relay circuit.
Still not getting any signal to the O/D relay from the PCM or a signal for the alternator for the field windings to charge.

 

If the trans is a DTT (aftermarket) it could have higher line pressure and the computer needs to be fooled into thinking the pressure is lower - you can call DTT to get more information.