superdodge

overdrive problems driving me over the edge.


shortly after i bought the truck the injector pump started leaking. took it into an injection shop and had it repaired. a little while later it started shifting out of overdrive whenever it felt like.

i would wiggle the wiring harness between the battery and the firewall and the problem would go away. the regularity increased to the point where it was undriveable. so i went after the vacuum lines... that result in the problem going away... but coming back again and getting worse to the point where nothing in the vacuum system could be the problem.

so i do a search and find out that the tps is an ongoing problem with these... so i do the tests and it checks out fine.

but while i'm messing with the tps, i notice that if i wiggle the harness in the area of the tps and the wires that go down toward the crankshaft at the front of the engine there is a clicking noise from the drivers front fender as if there is a solenoid kicking in and out.

so i take the harness cover off and start looking for broken/missing insulation etc but cannot definitively identify the source of the problem that causes the solenoid to kick in and out.

so i take it for a test drive and no overdrive at all.

i go back to my manual and see that there is a a wide open throttle solenoid on the drivers side firewall but no indication of exactly what it does.

is it possible that some sort of short in the harness between the tps and the wide open throttle solenoid is causing this? i'm not sure exactly how to read the schematic.

what happens if i disconnect the wot solenoid, or how exactly would i do that (which wires to disconnect) also, there are a number of solenoids on that fender and now i can't wiggle the wires to cause the short so i can't identify which one it was.

any ideas?

superdodge

one other option is to simply put a toggle or push button switch on the gear selector until i can find a 5 speed.

how exactly would i wire that to the o/d unit?

Bob

wannadiesel

It sounds to me like the crank sensor wiring is flaky. That will make the PCM think the engine is not running. Check that out.

Here's a helpful list of stuff that can cause OD trouble: https://www.dieseltruckresource.com/...77&postcount=2

superdodge

thanks Dave.

i get a code 12 and 24.

i have checked the tps already, it shows .62v throttle closed, 3.5v throttle open, no spikes or drops.

i did notice that the plug itself, once disconnected from the tps, had 4.92v on the center port, .01v on the port closest the front of the truck, and 4.99v on the rear.

its kind of frustrating not being able to trace the problem to a specific wire... or would it have to be the orange one?

doesn't it seem that the problem is down stream of the tps? the problem is i don't know what is downstream.

no point plugging a potentiometer into the harness if will just be buggered by the same wiring problem.

do you know where those 3 wires from the tps end up?

Bob

wannadiesel

Seems like the TPS wiring is the most likely culprit since wiggling the harness affects the OD operation. If you disconnect the PCM you can connect your ohmmeter to each end of all three wires and wiggle/flex the harness. That should point out your bad wire. The colors are the same in the PCM connector.

superdodge

sorry, i was editing while you were answering.

i will try find pic of pcm and go from there.

Bob

superdodge

talk about opening up a can of worms.

i could only find 2 of the 3 wires from the tps at the pcm, so i decided to replace them between the tps and the plug at the rear of the engine.

i checked resistance and one of the wires grey/white was fluctuating. i put in a jumper from about 1 1/2 inches off the plug and about 1 1/2 inches from the junction plug... no change. still error code 24 and no o/d.

so i spliced the other two wires between the tps plug and the junction plug.

now i have the following codes 12, 24,24,23,22,45 and my speedometer is jumping all over the place... and, of course, still no o/d.

it seems like i'm losing ground here.

Bob

superdodge

a couple of other things...

when i go to start it, the manifold heater cycles, the the 'wait to start' light starts flashing.

also, after i spliced the tps wires, i forgot to plug the junction back together before starting it.

do i maybe need to reset the computer?

wannadiesel

It sounds like you have a bad connection in that connector now.

The computer remembers trouble codes, but it does not hold them against you. If everything is plugged in and working right it will be happy regardless of how messed up things were the last time you turned the key.

superdodge

i went backwards until most of the bad things went away.

trouble at the tps plug... no way around it.

decided to go with shifter switch.

i put a toggle on the shift lever, connected first the front pin, then the 2 outside pins of the transmission plug together to one side of the toggle, grounded the other side.

i have about 7 volts at the center pin with the ignition on. still cannot cause o/d to engage.

the bottom line is that i need this thing to run on the highway, the rest is all peripheral.

why can't i get o/d to engage?

do i need to run 12v line to the center pin, then ground the outers?

Bob

superdodge

okay, got the neutral/reverse switch wired back together :sheesh:

still can't see where the plug is that i need to splice into...

wannadiesel

It's a little further back, only has 2 wires. All you need to do is supply ground.

superdodge

i found the plug, wired the orange to the downstream side of the lighter fuse, dark wire to my ground toggle... all is good.

so i'm back in business, albeit manually shifting o/d but that's okay.

i can't believe things went so bad so quick.

it looks like that the black/blue stripe wire is used for a whole bunch of different things, mess with that and all hell breaks loose.

oh well, thanks for the help.

Bob