Overdrive button works OK truck just stays in third.
The TPS Sensor checked out perfectly.

When I checked for 12 volts on the overdrive solenoid connector with the key on - engine not running - I got about 7 volts, not 12.

Any advice? Thanks.
Randy

 

How long have you had this problem? Did you do anything to the truck prior to losing overdrive? Explain how you tested the TPS please. You should have close to 12V on the power wire to the solenoid. The PCM applies ground to the solenoid to activate it, so a good ground signal is just as important as a a good power signal. You can test the solenoid by measuring the resistance. It should show 11-15 ohms. Or you could use jumper wires and listen for a click (probably better done with the tranmission pan off). You should also look at the temp sensor (in the cooler line) and the wires going to it, as the PCM won't allow OD if it thinks the fluid is too cold or too hot (or can"t get a temp reading).
Good Luck!

 

Thanks Red Chevy 44. I'm gonna go with the temp sensor. But I tested the TPS with a meter and it checked out perfect with a method I found here on this site.
Randy

 

There are 2 temp sensors, the second is just forward of the engine temp sensor at the back on the left side of the block and hard to see. Both sensors are switches and have to be closed for OD to work. The ECM/PCM supplies 5Vdc to the TPS. On the TPS, the wire furthest forward is ground, the middle wire is the return and should be set at 1Vdc to ground with the throttle in the idle position, the furthest aft wire should have 5Vdc on it. I just went through a lot of grief with my 92 and finally bypassed it all.

 

Thanks Cougar,

Your TPS test sounds fine - and it worries me.
Cause I used another test method I found on this site
and it contained different voltages. And it all checked
out according to that test.
Wonder if it is the difference from your 92 and my 93 D250?
Anyway - I'm going to look at the second temp. sensor you mentioned.
Was bypassing everything difficult?
D250junkie=Randy

 

The 92 and 93 are the same. The 1 volt I noted is out of the factory service manual and is a "starting point". Depending on where you want it to shift it could be a little +- of that. There are a number of ways to bypass the ecm and how will depend on if you have a TPS failure or an ecm failure like I did. You will find the way I did it under the thread "https://www.dieselbombers.com/1st-generation-dodge-cummins-89-93/113772-retaining-stock-over-drive-switch-function.html" in this section. I got a little more elaborate about it, but you can use a toggle switch instead for an over ride.