No overdrive issue!

[Beach]

I need some advice from you first gen. guy's. My boss ownes a '92 W250 cummin's 4x4, auto, LE. He say's it won't go into overdrive and want's to know what the problem could be. I hope the discription is all you need to diagnose the problem, I don't know much about first gen's, I owne a 2nd gen. Thank's for any info.

 

[BushWakr - RIP]

The 3-4 and, 4-3 shift are controlled in large part by the TPS solenoid. It's the thing mounted on the top/front of the injection pump. It has a 3 wire connector on it.

If you do a search on 'adjusting the tps' you'll find a good "how to" for it.

Often times the thing is out of adjustment or sticky and that will give you OD trouble.

If you can't find the instructions let me know and I'll email them to you... just give me your email address of course. .



pb...



ps: here is link to pictures of the TPS in my readers rigs photo gallery... .



https://www.turbodieselregister.com/user_gallery/displayalbum.php?&userid=5168&albumid=489

 

[Beach]

Thank's for the detailed info! I will pass this on and hopefully we can get the O. D. to work again. I appreciate your help!

 

[EZeis]

The trans shifting and overdrive are controlled by the following: Engine coolant sensor, keeps trans locked out of overdrive when coolant is below 60 degs. Transmission thermo-switch (located on the trans cooler line) will lock trans out of overdrive if trans fluid is above 273 degs. TPS, overdrive lock out switch on dash, overdrive solenoid in trans and VSS as well.



Also you can pull codes from the PCM by switching ign switch on-off-on-off-on and count the flashes of the check engine light. Code example, lamp flashes 4 times, pauses and flashes 1 more time, it's a code 41. Codes will clear once fixed after 51 engine starts or use scan tool to clear codes. Code 55 is completion of trouble code display.



Codes are:

11 No reference signal during cranking-engine speed sensor.



15 No Vehicle speed signal-VSS.



22 Coolant sensor voltage low or high.



23 Charge air temperature sensor voltage high or low.



24 TPS voltage high or low (auto trans only).



33 A/c clutch relay circuit



34 speed control solenoid circuit



41 alt. field not switching properly



42 Auto shut down relay control circuit or no ASD relay voltage sense at PCM



45 Overdrive solenoid open or shorted (auto trans only)



46 charging system voltage too high



47 charging system voltage too low



53 internal PCM failure



55 completion of trouble cold display



62 PCM failure, SRI miles not stored



63 PCM failure, EEprom write denied



Don't forget, bad grounds as well.



Earl