J30 transmission won't shift out of third

[aerotigger]

With the camshaft position sensor issue solved, I need to work on the transmission issue. I have a '94 J30. When I got it, it wouldn't shift into fourth. I pulled the transmission myself and sent it to a rebuilder. It worked great for a while once I got it installed then started slipping when shifting from fourth to third when passing. I pulled the transmission again. This time, it will go into reverse, park, neutral. . . but the only forward gear appears to be third. It will barely proceed from stop and never shifts. I put a new throttle position sensor, camshaft position sensor, and engine coolant temperature sensor in it. That seemed to solve the engine hesitation problem. It will take off like a shot in reverse. It just has no power going forward.

I'm open for suggestions on this new challenge. Thanks in advance for the help!

[DominickJ30]

The transmission is in limp mode.

Instead of throwing parts at this problem you need to diagnose it. Sounds like it has something to do with the TCU or other trans controls. Good luck.

[aerotigger]

Thanks, I'll let you know what I find out. It's going to T3 this week.

[aerotigger]

Follow up/clarification--I didn't "throw parts" at the last problem. I used the diagnostic procedure as specified in the service manual. All those parts were identified as out of spec so I replaced them. Unfortunately, a lot goes wrong with these cars in 320,000 miles. For a little more investigation into this transmission shift issue--I decided to break out my DMM and do a little more trouble shooting. The transmission computer wouldn't go into self diagnostic mode. So that narrowed it down to the gearshift selector discretes, the kick-down switch, or the throttle closed switch. The gearshift selector discretes and kick-down switch checked out fine. That left the throttle closed switch. It appears that my service manual has an error in the throttle closed diagnostic procedure so that was throwing me off. I finally pulled the new TPS off and put the old one back on. The computer will at least go into diagnostic mode and identify the TPS as faulty. I decided to compare the two TPSs thoroughly. The throttle position switch has three pins operating in a single pole double throw type configuration. The center pin is connected with one pin with accelerator released then switches to the other pin as the pedal is depressed.

Took a while to determine the brand-new part was faulty. That's what I get for going to AutoZone trying to save time. Hopefully, a new TPS tomorrow will help solve this problem.

[aerotigger]

The transmission self diagnostic returned a code for the shift valve solenoid B. Turned out to be a broken wiring in the wire bundle on the transmission. 10 minute fix.