89 3vz-e automatic

I have an ongoing problem that is driving me crazy. Typically, at a cold start my coolant temp sensor does not register. The temp gauge registers below bottom and the check engine light comes on. After driving 30 seconds the gauge registers the correct temp however the check engine light remains on. Normally, perhaps 8 of 10 times I have to shift manually, as the trans will not downshift. Nor will it shift into overdrive. This problem seems to fix itself after about 5 miles of highway driving. Last week I replaced the speedo cable thinking this would solve the problem but no such luck. Before the new cable the OD light blinked all the time. Now it blinks sometimes. Normally I get diagnostic code 22 for the coolant sensor. However after clearing this code I sometimes get 41 TPS and 51 Switch condition signalààBecause of the codes my thinking is the Trans problem is electrical. Any comment are welcome. Thanks All

http://personal.utulsa.edu/~nathan-buchanan/93fsm/autotrans/31diagnosi.pdf Give that a look; it's from the FSM sticky'd here, which should also help you.

Make sure your coolant is topped off.

Why was the OD cable replaced?

Thanks kewlynx for your reply and the link to the transmission codes. I'd not seen that before.


Why was the OD cable replaced? [/quote]

The speedometer cable was replaced because it was broken and not functioning for about 3 months. Seemed to me that it was the beginning of theses problems.. Perhaps not.

these trucks have a fail safe that blocks out O/D until the car is 170 degrees operating temp. If the O/D blinks there is an electrical fault in the transmission usually the solenoids if you have an a340f there are 3 and ana A340H there are 4. but the whole thing is if you tps is not working correctly the truck will barely shift either. and the same with the coolant temp sensor since that acts like a switch for the o/d. i want you to read codes again. and count the blinks on the o/d light if it pulses there is no codes but i think you will find a code 62 63 or 64. i recentyl went thru the same battle but from my solenoids being bad they mechanicly messed up my trans now i have a 5 speed!!

in the mean time check this out
link on how everything works http://autoshop101.com/forms/h16.pdf
diagnosis and repair
http://autoshop101.com/forms/h17.pdf