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My brother recently bought a bone stock 1998 SE with a auto transmission. He's not swapping to manual. On the way home the car drove great. However once it sat when eating dinner and leaving it would not shift out of first. Limped it to a store to get some tools and such. Came out and it shifted fine. It's done it several times since owning it. He has to pull over and turn the car off then on and it'll shift. We've done a transmission flush and fill with filter. He's also had a new TPS put on. We ran the diagnostic OD/OFF thing and showed no codes. He does have a CEL on for Speed Sensor. All his gauges work fine. Could the Speed Sensor cause this issue with not upshifting?? Thanks for any help guys.

Josh.

Absolutely.

There are 2 sensors. If the input or output sensors don't agree or experiences electrical issues, it impacts the operation of the entire transmission.

Ok thanks we'll look into those immediately.

Where is the input located? The car has a code for the output. Changed that. Cleared code. Drove, code came back.

Are you using the FSM? What code is showing and coming back? I don't know input output sensors being only 2, but I do see input and output for the system described on page AT-28. Here's a link if you haven't already found it:
http://www.nicoclub.com/service-manual? ... sx/1998/at

P0720 is the code.

Swapped TCM's with my 98. Drove and it shifts. CEL came back on. Gonna check tomorrow to see if it's the same code.

Put another TCM, Speed Sensor and TPS. Still throwing same code. Any clue guys?

Also note the speedo does work just fine.

Having a spare tcm is kind of nice I suppose. Have you performed the diagnostics for your specific code P0720? Were the wires good? Was the revolution sensor good? Did you get proper voltage while driving around? I'm glad speedometer is working, that's another related issue I would have looked at next. I'm not sure about your speed sensor replacement. Maybe you can get a refund for that part. It seems to only be used when the revolution sensor is not working, which seems to be the source of your issue.

Testing the harness is next. We have spare parts because he's basically using my 1998 Kouki as his parts car. Lmao. It's an auto also ATM. So so far we've installed new Speed Sensor. Throws same code. Swapped TCM's. Throws same code. Swapped Speed Sensor from my perfectly running and shifting Kouki to his. Throws code. Swapped my ECM into his. Throws code. Attempted to check the trans codes via OD flash method. It shows no codes. Lol. We're gonna check all the wiring and if it checks out I'll put my transmission into his car. (I'm planning a 5spd swap, just hadn't planned on doing it now.) Thanks again guys.

Okay. Maybe stop clearing codes to see if any additional codes appear. Have you looked at the failed shifting diagnoses? Like I look at pages AT-92 and on. Sure, they sometimes throw codes, but I'm thinking you keep clearing yours so maybe they aren't having time to register. 2nd gear caught my eye first, but maybe 1st gear and others are affected. It mentions things like fixing or replacing the shift solenoids and or control valve assembly. Now, I'm not too familiar with the Auto, but since you have two, can you swap over those assemblies possibly?

That would be after checking wires. Those low down tranny wires get a lot of road exposure and may have become damaged, shorted or loose at the connectors. Checking the wires per the FSM seems like a good idea.

PS - sorry I was unclear on speed sensor stuff. I couldn't tell if the revolution sensor was the same or in addition to a speed sensor. The revolution sensor detects the parking pawl thing, I wonder if that could be gummed up, but figure it isn't since you seem to get correct speeds on your speedometer.

Thanks for all the help and sorry for the late response. It was the revolution Sensor. We couldn't find a new one to replace it so we unplugged it and the car has been running and driving like new. Thanks again!!!!

Oh cool! Thanks for the feedback. Are you going to replace the sensor eventually or just leave it unplugged?

Leave unplugged for now. I'm swapping my 98 soon so he'll have the Sensor from mine then. We haven't been able to find a new replacement sensor.