240sx automatic transmission tcu ?

[1hotsilvia]

I recently posted on doing a transmission swap into my car. It wouldn't go into 1st or drive. I'm pleased to report that it now goes into all the gears reliably.

But still if I drive agressively, I mean reallllly agressively it will lose drive sometimes until you turn the car off and on again.

I've been trying to find info on how the tcu works. I believe this may have alot to do with the problem.

If anyone knows how the tcu works, what sensors and info runs it, and if there are any factory set safeguard settings that may cause my car to act this way. let me know.

Also can you suggest a piggyback controller that would work well to let me drive this trans. more agressively.

[NISTECH]

the transmission makes its decision to shift based on tps input and speed sensor input. If either your tps or your speedometer are going flaky the trans will go into a failsafe, typically 3rd gear.

[1hotsilvia]

I work at an aut parts store and I have info on how to test most tps sensors. However, I do not have access to a test chart for my own. Can you tell me how to test this tps if it is a testable tps. Most just involve turning a screwdriver slowly in the tps and returning it back to it's original spot and checking voltage with a sensor tester plus. Is this one the same?

Thanks for the info I've gotten so far.

[NISTECH]

the way I test them is with it plugged in and car off, back probe the center wire(typically white) the car must have been previously warmed up but off during the test.key in the on/ run position. at rest the reading should be between .3 and .7volts(.5v is ideal) then watch your meter as you slowly rotate the throttle to full throttle position should pass 4.0v with no hick ups along the way. Most tps failures tend to occur at the just off idle position in the sweep since at cruise speeds that is where it usually sits and wears that area in the sensor more. so when conducting the test pay particular attention to what it does in that range and go through that area very slowly as the sample rate on your meter might not be fast enough to catch a glitch as you rotate through it.

[240ROCKER]

NISTECH,Could it be possible for the ECU (not the TCU) to not give the proper signal to the TCU to shift? I have got the intermittent shift problem from first to second on my auto transmission 240sx and I have narrowed it down to something electronic and not mechanical.

I know it's electronic instead of mechanical because I put an LED on the output of the TCU (pin 6) that goes to Solenoid 'A' (first to second gear solenoid). During normal operation, when the transmission shifts to second the LED turns off, telling the transmission to shift to second, but when it doesn't shift and is supposed to, the LED remains on, which means that the transmission is not getting the signal to shift.

According to what you stated earlier, "the transmission makes its decision to shift based on tps input and speed sensor input. If either your tps or your speedometer are going flaky the trans will go into a failsafe, typically 3rd gear". Well...when I started having this problem, I replaced the TPS and that didn't do any good and I have also installed a remanufactured TCU. That didn't do any good either. I was told that if it was the speedometer, then I would notice a very erratic backward and foreward movement of the needle whenever it was stuck in first, which I haven't noticed.

This is why I was wondering if maybe the ECU could be somehow sending an erroneous signal to the TCU. However, whenever I pull the codes on the ECU, it thinks everything is fine and gives me a '55' code, which tells me no errors. Any thoughts on this, I'm really scratching my head on this one???

Thanks!240ROCKER

[NISTECH]

what year is your car 240rocker?

[240ROCKER]

1992 240SX

[NISTECH]

240rocker I read your other post where you have been chasing this. and from all the input you guys had in it I think its a grounding issue with the solonoids , read my post in that thread. its in verts forum I think.