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After replacing the TPS on my '97 2.2 A/T with one from the junkyard I declared my car repaired from it's transmission problems and P0720 (output speed sensor circuit) error code.  It initially drove and shifted wonderfully (no CEL).  However 50 miles down the road it was back to it's old ways going into "limp mode" 2nd gear selected.  I unplugged and reattached the electrical connectors to the transmission and was in the process of back-probing the TPS when I accidentally touched the wrong probe--which showed I was getting continuity across the terminal with the ignition off. This seems to be wrong--what say you?  

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You'll have continuity across the TPS regardless of ignition switch positions. Its a potentiometer, so all three pins are electrically connected inside. This you will always see continuity to all three pins with a properly working unit. The resistance from pin to pin varies as the sensor sweeps.

 

 

After replacing a TPS, you have to adjust it so the ECU receives the proper signal voltage at closed throttle.

Back probe the center pin of the TPS and twist the sensor until the voltmeter reads 0.50-0.55 volts.

After adjustment unhook the battery negative for about 10 minutes to reset the ECU.

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I have always worried about my VSS getting mangled accidentally doing a trans service, but not yet...

if its not the tps...

if your VSS has been pulled on or strained you could have a similar fault as to one i found on a 2000 outback engine wiring harness. the owner complained of "shift shock" and could not drive the car reliably. after investigating and dissecting the old harness I found several incomplete breaks in the wiring... say any of those wires has 12 strands inside the plastic shielding. on her car the reference voltage wire supplying the TPS had 8 of those 12 strands broken in the same place, when the wiring during driving conditions bounced around the broken strands would seperate slightly bringing up the impedance and only allowing 2.4 volts to travel to the TPS... so the cars computer is supposed to be comparing the tps voltage to a constant 5v but if the constant 5v turns into 2.4v suddenly the car thinks 2.4 volts from the tps is full throttle and tries to shift to compensate... big bad slam screech from the trans...

 

I'm not suggesting you have THIS problem but if the wiring to your VSS is slightly broken it could account for the intermitant code .

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