Finally got a DTC out of this car i've been trying to troubleshoot.

P0122 - TPS circuit low voltage

The TPS its self has been replaced with a Blox TPS and calibrated. I believe the problem may be with grounding? There is a good 5 volt reference voltage across the connector and the TPS is still .5v - 4.5v

Any suggestions?

 

Bad connection, loose terminal, open wire, wonky ECU ... all possible.

Have you reset the ECU since you installed the new TPS?

 

Yes, I've used a scan tool to 'reflash' the ECU after new TPS.
Where does one start to solve this problem? Do I simply unwrap the wires in the harness and trace them back looking for corrosion and grounds?

 

FYI: I pulled the connector to the TPS. Drivability and power have increased but CEL on all the time of course. I believe the problem to be grounding related.

I am starting to think the best course of action on this would be drive as is and plan a H22 or K series swap in he near future.

 

The TPS shares a ground at the PCM with the ECT sensor and the IAT sensor. Are you getting trouble codes for those sensors as well? Did you replace the tps in an attemp to fix this problem or did this problem occur after the tps was replaced?

 

1. Disconnect the TPS and connect a voltmeter across the Green/Black and Yellow/Blue wires = 5v with the ignition on (engine off).
2. If so turn ignition off reconnect TPS and probe Red/Black and Ground wire with a safety pin, so you have a contact with the terminal inside the connector = .5v
with the ignition on and throttle close.
3. Probe Red/Black and Ground wire = 4.5v with the ignition on and the throttle at wide open.
4. While your moving the throttle you should see a smooth change in the voltage and not jumping from one extreme to another.

You can try cleaning the tps terminal with rubbing alcohol and use dielectric grease on the connectors. If that doesn't work then you have to take off the throttle body, remove the tps and recalibrate tps. I did that and it worked.

 

Bump from the dead....

The TPS sensor its self is new and re-calibrated .5 closed, 4.5 open, good 5 v reference. The issues appears to be in the wiring forward of the sensor or the ECU. I'm unsure how to tackle this and right now i'm just driving it with all the jerking and lack of power... still getting decent mileage. Would very much like to go to K series, or just get the hell out of this car entirely.

 

First, check for bad connections at the sensor connector and ECM/PCM. Then:

1. With the ignition OFF, disconnect the sensor connector.

2. With the ignition ON (II), measure voltage between yellow/blue and green/yellow.

Is there about 5V ?

YES- step 3

NO- step 7

3. With the ignition OFF, measure resistance (ohms) between terminals 2 and 3 on the sensor side:


Is there about 0.5-0.9 ohms?

YES- step 4

NO- You need a new TPS or need to re-calibrate.

4. Measure resitance between terminals 1 and 2.

Is there about 4.5 ohms?

YES- step 5

NO- You need a new TPS or need to re-calibrate.

5. Disconnect ECM/PCM connector A (it's the bottom connector when you're looking at it inside the dash) and measure continuity (ohms) between red/black and body ground on the wire side of the connector.

Is there continuity (resistance)?

YES- Repair the short between ECM/PCM connector A15 (red/black) and the sensor. How to figure where the break in the wire is: That same red/black runs from the ECM/PCM A15 to the sensor. With both connectors disconnected and the ignition OFF, set the multi-meter to ohms and place the red lead on one end and the black on the other. If there is no reading move the black lead closer to the red lead along the wire until you have a reading. The break is somewhere between where you first got a reading and the last place you didn't get one.

NO- step 6

6. Connect ECM/PCM connector A15 (red/black)to body ground with a jumper wire and measure continuity (ohms) from the red/black on the wire side of the sensor connector and body ground.

Is there continuity?

YES- Update or replace the ECM/PCM

NO- Repair the short between ECM/PCM A15 (red/black) and the sensor (red/black)

7. Measure voltage between ECM/PCM A10 (green/yellow) and A20 (yellow/ blue).

Is there about 5V ?

YES- Repair the open between ECM/PCM A20 (yellow/blue) and the sensor (yellow/blue).

No- Update or replace the ECM/PCM.