Hey all,

 

I'm having some issues with my 1997 Legacy Brighton Automatic wagon.

 

I took the TPS off to clean it (been having some rough idle issues) and now I'm trying to get it readjusted. At first I thought that I was supposed to do the continuity/no continuity test but after further reading I believe I'm supposed to use the voltage test instead since I have a three wire sensor.

 

From what I've read, you can either backprobe at the sensor or use pins 24 and 25 at the ECU and then look for 0.5 volts with the throttle closed, then up to 12 at full throttle. Does that sound correct?

 

Backprobing at the sensor gets me 5 volts for the most part. Adjusting the sensor doesn't get me to 0.5 volts no matter what I do. And then when I open the throttle all the way, it never changes from roughly 5 volts. It might vary a little bit, but never hits 6 volts and definitely never hits anywhere near 10 or 12.

 

If I keep turning the TPS, I can hear what I think is the IAC start activating. But I'm still at 5 volts at that point.

 

Does anyone think I would get a different reading at the ECU? If so, I'm a little confused about finding pins 24 and 25. I have the schematic from the FSM, but I don't know if that's looking at the back of the ECU connector (where all the wires enter the connector that comes off), or if it's looking into the ECU connector, or?

 

Also, if I disconnect the ECU connector to get a better look at it, is that the same as resetting the ECU? Is that bad? Anything to worry about?

 

Thanks in advance!

 

opus

I think you either have a wiring problem, are probing the wrong pins, or the sensor is not mechanically engaging the throttle mechanism. (Been a long time since I've pulled one, so I don't remember if the shaft can break or not be engaged)

 

Basically, for the 3-wire TPS sensors, there's a 5 volt input pin, the "wiper" pin which has a variable voltage depending on the shaft position, and a ground pin. Make sure the ground pin is in fact grounded. (you can measure the voltage from the ground pin to a known ground like the engine block) If the ground pin measures closer to 5 volts, you have an open ground connection. You should probably check the voltage at all three wires. I'll bet you'll be able to figure it out.

 

 

Nathan

I will need to look at the wiring diagram, but that procedure sounds screwy if they're talking about the TPS voltage hitting '10 or 12' I'm just about positive that the TPS shares a 5 volt reference voltage with the other engine sensors.