TPS Voltage problem...Bad TPS?

[Hot Air 85]

I have an 85 Hot Air with the TPS way out of whack...scan tool shows 4.31 volts at idle and 4.41 at WOT. This is the max of the adjustability, I cannot get it any lower of higher regardless of movement. I have a really good feeling the scan tools right because it's pig rich in closed loop.

Does this mean I have a bad TPS?

If I have a bad TPS can I use the 86-87 unit?

I went to advance auto(it's local) to price a new sensor and they wanted $262.00 for the 85 sensor and $56.00 for the 87 sensor.

Any advice is appreciated, I didn't expect the TPS to turn into the $200 question.

Thanks, Jeff

 

[mikestertwo]

Sounds like the ground side wire on the sensor is open or the sensor is bad. Put a volt meter on the low side of the sensor. If it's reading close to 0 volts yet your getting over 4 volts all the time on the output, then your tps is bad. If it reads close to 5 volts, then you have an open ground wire. Also, check the connection at the tps for corrosion. Could just me a bad connection on the ground side.

 

[Hot Air 85]

Sounds like the ground side wire on the sensor is open or the sensor is bad. Put a volt meter on the low side of the sensor. If it's reading close to 0 volts yet your getting over 4 volts all the time on the output, then your tps is bad. If it reads close to 5 volts, then you have an open ground wire. Also, check the connection at the tps for corrosion. Could just me a bad connection on the ground side.

Two things 1) what wire is for the "low side" 2) where does the TPS ground out?

This is agin for a HA car if it matters.

 

[mikestertwo]

I'm not that familliar with the Hotair cars but I think the color codes are the same on the TPS as the intercooled cars. Grey should be +5v, Black should be ground, Blue should be signal out to the computer. Where it's grounded, I don't have a clue. Most likely, somewhere on the block. Maybe someone else could chime in on this.

 

[Hot Air 85]

Sounds like the ground side wire on the sensor is open or the sensor is bad. Put a volt meter on the low side of the sensor. If it's reading close to 0 volts yet your getting over 4 volts all the time on the output, then your tps is bad. If it reads close to 5 volts, then you have an open ground wire. Also, check the connection at the tps for corrosion. Could just me a bad connection on the ground side.

I have 4.02 volts at the blue signal wire, and 0.00 volts at the grey wire. just to clarify this means bad TPS yes?

Thanks for your help on this, Jeff

 

[mikestertwo]

I assume you mean 0 volts on the black wire. Yes, that means that the TPS is bad. The grey wire should have 5 volts on it. You are measuring the voltages with the connector connected to the TPS, correct?

 

[Hot Air 85]

I assume you mean 0 volts on the black wire. Yes, that means that the TPS is bad. The grey wire should have 5 volts on it. You are measuring the voltages with the connector connected to the TPS, correct?

I have 0 volts at the grey & black wires 4.02 at the blue, this is measuring with the TPS connected and key turned on engine off.

Thanks, Jeff

 

[TurboDave]

I have 0 volts at the grey & black wires 4.02 at the blue, this is measuring with the TPS connected and key turned on engine off.

Thanks, Jeff

That's confusing!! The dark blue wire if memory serves is supposed to be the TPS output to the ECM, Black is ground, and Gray being the 5v reference supply to the TPS.

With no supply to the TPS on the gray wire, how can you read an output on the blue wire????

Or do I have my colors reversed (no reference to look at here at work)

 

[mikestertwo]

That's confusing!! The dark blue wire if memory serves is supposed to be the TPS output to the ECM, Black is ground, and Gray being the 5v reference supply to the TPS.

With no supply to the TPS on the gray wire, how can you read an output on the blue wire????

Or do I have my colors reversed (no reference to look at here at work)

I'm with TurboDave, something doesn't sound right. You should have +5v on the grey wire, the blue is the signal wire to the ECM, and the black is ground. How are you measuring the voltages, between which wires, or are you measuring to the engine block?

 

[Hot Air 85]

I'm with TurboDave, something doesn't sound right. You should have +5v on the grey wire, the blue is the signal wire to the ECM, and the black is ground. How are you measuring the voltages, between which wires, or are you measuring to the engine block?

Block or frame as ground red probe to wire....maybe I didn't get it far enough in there to read the 5V...i'll try again tommorow and post the results.

I really appreciate the help...

Thanks, Jeff

 

[mikestertwo]

First, use the black wire as the ground and measure the blue and grey wires. Then use the block as a ground and measure all three wires then post back the results.

 

[BRAD_PADGETT]

I think I can help here since I have a hot air. The wiring on the 87/87 is the same as a hot air(except MAT and electric fan) only everything is in a different location. The TPS connector( not the TPS itself) wires are labeled ABC.

A. 5 volt reference signal.
B. TPS signal to ECM. Idle- .5 volts-WOT 4.5 volts.
C. Ground.

A bad TPS should throw a code 21 or 22. Your check engine light should be on. Measure the voltage on wire B -ign. on -engine off. Should be around .5 volts. Do the same at WOT. Should be above 4 volts. I have the 85 shop manual and I can send you the diagonistic charts. It is easy.

Whatever you do NEVER THROW YOUR MONEY AWAY AT ADVANCE. Postons sells a new 85 TPS for $35 or even better get a used one from GBODYPARTS. I am sure Kirbans sells one cheap as well. If needed I can email you the GM diagnostic charts. Good luck- Brad

 

[Hot Air 85]

First, use the black wire as the ground and measure the blue and grey wires. Then use the block as a ground and measure all three wires then post back the results.

Black as ground
Blue 4V
Grey 5V

Block as ground
Black .3V
Blue 4V
Grey 5V

 

[TurboDave]

Black as ground
Blue 4V
Grey 5V

Block as ground
Black .3V
Blue 4V
Grey 5V

Are you sure the Blue wire is reading 4v and not .4v ?? If it is reading 4v then you have a bad TPS.

 

[Hot Air 85]

Are you sure the Blue wire is reading 4v and not .4v ?? If it is reading 4v then you have a bad TPS.

Yes it's 4V....Does anyone know if the 86-87 TPS is any different than the 84-85 model?

 

[mikestertwo]

Yes it's 4V....Does anyone know if the 86-87 TPS is any different than the 84-85 model?

Your TPS is bad! The sensors are different. I think the arm is different. Someone else can verify that as I'm not sure.

 

[Hot Air 85]

Thanks

Thanks to all for the help. Looks like i'll track down a TPS, but your right screw advance I was just on Postons site and $35.00 ain't too bad.