TPS problem 95 Lesabre

[Richard S]

I have checked the Tps with a digital vom. The resistance seems to be good. I am getting a P0123 on the scanner. Voltage is what is puzzling me. Closed throttle I am getting 4 1/2 to 5 volts on the signal wire, as I open the throttle the voltage goes down. According to the manual I have the closed postion should be less than 1 volt and as it is opened the volts should go steadily up to 5 volts. Its acting backward to the manual. There is only one way to install the TPS. I don't know if I now have a computer problem or what? Any ideas would be greatly appreciated. Thanks.

[HotZ28]

OK, now let’s be sure that you have the TPS installed properly before condemning the PCM! The lever on the TPS should go under the pin on the throttle rod and move with the throttle opening. It is spring loaded! Be sure this is correct.

[Richard S]

It does. I thought there might be more than one way to install so I have checked and rechecked.

[HotZ28]

Where did you buy the TPS? (What Brand) In your other post, you said; “I have tried about 5 tps now thinking they may have made them wrong or faulty. Parts store didn't know either”.

When you installed a new one, did it work ok for a period of time? If you are getting 5.0v reference voltage to the TPS and weird output to the PCM, the TPS is not doing it's job! Are you sure that the terminal and wires are ok?

Try this; Find a nice convenient place and cut the blue wire going to the PCM. Check voltage from the TPS to the end of the blue wire that was cut. Let us know what you find.

[Richard S]

Brand is Borg Warner and I got it at Oriellly Auto parts. We also tried anothe brand whiile I was there and it did the same thing. I will try cutting the wire this afternoon. Thanks.

[Richard S]

Ok I took the computer loose and ohmed the wires from the TPS to the computer plug just to make sure. All seemed ok. I also measured the voltage at the back of the computer and it was 4.89 with no one touching the TPS as we moved it to open throttle the volts dropped to .78 at wide open. I also made a pigtail that I could plug into the tps and left wire open, not going to computer to get my readings. The gray wire is 5 v with no change as the throttle is moved. The Blue wire is 4.89 not moving the lever on the tps. Move the lever to open throttle and I get the same as at the computer .78. This is the signal wire if I understand it correctly and the black is the ground.

If I am understanding this whole thing correctly the grey wire and blue are essentially one wire in a loop and the TPS is a potentiometer. The more resistance on the tps tells the computer what is wanted. 5v ref is feed wire to tps which is the boss or operator and blue back to the computer. Is this correct? If it is the tps cant be doing its job or I am missing something.

[HotZ28]

Your concept of the TPS operation is correct! The blue wire is the signal wire to the PCM and should measure no more than .5v @ closed throttle. Borg Warner is made in Mexico and not my preferred brand, however, I have never heard of this kind of problem with them. Is there anyway you could post a pic of how the TPS is mounted?

[Blue Bowtie]

GRY is + 5VDC, BLU is the TPS signal, BLK is signal/PCM ground. Of course, BLK can only be ground if the PCM is grounded. Can you read +5VDC on the GRY wire to a good engine ground?

[Richard S]

According to the wiring diagram black is ground.

I don't understand it but I think I have figured it out. My youngest daughters car is an 84 olds cultass. It has the 3.8 in it also and I got to thinking it should have a TPS and it did. So I looked in the manual to see if it is set up the same way and it is. I measured the voltage on hers at grey and it was 5 v as it should be, then on to the blue wire .5 v at closed throttle and 4.78 at wide open. It is the same type plug so I thought I would plug the sensor off the 95 on her car. Voltage was jumping around at closed throttle in the millivolt range but at wide open throttle it was 4.78 v. I think it is time to replace the computer. I'll find out after while when the parts houses open. I'll let you know. By the way Hotz28 I think my digital camera is broken, so I don't know of a way to put the picture on here but it mounts under the throttle body.

[Richard S]

I am really stumped now. I changed the ECM and got a check engine light. Pulled the code and it is a P0123 high same as it was. Checked the voltage again and it is 4.87 at closed throttle and goes down as throttle is opened.

[Richard S]

Confession TimeBoy do I feel stupid.
I took the car to a shop to see if I was getting all the codes and I was. I had changed the pigtail and put grey to grey and blue to blue and black to black on the new pigtail. Well to make a long story short the grey and black were reversed. It now read .5v at closed throttle and 4.89 at wide open. No codes runs great. Thanks for all the help. I sure feel stupid though. I learned to check the wires for proper orientation regardless of colors.
Thanks again for all the help. By the way I was lucky and got my money back on the computer.

[Blue Bowtie]

Ha! That's an easy one. Only two wires. I've done it a dozen times. If you want to know what's REALLY stupid, try assembling a trans, hanging on the torque converter, getting it on the jack, and just about getting it lined up on the engine and the last bolts in, then clean off the workbench to discover the low/reverse clutch plate spring still sitting under the mess. THAT'S when you've earned the right to feel stupid.

(Don't ask how I know - As if you had to...)

[Jrs3800]

Yes in years of dealing with cars we have all done something that has required us to do more work... And without admitting too much... Lets just say in a couple of cases the extra added work was at least a couple of hours... Nothing is perfect...LOL

And glad to hear that you got it right