TPS (Throttle Position Sensor) readings?

[V8killR4U]

My GN just recently started experiencing hard starts. I checked the TPS reading in the key on position and the readings were jumping .35 to .59. and at WOT treadings were jumping around as well 4.37 to 4.69. I purchased a new TPS installed it and the same thing occured....

What would cause TPS readings to bounce around like this? Where else should I look? This is driving me nutz!

Also even if the sensor is unplugged it reads .01 to .10....

 

[mikestertwo]

Check your grounds at the back of the head.

 

[V8killR4U]

Need some more ideas. I will check the grounds. Would that still make the tps reading jump around?

 

[mikestertwo]

Would that still make the tps reading jump around?

Yes it would. Unstable readings is usually a bad connection somewhere. I would start at the grounds then the connector itself at the tps and the connection at the computer.

 

[V8killR4U]

How do you verify grounds are good. What is the procedure?

Any other ideas....

 

[Razor]

Ground and power are references. See the TPS works with 5 volts. The voltage is steady from the ecm. If its not, then it can go up or down based on that.

Just like the ground is a reference. Ground is suppossed to measure zero in relation to chassis. A few .10ths will happen on some circuits depending on load.

Example TPS is suppossed to read .42 volts. With power at 5 volts and ground at zero. If the ground is dirty and now reads .1 instead of zero, the TPS will go from .42 to .52 as its reference increased .1. Just like if the 5 volts goes to 5.5 volts.

Way to test is get a digital volt meter and clip the black to battery negative, then pierce the black wire on the TPS. Start the car and measure voltage on the black and gray wire at the TPS. Black is suppossed to read zero and Gray is suppossed to read 5v DC.

Bad computer can also do this, corrossion on computer socket/terminals, bad ground back of head, bad ground at the body connection from engine to body, etc.

 

[V8killR4U]

Ground and power are references. See the TPS works with 5 volts. The voltage is steady from the ecm. If its not, then it can go up or down based on that.

Just like the ground is a reference. Ground is suppossed to measure zero in relation to chassis. A few .10ths will happen on some circuits depending on load.

Example TPS is suppossed to read .42 volts. With power at 5 volts and ground at zero. If the ground is dirty and now reads .1 instead of zero, the TPS will go from .42 to .52 as its reference increased .1. Just like if the 5 volts goes to 5.5 volts.

Way to test is get a digital volt meter and clip the black to battery negative, then pierce the black wire on the TPS. Start the car and measure voltage on the black and gray wire at the TPS. Black is suppossed to read zero and Gray is suppossed to read 5v DC.

Bad computer can also do this, corrossion on computer socket/terminals, bad ground back of head, bad ground at the body connection from engine to body, etc.

Thanks for the info Razor. Would these jumping TPS numbers (bad grounds)cause my hard start more than likely?

 

[V8killR4U]

Could these bad grounds possibly be causing my issue with the green injection light issue I was having that I called you about the other day..... (Green light doesnt come on until late 15lbs-20lbs and sometimes not at all) Sounds like it is considering there are no leaks and wiring is correct from PAC to Pump.....

 

[Razor]

Could these bad grounds possibly be causing my issue with the green injection light issue I was having that I called you about the other day..... (Green light doesnt come on until late 15lbs-20lbs and sometimes not at all) Sounds like it is considering there are no leaks and wiring is correct from PAC to Pump.....

Absolutely, as the computer works off of sensors to make it's decisions.
Garbaje in garbage out.

Sounds like you have some electrical issues on the car.

 

[Rodney87GN]

Definitely check the connections at the ECM.

I recently solved my erratic TPS readings by replacing the ECM... the pins on the ECM had moderate corrosion that's pretty much impossible to clean off.

You can try this...with the key on, engine off slowly move the wires at the ECM back and forth (you may have to take the ECM out of the kickpanel) and watch your TPS on your scan tool for any changes. If theres any then you know you don't have a solid connection.

On my car the corroded ECM connections screwed with my TPS and O2 voltages. If i found the "sweet spot" to hold the wiring harness in place then it was all good but as soon as i hit a bump it would get knocked all out of whack. Also in the past I had a broken wire on the TPS connector and had to get a new pigtail.

Our cars are old enough that these electrical gremlins can be frustrating to troubleshoot while you're left stranded on the side of the road.

 

[DR BOOST]

Ground and power are references. See the TPS works with 5 volts. The voltage is steady from the ecm. If its not, then it can go up or down based on that.

Just like the ground is a reference. Ground is suppossed to measure zero in relation to chassis. A few .10ths will happen on some circuits depending on load.

Example TPS is suppossed to read .42 volts. With power at 5 volts and ground at zero. If the ground is dirty and now reads .1 instead of zero, the TPS will go from .42 to .52 as its reference increased .1. Just like if the 5 volts goes to 5.5 volts.

Way to test is get a digital volt meter and clip the black to battery negative, then pierce the black wire on the TPS. Start the car and measure voltage on the black and gray wire at the TPS. Black is suppossed to read zero and Gray is suppossed to read 5v DC.

Bad computer can also do this, corrossion on computer socket/terminals, bad ground back of head, bad ground at the body connection from engine to body, etc.

your so sexy when you talk all electrical:wink:

 

[DailyDrifter]

+1 with Razor.


I had a car that was throwing out codes like it was going out of style (No check engine light). Found out that the cal-pac pins were "tweaked" and the chip that was sitting in the car was bad , put a stock chip in and everything was reading good. Also the wire harness had some corrosion in the pins. What was wierd is with KOEO when the tps would go over 2 volts, it would throw ESC, eprom, Cal-pac, MAF, Cam signal codes . That car was fun to diag.

 

[V8killR4U]

Definitely check the connections at the ECM.

I recently solved my erratic TPS readings by replacing the ECM... the pins on the ECM had moderate corrosion that's pretty much impossible to clean off.

You can try this...with the key on, engine off slowly move the wires at the ECM back and forth (you may have to take the ECM out of the kickpanel) and watch your TPS on your scan tool for any changes. If theres any then you know you don't have a solid connection.

On my car the corroded ECM connections screwed with my TPS and O2 voltages. If i found the "sweet spot" to hold the wiring harness in place then it was all good but as soon as i hit a bump it would get knocked all out of whack. Also in the past I had a broken wire on the TPS connector and had to get a new pigtail.

Our cars are old enough that these electrical gremlins can be frustrating to troubleshoot while you're left stranded on the side of the road.

Well switched ECM's and the problem didnt go away but it did get better. TPS numbers were way more stable. would only jump .44 - .46 (IT would only read one or the other, not .45)

Shouldnt this number stay to whatever it is set too and not jump around?