P 0122 TPS Questions

[Tom Mattison]

I had a check engine light last evening, so I had it scanned.



Should I just go ahead and replace the sensor or is the troubleshooting worthwhile?



My local AZone expert couldn't find such a device in his database, so is it a Dealer only item?



Anything special I should look for or pay attention to when trying to R/R the TPS?



TIA,

tmatt.

 

[eric huskey 2]

Do you have any engine issues or did the light come on with no other problems?

 

[Tom Mattison]

I suddenly had a check engine light when going out after having moved the ST a little earlier in the driveway.



I now have some hard shifting in the automatic tranny, which I hope is because the TPS is whacked.

 

[EddieS'04]

Try another store. TPS sensors are available after market.

Here is a project on setting the tps. If you have a VOM you can use it to test yours. At WOT you should get aproxamatly 4.7 vdc. As you open and close throttle slowly, the voltage change should be smooth and no dead spots.



edit; the tps is slot driven make shure you mount it direction of rotation.

 

[Tom Mattison]

FE04...That sounds like a pretty easy test of the sensor.



You are correct, I found it at another retailer for about $65.

 

[Kevin Palmer]

As a general rule, the later model applications such as the Trac, are not adjustable. So it pretty much is a remove and reinstall kind of job.



And yes, the TPS will affect the transmission as the ECM/PCM thinks it is either being floored or going slower than it really is for example.



Check the plug connection and the wires going to the TPS pretty well.



Also, remove the TPS and see if it is nice and dry. If so, then the TPS probably did fail.



If it is wet, there is a seal that separates it from the intake, I have seen this seal fail and allow liquid to enter the TPS and create the failure..



On the older styles, the seal would fail and allow fuel into the sensor creating the failure..

 

[Todd Z]

I have about 20 TPS sensors here all used, if you want to save $$ and go with a use part...



But scan the Computer and as long as the code is for the TPS and the plug is not loose, change the TPS...



Todd Z

 

[Kevin Palmer]

Also, most garages have scanners that will allow them to see live feed.



TPS diagnosis is easy to see as you simply turn the key on, slowly move the fuel pedal while you watch the TPS data-stream. If it is smooth and progresses in volts, it is good.



If it jumps around or stays at one voltage it is bad.



It can also operate but exceed voltage which will pull the code as well. This happens when the winding overlap each other and increase the voltage.

 

[Tom Mattison]

Thanks for the suggestions. I'm going to try FE04's DigiMeter test this evening to see what voltage is actually coming out of the TPS and also inspect the wiring.



ToddZ, thanks for the offer, but I'll pick one up locally tomorrow if I need to replace. I don't want to drive it too much on a (possibly) failing sensor.



I assume I should disconnect the battery to clear the code after messing with the TPS.





tmatt.

 

[Tom Mattison]

I tested the TPS tonight. I had a solid 1.0 at 'idle' and 4.61 at WOT. The voltage changed smoothly through cycling the throttle.



Does that really indicate a 'bad' sensor? It sounds a little low at wot, but otherwise seems to work. Should I clear the code and see if it runs any better?



The wiring looked OK. I wasn't inclined to strip it out of the loom all the way back.



Any thoughts here?



Regards,

tmatt.

 

[EddieS'04]

I would loosen it and bring the voltage alittle below 1 vdc at closed throttle. 1 vdc is right at the point that the ecu flips from open to closed loop parameters. Below 1 vdc the computer uses a different set of parameters for idle. Above that(closed loop) it uses different parameters to control the engine.

 

[EddieS'04]

Also you can unplug it and test it the way you would a varible resistor. Make sure the resistance is stable and no dead spots. I dont remember the resistive values from open to closed throttle. Verifify a smooth varible change.

 

[Tom Mattison]

Thanks FE04! I'll see if I can tweak it this weekend. I've driven it since testing (which involved connecting/disconnecting the harness from the sensor several times) and the shift points have smoothed back to normal. I suspect either a marginal sensor or a marginal connection, not a hard failure yet. I have yet to clear the code, so that is next to see if it reappears. The sensor voltage sounds like it is just barely within good operating parameters. I'll watch for a few days and see if the situation changes.



Thanks to all for the help!



Regards,

tmatt.