How to Calibrate Throttle Position Sensor (TPS)

[BretMann]

Regarding my 1999 4Runner 2.7L base.

I recently got code of P0120 Throttle Position Sensor A Circuit. Idle became a little rough, acceleration has some hesitation. Now it's idling around 1100 rpm but varies. Starts and runs fine otherwise. Cleared the code a few times and it takes a while to come back. Sometimes it will idle and run fine, then not. The factory TPS seems to failing after 24 years and 108k miles.

My Innova scanner shows TPS of 10.6% (measure of absolute throttle flap position) at 600 to 1100 rpm idle. The graph shows it will smoothly go up or down but then a spike or two suddenly appears, although engine runs "ok". Research on replacement says I need to calibrate the TPS when I replace it.

First time I do this so I want to check with you guys first. I've read the TPS voltage at idle is supposed to be 0.5V to 4.5V full throttle. Also TPS absolute % is supposed to be 0% idle to 100% full throttle.
1- Are those setting numbers correct?
2- I prefer to use my scanner to do this because it seems it would be easier. Is 0% at idle equivalent to 0.5V and that will give me the same result?

Please confirm/clarify.

Thanks

 

[Bad Luck]

My Innova scanner shows TPS of 10.6% (measure of absolute throttle flap position) at 600 to 1100 rpm idle. The graph shows it will smoothly go up or down but then a spike or two suddenly appears, although engine runs "ok". Research on replacement says I need to calibrate the TPS when I replace it.

That's a normal percentage for idle. The spikes indicate that the sensor has failed and needs replacement. 2000 and older tps sensors don't need calibration as far as I'm aware of.

 

[BretMann]

Thanks. Interesting.

So for the calibration I need to do with the engine on and warmed up, 10.6% at 600 rpm is correct. Also, with engine Off and ignition On, 0% with no throttle and if I press the throttle to the floor I should get 100%.

Is that right?

 

[gamefreakgc]

From what I've seen from several vehicles, 10%-11% throttle at idle is correct. The only calibration you need to do is to pull the EFI fuse (not relay) or disconnect the negative battery cable. That resets all TPS and IAC data and starts from scratch.

I looked it up and the acceptable range is from 6%-20%. That seems really huge but that's what the FSM says.

 

[96RedRunner]

Something to lay eye's on before removing OE TPS.
TPS has mounting slots 1/4" long, take note of where mounting screw is in the slot, slot is covered by mounting screw flatwasher. Slots are for tweaking using meter or code reader looking @ %.

2 wks ago Runner went limp mode no check engine light, Hhmm, lucky no traffic place to pull over.
Restart got it going, week ago in traffic 300' on sidewalk n street gutter Fug.
TPS DTC resart got me rolling. Have had one in parts stash for a while been waiting for it to happen for the experience of it chitting the bed.

Mine 13% at 660 rpm idle ECT 185*F before, age probably had it off. My FSM says range is 7-11% closed 65-75% full open. Wonder what up with that.

 

[Endlessblockades]

Never knew calibration was an issue/option. I thought I was a genius for getting a stubby JIS screwdriver for the job. ¯\_(ツ)_/¯

 

[gamefreakgc]

There is also a very tiny bolt at the bottom of the throttle return spring where the two metal faces contact to close the throttle valve. This can be removed with a small 8mm wrench. Once it is out, there's a paint mark showing the position of the threaded rod set by the factory to adjust idle speed. I backed mine out about 1/2 a turn and it raised my idle by roughly 100 RPM. Not saying you should do this as it is not your issue but there are some manual adjustments that can be made on the throttle body that no one knows about.

In my situation, the fuel injectors and intake I had on was causing the idle speed to drop and the ECU wasn't compensating using the idle air control valve so I allowed more air past the throttle valve instead to raise the RPM back to what it was before. In the winter when it is cold I sometimes have to adjust it back or it'll idle 900 RPM in park.