My wife is a gremlin.

The car is throwing the OBD code P1120/P1121 for Accel Position Sensor Circuit - Range/Performance problem.

First, I guess I didn't know there was an accelerator circuit. I thought the gas pedal pulled on a cable which let more or less gas through to the engine. Maybe not so much for fuel injected, computer controlled engines?

Any help what this is, how to replace (easy for non-handy person w/out sophisticated tools), parts involved? I'll do some searching but any hands-on experience based insights appreciated.

If beyond novice level, how much is something like this to fix in a shop?

ETA: Doh - yes, this is a Lexus - 2000 GS300. Wife has been driving this car (which has not had issues) while I drove her car (the ES300 w/ the fixed ignition coil issue) until we get money to buy a new car. The car seems to recover a bit after turning it on/off. I limped along for a few miles (pedal to the metal but only going about 30mph). But then I stopped, turned off the car for a few minutes, restarted, and it was fine for the drive home (another few miles).

I can't see where the throttle cable goes. Engine was hot so didn't poke around much. There is an engine cover - I'll remove that tomorrow morning and take a peek.

1) Cable is not too loose or tight
2) DVM the Accel Position Sensor and the throttle position sensor for 5V (WOT = wide open throttle? Can I check this with the engine off but the ignition in On mode? Or does the engine have to be running?
3) Check and unplog throttle connectors

This message has been edited. Last edited by: konata88,

What car/truck? Year?

Toyota?

Is this the Lexus? If so, was the upper intake manifold removed when the ignition issues were corrected?

I'd first check the connector/connectors at the throttle body. Unplug, check for any obvious damage to the pins and sockets. Plug connectors back in, clear codes and drive vehicle to see if the codes come back.

quote:

First, I guess I didn't know there was an accelerator circuit. I thought the gas pedal pulled on a cable which let more or less gas through to the engine.

Cable throttles haven't been used since the early 2000s. They are all now throttle by wire.

Throttle position sensor usually sits on the throttle body. It may or may not be a serviceable part separate from the throttle body.

quote:

Originally posted by konata88:
My wife is a gremlin.

The car is throwing the OBD code P1120/P1121 for Accel Position Sensor Circuit - Range/Performance problem.

First, I guess I didn't know there was an accelerator circuit. I thought the gas pedal pulled on a cable which let more or less gas through to the engine. Maybe not so much for fuel injected, computer controlled engines?

Any help what this is, how to replace (easy for non-handy person w/out sophisticated tools), parts involved? I'll do some searching but any hands-on experience based insights appreciated.

If beyond novice level, how much is something like this to fix in a shop?

Definitely need to know the vehicle and yes, current auto electronics suck.

My father has had 2 Ford PSD’s with a code that sounded a lot like that and it turned out to be a little PoS sensor that was relaying the accelerator pedal position to the brain, this is part of the “drive by wire” bullshit that all manufacturers use now (I think) so it’s not isolated to any one make.

I have no idea if this is your issue or not but if it is, it’s a pretty easy fix.

If your car has a throttle position sensor it should be about $30 and two screws held in using a number 20 Torx bit.

If it is something newer than that, it may have an electronically controlled throttle similar to 'drive by wire'. Then you have to call NASA or shoot it with a 10mm if you don't have any extra BMG rounds.

quote:

Originally posted by egregore:

quote:

First, I guess I didn't know there was an accelerator circuit. I thought the gas pedal pulled on a cable which let more or less gas through to the engine.

Cable throttles haven't been used since the early 2000s. They are all now throttle by wire.

If this is the Lexus, it very well might have a cable. My 1998 LS400 uses a cable, but uses both sensors so the ECM can close the throttle if the VSC system commands it.

If the upper intake was removed to replace the ignition items from his earlier issues, it's possible that the cable is too tight causing the throttle to be opened slightly. This will give an incorrect throttle position value to the ECM, thereby throwing the codes.

I suspect that the vehicle is still drivable and won't go into a limp home mode. That will happen on a full fly-by-wire system.

To check the system a DVOM and/or graphing scanner is usually used. The sensors are usually read transversely from each other. This means one sensor will read from 0 volts up to usually 5 volts at WOT, while the other will read from 5 volts down to 0 volts at WOT. It's when these readings don't correlate that the codes are set.

(It can have a cable and a TPS.)

ETA: Doh - yes, this is a Lexus - 2000 GS300. Wife has been driving this car (which has not had issues) while I drove her car (the ES300 w/ the fixed ignition coil issue) until we get money to buy a new car. The car seems to recover a bit after turning it on/off. I limped along for a few miles (pedal to the metal but only going about 30mph). But then I stopped, turned off the car for a few minutes, restarted, and it was fine for the drive home (another few miles).

I can't see where the throttle cable goes. Engine was hot so didn't poke around much. There is an engine cover - I'll remove that tomorrow morning and take a peek.

1) Cable is not too loose or tight
2) DVM the Accel Position Sensor and the throttle position sensor for 5V (WOT = wide open throttle? Can I check this with the engine off but the ignition in On mode? Or does the engine have to be running?
3) Check and unplog throttle connectors

quote:

Originally posted by konata88:
ETA: Doh - yes, this is a Lexus - 2000 GS300. Wife has been driving this car (which has not had issues) while I drove her car (the ES300 w/ the fixed ignition coil issue) until we get money to buy a new car. The car seems to recover a bit after turning it on/off. I limped along for a few miles (pedal to the metal but only going about 30mph). But then I stopped, turned off the car for a few minutes, restarted, and it was fine for the drive home (another few miles).

I can't see where the throttle cable goes. Engine was hot so didn't poke around much. There is an engine cover - I'll remove that tomorrow morning and take a peek.

1) Cable is not too loose or tight
2) DVM the Accel Position Sensor and the throttle position sensor for 5V (WOT = wide open throttle? Can I check this with the engine off but the ignition in On mode? Or does the engine have to be running?
3) Check and unplog throttle connectors

There is one sensor assembly on the throttle body that has both sensors. According to Alldata, both will sweep from 0-5 volts.

You check with the Key On Engine Off, KOEO.

The connector on the throttle body will have 4 wires, blue, blue-yellow, blue-red and brown. The signal wires should be blue and blue-red. According to Alldata, the readings from both should read the same voltage from closed throttle up to WOT. If they don't concur, then the sensor is bad.

To properly check for concurrence, you'll need two DVOMs or a graphing scanner.

First, I'd disconnect the connector and using the DVOM check between the brown wire and the blue-yellow wire for 5 volts with the KOEO, back probe the wires though. If you have 5 Volts, then the ground and power circuits from the ECM are good.

Next I would plug the connector back up and using a single DVOM, back probe either the blue wire or the blue-red with the red lead. Hook the black lead to battery ground, then slowly open the throttle and watch the reading, it should climb smoothly and steadily up to 5 volts. If it doesn't climb or it drops out along the way, then you have found an issue. Do this same check on the other wire you didn't check. But to check both at the same time, you will need two DVOMs.

Wow!! Awesome! Thanks SB. Fantastic instructions.

I only have one DVOM so checking for concurrence may be difficult. But at least I can check for function singularly.

I'll try to find the throttle body tomorrow. I may need to go buy thin probes - I'm not sure if the stock probes are thin enough. Or maybe I can use some short pieces of wire to help with back probe.

I found some pics online of a generic throttle body. Not sure exactly where it's located but I'll try to find it - can't be that hard.

quote:

Originally posted by konata88:
Wow!! Awesome! Thanks SB. Fantastic instructions.

I only have one DVOM so checking for concurrence may be difficult. But at least I can check for function singularly.

I'll try to find the throttle body tomorrow. I may need to go buy thin probes - I'm not sure if the stock probes are thin enough. Or maybe I can use some short pieces of wire to help with back probe.

I found some pics online of a generic throttle body. Not sure exactly where it's located but I'll try to find it - can't be that hard.

T-pins work great for back probing.

Just follow the tube from the air cleaner to the intake manifold, there's the throttle body.

I checked for 5V between the brown and blue-yellow; it was reading about 4.8V. I assume that's close enough - good to go?

I'm running into problems with checking 5V for the signal wires. I can't back probe because the wires are sealed. Can I poke through the insulation using a pin (sewing pin?).

BTW, I broke the part off the connector that locks it in place. It's a pretty snug fit but I guess it could come loose while driving. Am I going to want to have the connector replaced urgently? Or next oil change?

I stuffed in some thin gauge wire into the connector. I think I was able to take some readings. DVOM black was touching the battery black nub.

Blue wire 0.5 - 3.1v
Blue-red wire 2.2 - 5v

So, if these readings are correct, something broken?

quote:

Originally posted by konata88:
I stuffed in some thin gauge wire into the connector. I think I was able to take some readings. DVOM black was touching the battery black nub.

Blue wire 0.5 - 3.1v
Blue-red wire 2.2 - 5v

So, if these readings are correct, something broken?

Looks like there is issues with both sensors. Based off of these readings, I think it's safe to say that a replacement is needed. But just like building a house, measure twice cut once. Might be worth checking again. You can back probe along the wire into the sealed part with the T-pin. Don't poke holes in the insulation if possible. If you do, seal them with some silicone sealant.

As far as the connector, I would get a new one. One trick that can be done is to put some silicone sealant in the outer ring of the connector to keep it in place until a new one can be obtained.

Thanks for your help SB.

Okay, I'll go out and buy some T pins and check again.

So, there are two sensors inside the black thing with the coil spring? One is called the Throttle Position Sensor and the other is called the Accelerator Pedal Position Sensor?

Or is one inside and there is another sensor elsewhere? Just trying to figure out what parts I need to buy if the voltages are still bad after using the T pin.

Is this the only part I need for both sensors? Same part - two different sources.

https://www.partsgeek.com/lk5p...or-pedal-sensor.html

https://www.lexuspartsnow.com/...ection-system,,22060

Both sensors are in the same assembly. That's why you are checking two signal wires not one. I'd go with the Lexus part if and when you order.

I believe that this is held in place by phillips head screws, so use a good screwdriver when removing.

One trick I use to remove such screws is to keep counter-clockwise force on the screwdriver while tapping the head of the screwdriver with a hammer. This helps jar it loose while reducing the chances of stripping the head.

The solder joints are cracked inside the TPS.

I've had to make this repair on one myself.