P2138 - Throttle/Pedal Position Sensor/Switch

The p2138 mite not be related to the other codes I was having, did some research they were saying p0011 and 022 were related to ocvs, I think I caused some damage by not changing my oil in time..anyway I fixed a few things for a few different codes all at once and havnt seen one since so idk if they were related. Thamx for the help tho

Just had my first occurrence of the P2138 code on the way into work this morning. I was slowing to a stop at a light when the car lurched forward just prior to coming to a complete stop...made me think I bumped from behind. I tossed the tranny into neutral and noticed that the tach jumped up to 2000 rpm along with a check engine light and a flashing cruise control light on the dash. I tried blipping the throttle to see if it would kick down the rpm and no response...drats! I immediately hit my flashers and was able to idle my way to a parking lot just off the intersection without any drama. I shut the car off for a few seconds and tried to restart, but it wouldn't catch after ~15 seconds of cranking, so I again shut off the ignition and waited about a minute. This time it kicked right over and settled down to a normal 700 rpm idle, but the check engine and cruise control lights were still on/flashing. My throttle response was back on and I not only made it into work but all the way home w/o any issues.

 

Thanx guys for posting your fixes, I will get some contact cleaner and start with my pedal's connector. Hopefully I will have the same success.

TPS 2006 SUBARU TEST IN OHMSHOLDING THE SENSOR WITH THE DENSO NUMBER FACING UP AND GOING FROM LEFT TO RIGHT ON PIN TERMINALS AFTER TESTING TPS I FIND NOTHING WRONG WITH TPS. WILL CHECK PIN DRAG ON CONNECTOR. HAVE CHECKED THE PIN DRAG OG THE TERMINSALS USING A .033 in spade terminal the drag felt thwe same on all 6 terminals. Terminals tested ok at the connector to the TPS.

 

I removed the intake throttle and found it was carboned up and in need of cleaning/service. I removed the intake throttle body and cleaned carb spray. Looks like brand new, Now there is a gap in the plate when it is in closed position. So lets review the code P1238 $ 10 which says throttle / pedal position sensor Switch D / E voltage correlation. It does not say there is a voltage loss. Reading between the lines the voltage is there and the computer is programmed to read a certain voltage at a certain position of the tps and the throttle intake. There is a certain percentage of tollerance or voltage to be read as a example 1.0v to 1.2 volts , if this voltage is not seen within lets say 5 seconds a code P1238 will set and this is because the throttle plate is sticking. Let me also add that this code is temperature related, The code sets form cold start to warm operating temperatures. The throttle plate is sticking inside the throttle body because of the sludge build up around the inside of the plate. Once the throttle body is serviced/cleaned the plate will move freely without sticking because of the sludge build up in the intake throttle body. I will attach a picture of the throttle place after cleaning ,,This is what is must look like. Do not bend or adjust the plate in any way, just clean the sludge.Bitmap PIN 11 - 2 = OPEN1 - 3 = OPEN1 - 4 = OPEN1 - 5 = .482 K OHM IDLE 1.693 K OHM FULL THROTTLE. SLOWLY MOVE PEDAL TO LOOK FOR OPEN POSITION OR METER TO READ INFINITY.1 - 6 = 1.589K OHMS NO CHANGE WHEN PRESSING ACCELERATOR PEDALPIN 22 - 1 = OPEN2 - 3 = .644 K OHM IDLE POSITION. MOVE ACCELERATOR TO FULL THROTTLE LOOK FOR OPEN IN TPS AS THE PEDAL IS MOVED TO FULL THROTTLE. 2.634K OHM2 - 4 = 2.120 K OHM IDLE. READING GOES FROM K OHMS TO 117.1 OHMS AS ACCELERATOR PEDAL IS PUSHED TO FULL THROTTLE.2 - 5 = OPEN2 - 6 = OPENPIN 33 - 1 = OPEN3 - 2 = .644 K OHM IDLE POSITION. MOVE ACCELERATOR TO FULL THROTTLE LOOK FOR OPEN IN TPS AS THE PEDAL IS MOVED TO FULL THROTTLE. 2.634K OHM. THE READING IS THE SAME AS 2 - 3 WITH THE LEADS ON OPPOSITE POLES AS 2 - 3. 3 - 4 = 2.522K OHM NO CHANGE WHEN SWEEPING THE ACCELERATOR PEDAL3 - 5 = OPEN3 - 6 = OPENPIN 44 - 1 = OPEN4 - 2 = 2.120 K OHM IDLE. READING GOES FROM K OHMS TO 117.1 OHMS AS ACCELERATOR PEDAL IS PUSHED TO FULL THROTTLE.4 - 3 = 2.521K OHMS WITH NO CHANGE OF READING WITH SWEEP OF ACCELERATOR PEDAL4 - 5 = OPEN4 - 6 = OPENPIN 55 - 1 = .484K OHMS. 1.695 AT FULL THROTTLE POSITION. LOOK FOR OPEN AS THE PEDAL IS SWEPT TO FULL THROTTLE. 5 - 2 = OPEN5 - 3 = OPEN5 - 4 = OPEN5 - 6 = 1.372K OHMS AT IDLE. LOOKING FOR OPEN AS PEDAL IS SWEPT TO FULL THROTTLE. 132.0 OHMS AS THE THROTTLE PEDAL IS SWEPT TO FULL THROTTLE.PIN 6 6 - 1 = 1.589K OHMS NO CHANGE WHEN SWEEPING THE ACCELERATOR PEDAL 6 - 2 = OPEN6 - 3 = OPEN6 - 4 = OPEN6 - 5 = 1.382K OHMS AT IDLE, SWEEPING THE ACCELERATOR PEDAL TO FULL THROTTLE LOOKING FOR OPEN , 117.6 OHMS AT FULL THROTTLE.

I've been having this code off and on for a couple months now, and everytime I get it the gas pedal is unresponsive of course, and the only way I've found to make it work is by unplugging the maf. Then I plug it back up a day or so later and it will be fine for awhile but it's gotten worse recently.. What are you guys doing on the road to get the pedal working? I understand cleaning the connections but can't exactly do that on the highway. Also does maf have anything to do with the problem? I wonder if it could be bad...

just turning off the engine and restarting a few min later..

 

the maf should have nothing to do with it.

 

for instance if you have it unplugged and the car still disabled the throttle that will prove it.

 

as i said in early posts i only had luck with cleaning the area under the cover of the throttle plate

Agreed, turning off the car and waiting a few minutes should clear the code. There is a set amount of time or a set number of starts (3?) that will clear the code if the issue doesn't repeat itself.

 

Nothing to do with MAF.

 

You can reach the connector on the pedal assemble, unplug and replug it pretty easily. If that's where your problem is, it should keep the problem from reappearing for a while (repeats every few years for me).

I understand restarting a few times but it has gotten so bad recently that it doesn't ever go off.. Only way I can drive is to unplug the maf which would run everything at a preset level right? I don't think the maf is bad, it's just the only way I can drive now is by unplugging it..

I found a pedal assembly at the junkyard for $45 but don't wanna fix something if it ain't broke. Do you know if the nonturbo legacy has the same pedal assembly?

^ pedal should be the same..

 

 

i'm 99% sure its not the pedal its self.

 

but you just unplug your maf and the throttle works fine? and has never acted up with the maf unplugged?

Never acted up with maf unplugged... I think it runs a basic map when it's unplugged since it has no idea how much air is coming in, just guesses how much fuel to give it(least that's my understanding) I don't know how relevant that is to the gas pedal but it works to get the pedal working again..

 

Anyway I cleaned the connections again on the pedal and throttle body, and plugged maf back up, and havnt seen the code in a couple days. I feel like everything is just a temporary fix, and I'm not certain buying a new pedal would fix it either.

Never acted up with maf unplugged... I think it runs a basic map when it's unplugged since it has no idea how much air is coming in, just guesses how much fuel to give it(least that's my understanding) I don't know how relevant that is to the gas pedal but it works to get the pedal working again..

 

Anyway I cleaned the connections again on the pedal and throttle body, and plugged maf back up, and havnt seen the code in a couple days. I feel like everything is just a temporary fix, and I'm not certain buying a new pedal would fix it either.

 

 

the maf unplugged does run a speed density fuel map using the map sensor. but tat has nothing to do with the drive by wire system.

 

it could have something to do if there is an electrical short some where associated with the maf that is carrying through the system.

 

because the drive by wire pedal and throttle servo have 2 position sensors each . they are monitored by the ecm and if one of then is not where its supposed to be it will disable the throttle and set the code as your seeing.

^This exactly! It's just telling you the two redudent sensors aren't agreeing. Since it's happening so much, you can hook up a cable and laptop and use freessm to monitor both sensors.

^ free ssm doesnt realy tell you both .. it tells you the pedal angel and the throttle plate angel. but each device has two sensors. and it doesnt tell you each sensor only the result of the ecm's calculation from the two sensors per unit.

 

and the throttle plate is based on requeste throttle map and another one for the calculation

so the pedal angle and the throttle body are not always the same.

Thanks for the clearification. I thought that I had seen somewhere a plot where someone showed the 'blip' that caused the P2138 code to get set. I think I misinterpreted that. But either way, it would be good to get traces of throttle plate angle and pedal angle when the code is set.

 

Here is a link with the FSM troubleshooting steps for P2138: http://forums.nasioc.com/forums/showthread.php?t=803788

Well the code came back again. I have cleaned the connections multiple times. How do I clean the tb can I just take off the fmic pipe and spray some sht in the tb? If that doesn't work I guess I will buy a new pedal assembly.

From: http://www.iwsti.com/forums/ecu-tuning-performance-electronics/200004-possible-throttle-position-sensor-problem-surge-effect-while-crusing-2.html

 

"They gave me some Subaru "Throttle Plate & Induction Cleaner" and told me to take shop rags and pull off the TMIC.

 

Once the TMIC was removed, there's a little flapper - or - butterfly valve in the throttle body. I sprayed the piss out of it and took shop rags and wiped all over the inside and each side of the flapper."

^ lol what a waste of time ..

 

you need to take the throttle body off and and take the clips off the side cover.. clean under that cover.

 

the sensor is actually part of the cover.. you could clean the butterfly with a sand blast untill there is nothing left and it will still function the same.

 

don't change the pedal assembly because its not the problem ..

Several people report success after replacing the pedal assembly. Why do you think that's not the problem? Because of the connection with the MAF?

well there is no wearing parts in the pedal

 

and the maf thing realy boggles my mind ..

 

i had this issue and my maf doesnt do anything since i have a buick engine..

^ you could test the pedal if you remove it and check each circuit with a analog ohm meter.

It is my understanding that there are two sensors down by the pedal that are redundant. When they disagree, it throws this code. If one of those sensors has a flat spot, replacing the pedal will resolve the code.

 

FSM troubleshoot steps have you looking at the pedal assembly or the harness to the ECM or the voltage supply to the pedal. Can't see where it could be anywhere else. For some reason dealers like replacing the throttle body sensor, but I don't see why. This code has nothing to do with that.

the sensors are magnetic not a carbon brush on a slide.

 

there are two sensors in the pedal and two in the throttle body.

 

mine simply had metal shavings on it from the servo gear

 

this code blankets both the pedal and the throttle

 

you can invoke the code by grounding one of the pins at the throttle body. and at the pedal.

Edited January 21, 2014 by frank_ster

Ty all for the thread info here.

Had the described issue myself ~ 1 mo ago (shutting down at cruise, unresponsive pedal...etc)... including on a busy 1 lane bridge (facepalm...). I am running an Access Port V3 so I was always able to set off again after a quick ECU reset, however the problem would consistently return every 4ish days. Presumably that is about the length of time for the readiness monitors to indicate a "fail" in the throttle system.

 

Hit the contacts both pedal and TB side with liberal amounts of cleaner. Also hosed and scrubbed the crap out of the TB with carb cleaner. Note: Recommendation to anyone looking to do this, I have personally experienced/been privy to TB failure from messing with the butterfly too much on these ethrottle cars (Sentra, both 1.8 and 2.5L). Suggest moving it slowly and as little as possible for cleaning. I opened mine up wide, and held it there for the entire duration of the scrub down.

 

Approx 3 weeks later, issue has not returned. Back to confident highspeed passes!

 

My $0.02, that is all. Cheers,

So cleaning the throttle body fixed yours as well as it fixed mine

 

PS 2006 SUBARU TEST IN OHMSHOLDING THE SENSOR WITH THE DENSO NUMBER FACING UP AND GOING FROM LEFT TO RIGHT ON PIN TERMINALS AFTER TESTING TPS I FIND NOTHING WRONG WITH TPS. WILL CHECK PIN DRAG ON CONNECTOR. HAVE CHECKED THE PIN DRAG OG THE TERMINSALS USING A .033 in spade terminal the drag felt thwe same on all 6 terminals. Terminals tested ok at the connector to the TPS.

 

I removed the intake throttle and found it was carboned up and in need of cleaning/service. I removed the intake throttle body and cleaned carb spray. Looks like brand new, Now there is a gap in the plate when it is in closed position. So lets review the code P1238 $ 10 which says throttle / pedal position sensor Switch D / E voltage correlation. It does not say there is a voltage loss. Reading between the lines the voltage is there and the computer is programmed to read a certain voltage at a certain position of the tps and the throttle intake. There is a certain percentage of tollerance or voltage to be read as a example 1.0v to 1.2 volts , if this voltage is not seen within lets say 5 seconds a code P1238 will set and this is because the throttle plate is sticking. Let me also add that this code is temperature related, The code sets form cold start to warm operating temperatures. The throttle plate is sticking inside the throttle body because of the sludge build up around the inside of the plate. Once the throttle body is serviced/cleaned the plate will move freely without sticking because of the sludge build up in the intake throttle body. I will attach a picture of the throttle place after cleaning ,,This is what is must look like. Do not bend or adjust the plate in any way, just clean the sludge.Bitmap PIN 11 - 2 = OPEN1 - 3 = OPEN1 - 4 = OPEN1 - 5 = .482 K OHM IDLE 1.693 K OHM FULL THROTTLE. SLOWLY MOVE PEDAL TO LOOK FOR OPEN POSITION OR METER TO READ INFINITY.1 - 6 = 1.589K OHMS NO CHANGE WHEN PRESSING ACCELERATOR PEDALPIN 22 - 1 = OPEN2 - 3 = .644 K OHM IDLE POSITION. MOVE ACCELERATOR TO FULL THROTTLE LOOK FOR OPEN IN TPS AS THE PEDAL IS MOVED TO FULL THROTTLE. 2.634K OHM2 - 4 = 2.120 K OHM IDLE. READING GOES FROM K OHMS TO 117.1 OHMS AS ACCELERATOR PEDAL IS PUSHED TO FULL THROTTLE.2 - 5 = OPEN2 - 6 = OPENPIN 33 - 1 = OPEN3 - 2 = .644 K OHM IDLE POSITION. MOVE ACCELERATOR TO FULL THROTTLE LOOK FOR OPEN IN TPS AS THE PEDAL IS MOVED TO FULL THROTTLE. 2.634K OHM. THE READING IS THE SAME AS 2 - 3 WITH THE LEADS ON OPPOSITE POLES AS 2 - 3. 3 - 4 = 2.522K OHM NO CHANGE WHEN SWEEPING THE ACCELERATOR PEDAL3 - 5 = OPEN3 - 6 = OPENPIN 44 - 1 = OPEN4 - 2 = 2.120 K OHM IDLE. READING GOES FROM K OHMS TO 117.1 OHMS AS ACCELERATOR PEDAL IS PUSHED TO FULL THROTTLE.4 - 3 = 2.521K OHMS WITH NO CHANGE OF READING WITH SWEEP OF ACCELERATOR PEDAL4 - 5 = OPEN4 - 6 = OPENPIN 55 - 1 = .484K OHMS. 1.695 AT FULL THROTTLE POSITION. LOOK FOR OPEN AS THE PEDAL IS SWEPT TO FULL THROTTLE. 5 - 2 = OPEN5 - 3 = OPEN5 - 4 = OPEN5 - 6 = 1.372K OHMS AT IDLE. LOOKING FOR OPEN AS PEDAL IS SWEPT TO FULL THROTTLE. 132.0 OHMS AS THE THROTTLE PEDAL IS SWEPT TO FULL THROTTLE.PIN 6 6 - 1 = 1.589K OHMS NO CHANGE WHEN SWEEPING THE ACCELERATOR PEDAL 6 - 2 = OPEN6 - 3 = OPEN6 - 4 = OPEN6 - 5 = 1.382K OHMS AT IDLE, SWEEPING THE ACCELERATOR PEDAL TO FULL THROTTLE LOOKING FOR OPEN , 117.6 OHMS AT FULL THROTTLE.

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Good job taka

The drive by wire system just have 2 sensors in each part and they both have to be be saying the same thing.

 

Also FYI cleaning the throttle plate on the inside is for the birds

 

Just remove the plastic cap on the side and clean that