My engine threw a code (P2138) for the APP Sensor yesterday, but everything I'm seeing in my searches reference the TPS. Are these the same thing?? And if not, will someone PLEASE tell me which I should go with?
I've started working on my own vehicle just this past year, and after having replaced my control arms (Satan's creations!), I'm feeling pretty confident I can do this repair. However, if I'm looking for the wrong thing - that could be a problem.
Thanks for the guidance.

 

Not the Same thing.. (or it'd be labeled the Same thing, right?)

TPS- Throttle Position Sensor

APP- Accelerator Position Sensor.

Go by the code. Get a code scanner and ELM reader and see what's up..

 

The code scanner () is showing the P2138 APP Sensor A/B or 1/2 (Throttle Position (TP) Sensor D/E) Incorrect Voltage Correlation...
"Definition: Code P2138 indicates that with the ignition on the PCM detected the difference between the throttle / pedal position sensor / switch D signal and the throttle / pedal position sensor / switch E signal was great than the maximum allowable vaule."

This is where my confusion is coming in.

 

Ok. So, what it's basically saying is that there is a voltage reference disparity between the TPS (Throttle body) and the APP (Accelerator Pedal Position). What that means is that when you push the throttle down about 20%, the APP should be sending a voltage signal via the PCM to the TPS sensor so that the throttle body itself opens up the butterfly by about the same 20% , because the voltages are off.. In your case, this "matching" of the 20% is not occurring, so it's sending an error code. It could be the TPS, it could be the APP, or it could be a corruption of the PCM between the two.

I'd try to see if there's a TSB associated with this issue for this car. It may help which area to focus on. Either one of the sensors or the software that helps correlate/calibrate it.

 

Surprisingly, I actually followed what you were saying. LOL. .....except for the last part where you mentioned a TSB. Will you tell me what that is?

 

Technical Service Bulletin. It is a series of announcements that show company product issues that aren't a safety hazard enough to be considered a "RECALL", but should be addressed by a dealer at the car's next service inspection or repair. This calibration may be handled at no charge to you regardless of any warranties associated with the car that may have expired.

 

Thank you. It is nearly time for my 120,000 mile check-up, so I will just go ahead and schedule it. I haven't dealt much with dealer repairs - since I can either 1, do them myself... or 2, find the repair available at a much lower price from someone I trust. Will this need to be taken to an actual dealer for them to check the TSB or have it 'reported' as an issue? Also, do you think they will be able to tell me which one of the culprits you mentioned above could be the real problem??... or will they do the "It looks as if they are all bad, and that will be $$$." - when, in truth, it is probably just 1 of the 3?

 

that's hard to determine. I can't think for the dealership techs. You can publicly find a list of all TSBs online for your specific make/model of car. That's the easy part. You can print that list and even show a dealership that it needs to be taken care of. There's no cost on your part.

As for the sensors. Your best bet is to get a good code reader with DTC capabilities and see if they can be cleared. Like I stated, OBDwiz software, an ELM327 OBD interface and some time. All can be found on Amazon.

You can make the repairs yourself. try one sensor at a time, and see what happens. Best you can do, my friend.

 

Thank you for the advice! I'll see what I can find and get this thing started. I'm kind of glad my engine finally gave a code --- because I was about to replace the VTEC Solenoid (having been told by a repair shop that *that* was the issue). I'm thinking now that it's the APP or TPS. <sigh>

 

See this link: DTC Advanced Diagnostics: P2138 4514

 

Thank you for the summary. I've forwarded it on (copy/paste) to my technician friend to see what their input is. I'm hoping there is some possible way to test it and locate the issue without having to go through buying new parts that may not be needed. I have no idea what the A APS1 line short to APP sensor B APS2 line is all about, but hopefully he will.
I'll post again and let you guys know what happens.

Thank you both for the input on what the issue(s) might be. When I drove it this morning, it was just making me bonkers.

One other note..... it doesn't really do any of this (no symptoms) when the cruise is set. Does that give any hints as to which it might be?

 

Well, think about it.. if cruise control is set, then there's no change in voltage between the TPS and APP signals because you're statically set for the exact speed of the cruise control. Your foot is not modulating the pedal, which means your throttle (and plate in the intake manifold) are at one point. This means that no disparity in voltage signal exists, thereby, no CEL light. ..