Check Engine Light No Power Weak Car Acceleration - Code P2138

Do you have a check engine light on and you have a APP Code, a P2138? That's what we're going to talk about in this video.

Now, what the APP sensor is is the accelerator pedal position sensor, which in other words, it's your gas pedal. On this pedal, there is a sensor, and that sensor is gonna send a signal to the engine's computer, basically the brain of the vehicle. And as you step on that pedal, it's going to tell the computer what you want the car to do. Now, when you have this condition, you're gonna get a check engine light, and you may also get an engine reduced power light come on your dash. The reason why you get an engine reduced power light on is because the computer isn't exactly sure that everything that you're telling the pedal to do is accurate. Basically, it's the computer in safe mode, and it's going to reduce heavy acceleration and fast speeds. Now, what could be wrong if you get this code is something wrong with the sensor, something wrong with the connector, not making a good connection, something wrong with the wiring, or also something wrong with the computer.

So, this gas pedal actually has two sensors in it. And the reason they do that is pretty much a fail-safe just in case one of the sensors isn't reading properly, which is pretty much the case that we have right now. Now, these sensors are not going to be at the exact same spot. They need to agree with each other and there's going to be a range that these sensors have to be within. So, right off the bat, this one's at 19% and this one's at 9%, which is where it's supposed to be. But if you step on the accelerator, you can see, they both go up. And it's hard to tell with this code reader, you can't tell exactly what's going on. What you don't want to see is a spike. Like if you go half throttle and you notice that one of the sensors goes to 100% or goes to 0%, that's what we're looking for as we're checking this. So, what you want to do as you're watching the graphs, if you very lightly step on the gas pedal and you just want to make sure you don't see anything spike either up or down. And right now, everything's pretty smooth. If you do see a spike, then there's a spot in the accelerator pedal itself that's either dirty or the contact's bad, and that's what's causing the code. In that case, the pedal itself would need to be replaced.

With other types of scan tools, you may be able to select a setting called agree or disagree for the accelerator pedal position. And then if you notice that it's disagree right off the bat, that's good, you can wiggle the wires and see if that changes, or if you step on the accelerator and it changes too, that's a good indication that it's probably in the pedal itself and not the wires. So, here's the connector right here. And you can look at the wires and just make sure you don't see anything frayed. You can be watching the bar graph or the line graph on the scan tool while you're wiggling these and see if you see anything change then. That's a good indication it's a wire or a connector. Make sure the connector is tight. Just give it a wiggle. You can pull the connector off. There's a little lock on there on this one. Slide the connector off, and then just look down. See if you see any corrosion in the terminals and they all look pretty good. See if any of these wires seem frayed, or if any of these wires seem loose, if you could just pull them out of the connector itself, and that's not good.

So, this sensor uses low voltage to send the signal to the computer. Basically, it's not going to be 12 volts, it's a 5-volt system. So, if you saw dielectric grease on here, it could potentially be the wrong dielectric grease. You need to use dielectric grease for low voltage. You can't just use any type of dielectric grease.

Next, week can test the wires with an actual meter. How we want to test the wire if it's good is put the meter on the ohms reading, it looks like a little horseshoe. Then I'll turn the beep on so that when the terminals are touching, you get a little beep. So, how this works is the meter actually sends a little bit of voltage down one side of the lead and this other lead is actually gonna read that voltage. So, when it touches, it sees that reading and you get a beep. So, we're gonna put one lead on one side of the wire and then we can test it with the other side. And we know that there's continuity through that wire. Basically, the wire is good. You can actually see what the wire is reading, what the amount of resistance that wire is, which that's really good. If we put the leads together, it's going to be very close to that. About 0.3 or 0.4, which is the same as the wire. Now, with the wire all good, if I cut the wire, it's gonna stop. That's basically what we're testing, to see if there's a break in the wire.

Now, what I want to do is actually take this cover off this connector before I test it. I don't want to take my lead from my meter and push it through any of these slots right here. Then you spread the cover and then possibly ruin the terminals, which if you just take a small flat blade tool and just slide the cover off just like that. With the cover up, I can actually just take the test lead and just touch one of the terminals without...because you don't want to spread any of those terminals. If you push it in there, then you're going to ruin the terminals for the connector. The terminals are basically what may contact with the pedal terminals on the inside there.

So, I have my test meter with one of the test leads on a ground. You can double-check that. Just touch another piece of metal just make sure that's good. Now, you want to do this test with the ignition off with basically the key out of the ignition. And we're going to test the purple wire and just lightly touch the purple wire, and that's good. You want to make sure that it is at least less than 5 ohms, which it is way less, you're at 0.4. And then same with the brown one, do the same. And that's very close. Now, if you were testing this and one of these was extremely higher than the other, even though it's within spec, if you had one that was 4.0 and then you had one that was 0.4, that would be significant. There would be a significant difference and you're gonna want to check out that circuit. There might be something wrong with one of those wires.

Next, we're going to switch our meter to voltage, which is DC voltage. We want to check the voltage of the other two circuits that are concerned to us. Now, when we do this test, we actually want to turn the key in the on position. Don't start the vehicle. Circuits we want to test is the black and white wire. So, it's a white wire with a black stripe. Just lightly touch that. My other lead is still on a ground, and it's at 4.98, which is good. It needs to be over 4.8. And we'll do another test on the tan wire, same test. And that tested 4.9, which that's over 4.8. Now, if you notice that they're both below voltage, double-check your battery voltage, you want your battery to be at least 12 volts when you're testing this system. If it's not 12 volts, you're gonna want to charge it up. And then same as the other wire test, if you see that one of these tests significantly different than another one, you're gonna want to look into that wire. See if there's a break somewhere in the wire between here and the computer or the PCM, power control module. So, we didn't see anything wrong with the connector or with the wires, so in our case, we're actually gonna have to replace the accelerator pedal itself.

So, whether you replace the accelerator pedal or replace the connector or repair those wires, after you do that, you clear the code, you should be good to go. If you enjoy this video, make sure you subscribe to our channel, ring that bell, and turn on all notifications so you don't miss any of our videos.

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