P2138 code and intermittent limp mode!

G

Gtstorey

Goblin Guru
Robinjo said:
APP Jumper Harness. It connects the wiring harness to the Accelerator Pedal. I assume the wring was generic between Cobalts (and other GM models) as was the ACC Pedal. Then, all the needed was a 'jumper harness' to correct the wiring outputs. Everything basically makes an X to the other side. These were used in at least LSJ vehicles, do the other models not require this?
Click to expand...
Mine may have this, I don't remember. It can only help to remove it, if you get the wiring correct, and make the connections correctly.
 
Robinjo

Robinjo

Goblin Guru
Joebob said:
It seems other models do not have the jumper harness. Mine as a SS/NA was straight to the wire harness. Have you checked the jumper for wiring issues?

Joe
Click to expand...
I have, I replaced it actually. After the APP and TB didn’t fix the issue I started there. It was easy and cheap(ish).
 
C

Chubbs

Well-Known Member
Did some more troubleshooting, but I unfortunately don't know if the results I got are expected or not.

I probed the whole system while everything is connected, and the car on. Both sensors (on the pedal, wt/black and tan wires) have a solid 5.03 volt reference.

The signal output from the pedal is a bit strange though. The dark blue wire is 1.080 volts at idle, and 4.3 volts at wide open throttle. The light blue wire for the other sensor is 4.3 volts at idle, and about 2.7 at wide open throttle. Obviously that side seems a bit suspicious, 4.3 to 2.7 is sort of an odd range. It's also inverted of the other side, but maybe that's normal.

Does anyone know what a normal voltage reading should be off of these sensors?
 
G

Gtstorey

Goblin Guru
I sort of think the voltage should match though. I don’t know which is correct or even if they should always match.
 
C

Chubbs

Well-Known Member
My values were slightly different, but consistent with the article. Since I have already replaced the pedal with no effect, I didn't really suspect the pedal was the problem anyway. Good article though.


Gtstorey said:
While the basic functions and test steps are probably the same from the 2.2 to the SC, the actual values given in the test may be different. I can’t actually get rid of the pop ups enough on my phone to actually read it.
Click to expand...
 
C

Chubbs

Well-Known Member
I think I have my answer, I just wasn't ready to admit it. I have shorts to ground on three of the six wires that should not have any continuity to ground. The resistance is in the mega ohms, but it's not infinite, and I can change the value by yanking the wire harness around. I'm pretty sure I have an intermittent short somewhere.

I'm going to use Joe Bob's method of running a new wire bundle down the center tunnel. It's not the solution I wanted, but I think that's where I'm at. I have eliminated the pedal, and I doubt two throttle bodies are wrong. The only other item in the mix is the PCM, and it's never the PCM.

I've got the wire fishing fiberglass rod on the way, and six conductor cable. I'll let you guys know if it solves my issue.
 
Robinjo

Robinjo

Goblin Guru
Joebob, can that pedal test be performed with the pedal out of the vehicle? It’d be a lot easier on a bench rather than in the Goblin.

Edit: just answered my own question by testing my old APP assembly on the bench.
Answer is yes, you can…. My old unit passes the test. Time to pull my new one from the car.

Edit 2: my new unit passes as well but I get closer to the description numbers with the old unit. Going to try this one moving forward.
 
Last edited:
C

Chubbs

Well-Known Member
Robinjo said:
Joebob, can that pedal test be performed with the pedal out of the vehicle? It’d be a lot easier on a bench rather than in the Goblin.
Click to expand...
Yes, that's how I did it just now. Your probing the connector on the pedal itself, so you have to disconnect the connector anyway. Might as well pull it out of the vehicle. It's pretty easy to do on the bench.
 
G

Gtstorey

Goblin Guru
The service manual for the later models has a different test procedure for the 2.2 & 2.4.
In addition the P2138 is an indicator of high resistance in one of the APP circuits.
 

Attachments

Joebob

Joebob

Goblin Guru
Yes, because of your Jumper connector, your pin outs will be different, but I could not find an LSJ procedure. Maybe with the jumper attached it would line up.

Like for me in the past and others have checke, it has not been the pedal assembly that is causing the issue but the modified wiring or connectors.

Joe
 
Robinjo

Robinjo

Goblin Guru
Ah ok, I wanted to be clear on what was being posted. I wasn't completely sure if it was us or others. Good looking out for others that may need this in the future.

My Values from the bench testing:
New APP Unit (static/pedal pressed)
Test #1: 1.51 / X
Test #2: 2.35 / 1.62
Test #3: 2.23 / X
Test #4: 2.94 / 2.73

Old APP Unit (static/Pedal pressed)
Test #1: 1.48 / X
Test #2: 2.69 / 1.74
Test #3: 2.16 / X
Test #4: 3.10 / 2.82
 
Last edited:
G

Gtstorey

Goblin Guru
Part numbers do seem to cross reference for APP for all models except TC. So I think the procedure I posted above will likely work for all models other than the TC. You still might have to determine the correct terminals. This is probably why the SC has the jumper harness.
 
Robinjo

Robinjo

Goblin Guru
I tested right to the APP terminal, not through the jumper harness. The output on the APP should be standard across, right? Then the jumper makes the wiring from the ECU work out properly. Unless I'm thinking this all wrong. I thinking out loud here, so if any of this is wrong then let me know.
I could check part numbers across a few different early models to see if they are the same...... Edit: you already did that.

Gtstorey said:
Part numbers do seem to cross reference for APP for all models except TC. So I think the procedure I posted above will likely work for all models other than the TC. You still might have to determine the correct terminals. This is probably why the SC has the jumper harness.
Click to expand...
Does the newer model with the potentiometer sensors still have the 6-pin connectors on the APP? Is that only used on the TC models?
 
You must log in or register to reply here.
Top