P2138 After replacing Throttle Body and Throttle Pedal

[AllTerrain1025]

My daughter recently got an original owner 2012 Nox with 192K miles on it. It started doing the reduced engine power / service Stabilitrak accompanied by a P2138 code. I replaced both the gas pedal and throttle body thinking that doing both sides of the signal would fix the issue. Took it on a test drive and it keeps throwing the same code.

The original owner had a ton of service records and the one thing I did not see being done was the timing chain. It does sound like there is starting to be some slap from it when it is idling, along with a bit of a lumpy idle. When she first got the vehicle I replaced the high pressure fuel pump, plugs, and coils as part of a major tune up.

What are everyone's thoughts? I know the timing chain is on the menu, but I do not see why that would cause a P2138 to keep showing up. Are there any other parts besides the pedal and throttle body that could close the loop on that code that I am not thinking of?

Any help is appreciated.

 

[Hey Vern!]

from kelly blue book
One of the first causes of the P2138 code is a defective ECM. Circuit problems, such as spoiled or corroded wires or faulty connections, can also cause the issue. You will often find that a defective throttle position sensor can cause the code to set. A damaged throttle body will also lead to the ECM setting of the P2138 code and damaged wiring or sensors of the accelerator pedal. These are leading causes of the issue because they inhibit the ECM from gathering and correlating the voltages to keep the vehicle operating as it should. Finally, the ECM may need a software update if it’s not working normally, or you may need to replace the ECM altogether in rarer cases.

 

[AllTerrain1025]

from kelly blue book
One of the first causes of the P2138 code is a defective ECM. Circuit problems, such as spoiled or corroded wires or faulty connections, can also cause the issue. You will often find that a defective throttle position sensor can cause the code to set. A damaged throttle body will also lead to the ECM setting of the P2138 code and damaged wiring or sensors of the accelerator pedal. These are leading causes of the issue because they inhibit the ECM from gathering and correlating the voltages to keep the vehicle operating as it should. Finally, the ECM may need a software update if it’s not working normally, or you may need to replace the ECM altogether in rarer cases.

I replaced the throttle body and the accelerator pedal and the code is still popping up. Would the next best step be to have a dealer update the ECM?

 

[maxpg]

There are only two repair procedures for P2138 in the manual:
 Accelerator Pedal with Position Sensor Assembly Replacement
 Control Module References for ECM replacement, programming, and setup

And two pages of exercises with a scan tool and multimeter on how to verify between two.

 

[AllTerrain1025]

There are only two repair procedures for P2138 in the manual:
 Accelerator Pedal with Position Sensor Assembly Replacement
 Control Module References for ECM replacement, programming, and setup

And two pages of exercises with a scan tool and multimeter on how to verify between two.

Well, since I already replaced the Accelerator Pedal, then next step would be to look at the ECM I guess. Can you share that info on how to check the ECM?

 

[maxpg]

Sure:
DIAGNOSTIC AIDS
 If a shared 5 V reference circuit is shorted to ground or shorted to a voltage, other 5 V reference circuits
may be affected.
 The scan tool 5 V reference parameter should display between 4.8-5.2 V.
 A high resistance condition on the accelerator pedal position circuits could cause a DTC to set.

CIRCUIT/SYSTEM VERIFICATION
1. Ignition ON, observe the DTC information with a scan tool. Verify DTCs P0697 or P06A3 are not set.
 If a DTC is set, refer to DTC P0641, P0651, P0697, or P06A3 (ECM) for further diagnosis.
2. Ignition ON, observe the scan tool Accelerator Pedal Position percentage parameter. The scan tool should
display 0 percent.
3. Observe the scan tool APP Sensor 1 and 2 Agree/Disagree parameter while performing the following
tests:
 Rapidly depress the accelerator pedal from the rest position to the wide open throttle position
(WOT) and release pedal. Repeat the procedure several times.
 Slowly depress the accelerator pedal to WOT and then slowly return the pedal to closed throttle.
Repeat the procedure several times.
The APP Sensor 1 and 2 Agree/Disagree parameter should display Agree.
4. Observe the DTC information with a scan tool. DTCs P2122, P2123, P2127, P2128, or P2138 should not
set.
5. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You
may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure
Records data.

 

[maxpg]

CIRCUIT/SYSTEM TESTING
1. Ignition OFF, disconnect the harness connector at the B107 accelerator pedal assembly.
2. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power
down. Test for less than 5 ohms between the low reference circuit terminals listed below and ground.
 Low reference circuit terminal 4 or A
 Low reference circuit terminal 5 or D
 If greater than the specified range, test the appropriate low reference circuit for a short to voltage,
or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
3. Ignition ON, test for 4.8-5.2 V between both 5 V reference circuit terminals listed below and ground.
 5 V reference circuit terminal 1 or C
 5 V reference circuit terminal 2 or F
 If less than the specified range, test the appropriate 5 V reference circuit for a short to ground or
open/high resistance. If the circuit tests normal, replace the K20 ECM.
 If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit
tests normal, replace the K20 ECM.
4. Verify the appropriate APP sensor voltage parameter is at 0 V.
 If greater than the specified range, test the appropriate signal circuit terminal listed below for a
short to voltage. If the circuit tests normal, replace the K20 ECM.
 APP sensor 1 signal circuit terminal 3 or E
 APP sensor 2 signal circuit terminal 6 or B
5. Install a 3 A fused jumper wire between the appropriate signal circuit listed below and the 5 V reference
circuit terminal 1. Verify the appropriate APP sensor voltage parameter is greater than 4.8 V.
 APP sensor 1 signal circuit terminal 3 or E
 APP sensor 2 signal circuit terminal 6 or B
 If less than the specified range, test the appropriate signal circuit for a short to ground or an
open/high resistance. If the circuit tests normal, replace the K20 ECM.
6. If all circuits test normal, replace the B107 accelerator pedal assembly.

 

[AllTerrain1025]

The other thing that I forgot to mention, is that the code only gets thrown when going WOT. This was happening before I replaced both the pedal and throttle body, and it continues to happen afterwards. Would that point to a faulty ECM?

 

[SYDNESB]

The other thing that I forgot to mention, is that the code only gets thrown when going WOT. This was happening before I replaced both the pedal and throttle body, and it continues to happen afterwards. Would that point to a faulty ECM?

Did you perform a throttle relearn after replacing TB and AP? Did you use OEM parts?

 

[AllTerrain1025]

Did you perform a throttle relearn after replacing TB and AP? Did you use OEM parts?

I used OEM parts. I disconnected the battery while performing the work. The only relearn procedure I found online (without using a scanner) is to do the idle for 3 minutes, shut off for 5 minutes, then do another 3 minute idle. Is there something else that you can point me to?

I am considering upgrading my scanner so I can do throttle relearns right through it, but funds are a bit tight right now.

 

[AllTerrain1025]

Decide to take the valve cover off today as I also suspect the timing chain, and sure enough, I can see a broken upper guide. I guess I will be doing this as well and then chasing down the P2138.

 

[AllTerrain1025]

Here is another question that I have been led to after researching timing kits until my head spins. The Cloyes kit with the replacement phasers includes two of the same phasers. In doing a VIN decode, I find that my engine is the LEA engine, even though there are no flex fuel marking on it, nor does it have the yellow cap. I would think that the phasers would have to be different for the intake and exhaust sides, wouldn't they?

 

[AllTerrain1025]

I replaced the timing chain last weekend and everything was going fine, but now it is throwing a P0017 code which leads me to believe that I should replace the cam position sensors. The engine is running fine and other than the P0017, nothing else is wrong. The one thing that I am tackling tomorrow is an oil change and pulling the pan to see if there is any leftovers from when the old top timing guide disintegrated.

And, just for fun, the P2138 is still showing as a pending code as well.

The saga continues.