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John
John, GMC Technician
Category: GM
Satisfied Customers: 9176
Experience:  ASE MASTER TECHNICIAN/40 years experience
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2004 envoy: gmc..reduced power..check engine light..i need an ecm

Customer Question

i have a p2138 code on gmc 2004 envoy i tried erasing the code but the code cannot be erased and i have a reduced power light in connection with that check engine light, do i need an ecm? how to erase the code and how to correct the problem?
Submitted: 6 years ago.
Category: GM
Expert:  John replied 6 years ago.

Hello & Welcome,

 

 

The accelerator pedal position (APP) sensors 1 and 2 are located within the accelerator pedal assembly. Each sensor has the following circuits:

A 5-volt reference circuit
A low reference circuit
A signal circuit

This provides the powertrain control module (PCM) with a signal voltage proportional to accelerator pedal movement. The APP sensor 1 signal voltage at rest position is near the low reference and increases as the pedal is actuated. The APP sensor 2 signal voltage at rest position is near the 5-volt reference and decreases as the pedal is actuated.

This problem is usually caused by a open or shorted in the accelerator pedal position sensor harness or the APP sensor itself.I suggest testing the wiring from t the sensor to the throttle body before replacing the APP sensor.

 

Accelerator Pedal Position Sensor Replacement


    Object Number: 899725  Size: SH

    Notice: Handle the electronic throttle control components carefully. Use cleanliness in order to prevent damage. Do not drop the electronic throttle control components. Do not roughly handle the electronic throttle control components. Do not immerse the electronic throttle control components in cleaning solvents of any type.

    Important: If the vehicle is equipped with adjustable pedals,Disconnect the accelerator pedal position (APP) sensor electrical connector.
    Object Number: 742494  Size: SH

  1. Remove the 3 APP sensor bolts (1).
  2. Remove the APP sensor (2).

    .


    Object Number: 899728  Size: SH

  1. Install the APP sensor.
  2. Install the 3 APP sensor bolts (1).

    Tighten
    Tighten the bolts to 20 N·m (15 lb ft).


    Object Number: 899725  Size: SH

  3. Connect the APP sensor electrical connector.
  4. Verify that the vehicle meets the following conditions:
    The vehicle is not in a reduced engine power mode.
    The ignition is ON.
    The engine is OFF.
  5. Connect a scan tool in order to test for a proper throttle-opening and throttle-closing range.
  6. Operate the accelerator pedal and monitor the throttle angles. The accelerator pedal should operate freely, without binding, between a closed throttle, and a wide open throttle.
Customer: replied 6 years ago.
i already done the wire to wire resistance check from ecm plug to the sensor plug and the test shows that the wires are all ok 0 resistance on both end for each color and no short circuit for each color it reads infinity in ohmeter for different color. the pedal sensor consist of two potmeter, as i monitored the reference voltage for both potmeter are both equal to 4.9volts and the signal one is near to the 4.9v and decreases as i depress the pedal and the other potmeter signal is almost near to the ground and increases to 4.9v as i depress the pedal. the unusual thing that i observed is that even i erased the code without turning the key off the code is still there. was this normal? code can not be reset.
Customer: replied 6 years ago.
Relist: answer is known by our tech and already done but not cure the problem need more information.
answer is known by our tech and already done but not cure the problem need more information
Expert:  John replied 6 years ago.
I guess you do not want my help,so I hope you have a good day.LOL........................