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Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. 3:  This step tests the internal circuits of the APP sensor 1 throughout its range of motion. If this DTC sets when slowly moving the pedal from the rest position to wide open throttle (WOT), replace the APP assembly for an internal fault.
  2. 7:  This step tests for high resistance in the low reference circuit of the APP sensor 1. The ECM must be completely powered down to obtain an accurate resistance reading. It may take up to 30 minutes for the ECM to power down after the ignition key is removed. Removal of the ECM/TCM fuse allows the ECM to power down completely.
DTC P2123

Step Action Values Yes No
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Control Module (ECM) Connector End Views or Engine Controls Connector End Views
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
2
  1. Turn ON the ignition, with the engine OFF.
  2. Observe the accelerator pedal position (APP) sensor 1 voltage parameter, with a scan tool.
Is the voltage more than the specified value?		 4.7 V Go to Step 5  Go to Step 3 
3 
  1. Observe the DTC information with a scan tool.
  2. Slowly depress the accelerator pedal to wide open throttle (WOT), then slowly return the accelerator pedal to the closed position.
  3. Repeat this action several times.
Did the DTC fail this ignition?		 - Go to Step 13  Go to Step 4 
4
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?		 - Go to Step 5  Go to Diagnostic Aids
5
  1. Turn OFF the ignition.
  2. Disconnect the APP sensor harness connector. Refer to Accelerator Pedal with Position Sensor Replacement .
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the APP sensor 1 voltage with the scan tool.
Is the voltage less than the specified value?		 0.1 V Go to Step 6  Go to Step 10 
6 Measure the voltage from the 5-volt reference circuit of the APP sensor 1 to a good ground, with a DMM.
Is the voltage more than the specified value?		 6 V Go to Step 9  Go to Step 7 
7 
  1. Turn OFF the ignition.
  2. Remove the engine control module (ECM)/transmission control module (TCM) fuse from the underhood fuse block.
    3. NOTE: Do NOT use a test lamp to test the continuity of the circuit. Damage to the control module may occur due to excessive current draw.
  3. Measure the resistance from the low reference circuit of APP sensor 1 to a good ground, with a DMM.
Is the resistance less than the specified value?		 10 Ω Go to Step 11  Go to Step 8 
8
  1. Turn OFF the ignition.
  2. Disconnect the ECM.
    3. IMPORTANT: A short to voltage on the low reference circuit may cause internal ECM damage and sensor damage.
  3. Test the low reference circuit of the APP sensor 1 for an open, for a short to voltage, or for a high resistance. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 15  Go to Step 12 
9
IMPORTANT: The 5-volt reference circuits are internally and externally connected at the controller. Other sensors that share the 5-volt reference circuit may also have DTCs set. Disconnecting a sensor on the shared 5-volt reference circuit may isolate a shorted sensor. Review the electrical schematic and diagnose the shared circuits and sensors.
Test the 5-volt reference circuit of the APP sensor 1 for a short to voltage. Refer to Circuit Testing and Wiring Repairs .Did you find and correct the condition?		 - Go to Step 15  Go to Step 12 
10 Test the signal circuit of the APP sensor 1 for a short to voltage. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 15  Go to Step 12 
11 Test for shorted terminals and poor connections at the APP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		 - Go to Step 15  Go to Step 13 
12 Test for shorted terminals and poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		 - Go to Step 15  Go to Step 14 
13 Replace the accelerator pedal assembly. Refer to Accelerator Pedal with Position Sensor Replacement .
Did you complete the replacement?		 - Go to Step 15  -
14 Replace the ECM. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?		 - Go to Step 15  -
15
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?		 - Go to Step 2  Go to Step 16 
16 Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List - Vehicle System OK
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