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P2121






P2121-ACCELERATOR PEDAL POSITION SENSOR 1 PERFORMANCE





For complete wiring diagrams refer to Diagrams/Electrical.


Theory of Operation

The throttle pedal produces two voltage signals proportional to the pedal movement. The voltages are created by electronic circuitry within the pedal assembly. The primary signal varies between 0 and 5 volts and the secondary signal varies between 0 and 2.5 volts. The Engine Control Module uses the two signals to validate throttle pedal position to control engine fueling. The ECM illuminates the MIL lamp immediately after the diagnostic runs and fails. During this time the customer will be in a limp home mode. The ECM will turn off the MIL lamp after the diagnostic runs and passes in 4 consecutive drive cycles.

- When Monitored:

While the engine is running

- Set Condition:

The ECM detected a conformance error between APPS 1 and APPS 2







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test


1. OTHER DTCS PRESENT

Using the scan tool, check for any additional APPS fault codes

Do you have any additional APPS faults?

Yes

- troubleshoot other DTCs first, Go To2

No

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition

2. APPS HARNESS

Verify that the APPS is connected.

Inspect the harness and the APPS connector.

Are any pins damaged?

Yes

- Repair or replace the harness.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To3

3. APPS

Monitor the APPS 1 and APPS 2 voltage with the scan tool while depressing the accelerator pedal.

Is the voltage transition shown on the scan tool smooth while depressing the accelerator pedal and is the voltage from APPS 1 twice as much as the voltage from APPS 2?

Yes

- Go To4

No

- Replace the APPS.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

4. (K23) APPS 1 SIGNAL CIRCUIT OPEN

Disconnect the C2 ECM harness connector.

Disconnect the APPS connector.


NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance of the (K23) APPS 1 Signal circuit between the APPS connector and the C2 ECM connector.

Is the resistance below 10 ohms?

Yes

- Go To5

No

- Repair the open in the (K23) APPS 1 Signal circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

5. (K852) 5-VOLT SUPPLY CIRCUIT OPEN

Measure the resistance of the (K852) 5-volt Supply circuit between the APPS connector and the ECM connector.

Is the resistance below 10 ohms?

Yes

- Go To6

No

- Repair the open in the 5-volt Supply circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

6. (K23) APPS 1 SIGNAL CIRCUIT SHORTED TO GROUND





Measure the resistance between ground and the APPS 1 Signal circuit at the sensor connector.

Is the resistance greater than 100 K ohms?

Yes

- Go To 7

No

- Repair the short to ground in the (K23) APPS 1 Signal circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

7. (K23) APPS 1 SIGNAL CIRCUIT SHORTED TO OTHER CIRCUITS

Measure the resistance between the (K23) APPS 1 Signal circuit and all other circuits in the ECM connector.

Is the resistance greater than 100 K ohms for any of the other circuits?

Yes

- Go To 8

No

- Repair the shorted (K23) APPS Signal circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

8. (K852) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND





Measure the resistance between the ground and the (K852) 5-volt Supply circuit at the sensor connector.

Is the resistance greater than 100 K ohms?

Yes

- Go To 9

No

- Repair the short to ground in the (K852) 5-volt Supply circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

9. (K852) 5-VOLT SUPPLY CIRCUIT SHORTED TO OTHER CIRCUITS

Measure the resistance between the (K852) 5-volt Supply circuit and all other circuits in ECM harness connector.

Is the resistance greater than 100 K ohms for each circuit?

Yes

- Go To 10

No

- Repair the short in the (K852) 5-volt Supply circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

10. (K167) APPS 1 RETURN CIRCUIT OPEN

Measure the resistance of the (K167) APPS 1 Return circuit between the sensor connector and the ECM connector.

Is the resistance less than 10 ohms?

Yes

- Go To 11

No

- Repair the open in the (K167) APPS Return circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

11. (K23) APPS 1 SIGNAL CIRCUIT SHORTED TO (K852) 5-volt SUPPLY CIRCUIT





Measure the resistance between the (K23) APPS 1 Signal circuit and the (K852) 5-volt Supply circuit at the sensor harness connector

Is the resistance greater than 100 K ohms?

Yes

- Go To 12

No

- Repair the short between the (K23) APPS Signal circuit and the (K852) 5-volt Supply circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

12. (K167) APPS 1 RETURN CIRCUIT SHORTED TO OTHER CIRCUITS

Measure the resistance between the (K167) APPS 1 Return circuit at and all other circuits in the ECM connector.

Is the resistance below 10 ohms?

Yes

- Go To 13

No

- Repair the short in the (K167) APPS Return circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

13. (K29) APPS 2 SIGNAL CIRCUIT OPEN

Measure the resistance of the (K29) APPS 2 Signal circuit between the APPS connector and the ECM connector.

Yes

- Go To14
-

No

- Repair the open in the (K29) APPS 2 Signal circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

14. (F854) 5-VOLT SUPPLY CIRCUIT OPEN

Measure the resistance of the (F854) 5-volt Supply circuit between the APPS connector and the ECM connector.

Is the resistance less than 10 ohms?

Yes

- Go To15
-

No

- Repair the open in the (F854) 5-volt Supply circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

15. (K29) APPS 2 SIGNAL CIRCUIT SHORTED TO GROUND





Measure the resistance between ground and the (K29) APPS 2 Signal circuit at the sensor connector.

Is the resistance greater than 100 K ohms?

Yes

- Go To 16

No

- Repair the short to ground in the (K29) APPS 2 Signal circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

16. (K29) APPS 2 SIGNAL CIRCUIT SHORTED TO OTHER CIRCUITS

Measure the resistance between the (K29) APPS 2 Signal circuit and all other circuits in the ECM harness connector.

Is the resistance greater than 100 K ohms?

Yes

- Go To 17

No

- Repair the shorted (K29) APPS 2 Signal circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

17. (F854) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND





Measure the resistance between ground and the (F854) 5-volt Supply circuit at the sensor connector.

Is the resistance greater than 100 K ohms?

Yes

- Go To 18

No

- Repair the short to ground in the (F854) 5-volt Supply circuit.
- Perform POWERTRAIN VERIFICATION TEST).

18. (F854) 5-VOLT SUPPLY CIRCUIT SHORTED TO OTHER CIRCUITS

Measure the resistance between the (F854) 5-volt Supply circuit and all other circuits in the C2 ECM harness connector.

Is the resistance greater than 100 K ohms?

Yes

- Go To 19

No

- Repair the shorted (F854) 5-volt Supply circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

19. (K400) APPS 2 RETURN CIRCUIT OPEN

Measure the resistance of the (K400) APPS 2 Return circuit between the APPS connector and the C2 ECM connector.

Is the resistance less than 10 ohms?

Yes

- Go To 20

No

- Repair the open in the (K400) APPS 2 Return circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

20. (K29) APPS 2 SIGNAL CIRCUIT SHORTED TO (F854) 5-VOLT SUPPLY CIRCUIT





Measure the resistance between the (K29) APPS 2 Signal circuit and the (F854) 5-volt Supply circuit in the APPS harness connector.

Is the resistance greater than 100 K ohms?

Yes

- Go To 21

No

- Repair the short between the (K29) APPS 2 Signal circuit and the (F854) 5-volt Supply circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

21. (K400) APPS 2 RETURN CIRCUIT SHORTED TO OTHER CIRCUITS

Measure the resistance between the (K400) APPS 2 Return circuit and all other circuits in the ECM connector.

Is the resistance greater than 100 K ohms?

Yes

- Go To 22

No

- Repair the shorted (K400) APPS 2 Return circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

22. ECM

Reconnect the ECM connectors.

Reconnect the APPS connector.

Turn Ignition on, engine off.

While monitoring with the scan tool, disconnect the sensor connector.

Did a APPS 1 and APPS 2 voltage too low DTC set?

Yes

- Go To 23

No

- Replace the ECM.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

23. APPS

Reconnect the APPS connector.

Monitor the APPS 1 and APPS 2 voltage with the scan tool while depressing the accelerator pedal.

Is the voltage transition shown on the scan tool smooth while depressing the accelerator and is the voltage from APPS 1 twice as much as the voltage from APPS 2?

Yes

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition

No

- Replace the APPS.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
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