P2123 HIGH VOLTAGE AT THE APP SENSOR

When Monitored and Set Condition:

When Monitored: While the key is on and during engine operation.
Set Condition: The APPS signal circuit voltage at the ECM goes above 4.24 volts for more than 2 seconds.

POSSIBLE CAUSES

• APPS
• (K922) RETURN CIRCUIT OPEN
• (K22) SIGNAL CIRCUIT SHORTED TO (K851) 5-VOLT SUPPLY
• (K22) SIGNAL CIRCUIT SHORTED TO VOLTAGE
• ECM
• INTERMITTENT CONDITION
• (K167) APPS NO. 1 RETURN CIRCUIT OPEN
• (K23) APPS NO. 1 SIGNAL CIRCUIT SHORTED TO (K852) APPS NO. 1 5-VOLT SUPPLY
• (K23) APPS SIGNAL CIRCUIT SHORTED TO ANOTHER CIRCUIT
• INTERMITTENT CONDITION

DIAGNOSTIC PROCEDURE

NOTE: Refer to VERIFICATION TESTS for appropriate verification test procedures.

1. The diesel engine uses two types of throttle position sensors, depending on transmission configuration. Is the throttle position sensor is located on the engine?
   Yes --> Go To 2
   No --> Go To 9
2. Turn the ignition off. Disconnect the APPS harness connector.
   NOTE: Check connectors - Clean/repair as necessary.
   Measure the resistance between the (K22) signal circuit of the sensor to the (K851) 5-volt supply circuit of the sensor. Is the resistance between 1500 - 3000 Ohms with the accelerator pedal released?
   Yes --> Go To 3
   No --> Replace the APPS. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
3. Measure the resistance between the (K22) signal circuit of the sensor to the (K851) 5-volt supply circuit of the sensor.
   NOTE: Released resistance must be at least 1000 Ohms greater than depressed resistance.
   Is the resistance between 200 - 1500 Ohms with the accelerator pedal depressed?
   Yes --> Go To 4
   No --> Replace the APPS. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
4. Reconnect the APPS harness connector. Ignition on, engine not running. Using the DRBIII®, monitor the DTC while disconnecting the APPS harness connector Did P2122 set?
   Yes --> Replace the APPS. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
   No --> Go To 5
5. Turn the ignition off. Disconnect the ECM harness connectors. Disconnect the APPS harness connector.
   NOTE: Check connectors - Clean/repair as necessary.
   Measure the resistance of the APPS (K922) return circuit between the sensor harness connector and the ECM harness connector. Is the resistance less than 10 Ohms?
   Yes --> Go To 6
   No --> Repair the open (K922) return circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
6. Measure the resistance between the (K22) signal circuit in the sensor harness connector and the (K851) 5- volt supply circuit in the sensor harness connector. Is the resistance less than 10 Ohms?
   Yes --> Repair the (K22) signal circuit shorted to (K851) 5-volt supply circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
   No --> Go To 7
7. Measure the voltage between the (K22) signal circuit in the sensor harness connector and battery negative. Is the voltage greater than 1 volt?
   Yes --> Repair the (K22) signal circuit shorted to voltage. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
   No --> Go To 8
8. Reconnect the ECM harness connectors. Reconnect the disconnected APPS harness connector. Monitor the DRBIII® while disconnecting the APPS harness connector. Did P2122 set?
   Yes --> Refer to the SYMPTOM: INTERMITTENT CONDITION Symptom (Diagnostic Procedure). Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
   No --> Replace and program the ECM in accordance with the Service Information. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
9. Turn the ignition off. Disconnect the APPS harness connector. Disconnect the ECM harness connectors. Measure the resistance on the (K167) APPS No. 1 return circuit between the sensor harness connector and the ECM harness connector. Is the resistance less than 10 ohms?
   Yes --> Go To 10
   No --> Repair the (K167) APPS No. 1 return circuit open. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
10. Measure the resistance between the (K23) APPS No. 1 signal circuit in the sensor harness connector and the (K852) APPS No. 1 5-volt supply circuit in the sensor harness connector. Is the resistance greater than 100 K ohms?
    Yes --> Go To 11
    No --> Repair the (K23) APPS No. 1 signal circuit shorted to the (K852) 5-volt supply circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
11. Measure the resistance between the APPS No. 1 signal circuit at the ECM harness connector and all other circuits in the ECM harness connector. Is the resistance greater than 100 k ohms?
    Yes --> Go To 12
    No --> Repair the (K23) APPS No. 1 signal circuit shorted to another circuit in the engine harness. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
12. Reconnect the ECM harness connectors. Reconnect the APPS harness connector. While monitoring with the DRBIII®, disconnect the sensor connector. Did a APPS No. 1 and APPS No. 2 voltage too low DTC set?
    Yes --> Go To 13
    No --> Replace and program the ECM in accordance with the Service Information. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
13. Reconnect the APPS harness connector. Monitor the APPS No. 1 and APPS No. 2 voltage with the DRBIII® while depressing the throttle pedal. Is the voltage transition shown on the DRBIII® smooth while depressing the throttle?
    Yes --> Refer to the SYMPTOM: INTERMITTENT CONDITION Symptom (Diagnostic Procedure). Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    No --> Replace the APPS. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).