P2128 HIGH VOLTAGE AT THE THROTTLE VALIDATION SWITCH

When Monitored and Set Condition:

When Monitored: Key on.
Set Condition: Both Idle and Not Idle switches are in the same state simultaneously for a calibrated amount of time.

POSSIBLE CAUSES

• (K565) IDLE SWITCH CIRCUIT SHORTED TO (K922) RETURN CIRCUIT
• (K556) NOT IDLE SWITCH CIRCUIT SHORTED TO (K922) RETURN CIRCUIT
• (K565) IDLE SWITCH CIRCUIT SHORTED TO GROUND
• (K556) NOT IDLE SWITCH CIRCUIT SHORTED TO GROUND
• (K565) IDLE SWITCH SHORTED TO (K556) NOT IDLE SWITCH
• (K565) IDLE SWITCH SHORTED TO (K556) NOT IDLE SWITCH INSIDE ECM
• ECM
• INTERMITTENT CONDITION
• (K29) APPS NO.2 SIGNAL CIRCUIT SHORTED TO (K854) APPS NO.2 5-VOLT SUPPLY CIRCUIT
• (K29) APPS NO.2 SIGNAL CIRCUIT SHORTED TO OTHER CIRCUITS IN THE ECM HARNESS
• ECM
• APPS
• 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.
   Ignition on, engine not running. Measure the voltage between the (K565) idle switch circuit of the APPS harness connector and (K922) return circuit. Is the voltage between 4.5 and 5.5 volts?
   Yes --> Replace the APPS. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
   No --> Go To 3
3. Measure the voltage between the (K556) not idle switch circuit of the APPS harness connector and (K922) return circuit. Is the voltage between 4.5 and 5.5 volts?
   Yes --> Replace the APPS. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
   No --> Go To 4
4. Turn the ignition off. Disconnect the ECM harness connectors.
   NOTE: Check connectors - Clean/repair as necessary.
   Measure the resistance between the (K565) idle switch circuit of the APPS harness connector and battery negative. Is the resistance greater than 100 K Ohms?
   Yes --> Go To 5
   No --> Repair the (K565) Idle switch circuit shorted to ground. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
5. Measure the resistance between the (K556) not idle switch circuit of the APPS harness connector and battery negative. Is the resistance greater than 100 K Ohms?
   Yes --> Go To 6
   No --> Repair the (K556) not Idle switch circuit shorted to ground. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
6. Measure the resistance between the (K65) idle switch circuit of the APPS harness connector and the (K556) not idle switch circuit of the APPS harness connector. Is the resistance less than 10 Ohms?
   Yes --> Repair the (K565) idle switch circuit shorted to the not (K556) not idle switch circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
   No --> Go To 7
7. Reconnect the ECM harness connectors. Measure the resistance between the (K565) idle switch circuit of the APPS harness connector and the (K556) not idle switch circuit of the APPS harness connector. Is the resistance less than 10 Ohms?
   Yes --> Replace and program the ECM in accordance with the Service Information. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
   No --> Go To 8
8. Ignition on, engine not running. Measure the voltage between the (K565) idle switch circuit of the APPS harness connector and battery negative. Is the voltage between 4.5 and 5.5 volts?
   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 ECM harness connectors. Disconnect the APPS harness connector.
   NOTE: Check connectors - Clean/repair as necessary.
   Measure the resistance between the (K29) APPS No. 2 signal circuit in the sensor harness connector and the (K854) APPS No. 2 5-volt supply circuit in the sensor harness connector. Is the resistance greater than 100 K ohms?
   Yes --> Go To 10
   No --> Repair the (K29) APPS No. 2 signal circuit shorted to (K854) APPS No. 2 5-volt supply circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
10. Measure the resistance between the APPS No. 2 signal circuit at the ECM harness connector and all other circuit in the ECM harness connector. Is the resistance greater than 100 K ohms?
    Yes --> Go To 11
    No --> Repair the (K29) APPS No. 2 Signal circuit shorted to other circuits in the ECM harness connector. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
11. Reconnect the ECM harness connector. Reconnect the APPS harness connector. Ignition on, engine not running. While monitoring the DRBIII®, disconnect the APPS harness connector. Did DTC P2122 and P2127 set?
    Yes --> Go To 12
    No --> Replace and program the ECM in accordance with the Service Information. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
12. 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 --> Test Complete.
    No --> Replace the APPS. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).