P0121
P0121 - APPS 5-volt SUPPLY CIRCUIT
When Monitored and Set Condition
- When Monitored: Ignition on.
- Set Condition: When the PCM recognizes the APP Sensor 5-volt Supply circuit voltage is below 1.0 volt or higher than 5.2 volts.
Diagnostic Test
1. PRE-DIAGNOSTIC CHECK OUT
NOTE: Always perform diagnostics with a fully charged battery.
NOTE: Check connectors - Clean/repair as necessary. Poor pin to terminal connections can set DTCs.
NOTE: Check for applicable TSBs related to the problem.
Turn the ignition on.
With the DRB III(R), read PCM DTCs.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors. Repair as necessary.
Perform this procedure prior to symptom diagnosis.
Continue
- Go To 2
2. CHECK FOR CURRENT DTC
NOTE: If the PCM detects and stores a DTC, the PCM also stores the engine/vehicle operating conditions under which the DTC was set. Some of these conditions are displayed on the DRB III(R) at the same time the DTC is displayed.
NOTE: Before erasing stored DTCs, record these conditions. Attempting to duplicate these conditions may assist when checking for a DTC.
Turn the ignition on.
With the DRB III(R), clear PCM DTCs.
NOTE: It maybe necessary to road test the vehicle for this DTC to set.
With the DRB III(R), read PCM DTCs.
Did this DTC set again?
Yes
- Go To 3
No
- Go To 11
3. CHECK THE APP SENSOR 5-volt SUPPLY CIRCUIT VOLTAGE
Turn the ignition off.
Disconnect the APP Sensor harness connector.
NOTE: Check connectors - Clean/repair as necessary.
Turn the ignition on.
Measure the voltage of the APP Sensor 5-volt Supply circuit at the APP Sensor harness connector.
Is the voltage between 4.7 and 5.2 volts?
Yes
- Go To 4
No
- If the voltage is above 5.2 volts, Go To 5
- If the voltage is below 4.7 volts, Go To 7
4. CHECK THE APPS
With the ignition on.
With the DRB III(R), clear PCM DTCs.
NOTE: It maybe necessary to road test the vehicle for this DTC to set.
With the DRB III(R), read the PCM DTCs.
Did this DTC set again?
Yes
- Go To 9
No
- Replace the Accelerator Pedal Position Sensor.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2
5. CHECK THE APP SENSOR 5-volt SUPPLY CIRCUIT FOR A SHORT TO VOLTAGE
Turn the ignition off.
Disconnect the PCM C4 harness connector.
NOTE: Check connectors - Clean/repair as necessary.
Turn the ignition on.
Measure the voltage of the APP Sensor 5-volt Supply circuit at the APP Sensor harness connector.
Is the voltage below 1.0 volt?
Yes
- Go To 6
No
- Repair the APP Sensor 5-volt Supply circuit for a short to voltage.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2
6. CHECK THE TP SENSOR 5-volt SUPPLY CIRCUIT FOR A SHORT TO VOLTAGE
Turn the ignition off.
Disconnect the PCM C3 harness connector.
Disconnect the Throttle Body harness connector.
NOTE: Check connectors - Clean/repair as necessary.
Turn the ignition on.
Measure the voltage of the 5-volt Supply circuit at the Throttle Body harness connector.
Is the voltage below 1.0 volt?
Yes
- Replace and program the Powertrain Control Module.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2
No
- Repair the 5-volt Supply circuit for a short to voltage.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2
7. MEASURE THE RESISTANCE BETWEEN GROUND AND THE TP SENSOR 5-volt SUPPLY CIRCUIT
Turn the ignition off.
Disconnect the PCM C3 harness connector.
Disconnect the Throttle Body harness connector.
NOTE: Check connectors - Clean/repair as necessary.
Measure the resistance between ground and the 5-volt Supply circuit at the Throttle Body harness connector.
Is the resistance above 100 kohms?
Yes
- Go To 8
No
- Repair the 5-volt Supply circuit for a short to ground.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2
8. MEASURE RESISTANCE BETWEEN THE TP SENSOR 5-volt SUPPLY CIRCUIT AND SENSOR GROUND CIRCUITS
With the ignition off.
Measure the resistance between the 5-volt Supply circuit and all Sensor Ground circuits in the PCM C3 harness connector.
Is the resistance above 100 kohms for all measurements?
Yes
- Go To 9
No
- Repair the 5-volt Supply circuit for a short to the Sensor Ground circuit that measured below 100 kohms.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2
9. MEASURE THE RESISTANCE BETWEEN GROUND AND THE APP SENSOR 5-volt SUPPLY CIRCUIT
With the ignition off.
Disconnect the PCM C4 harness connector.
NOTE: Check connectors - Clean/repair as necessary.
Measure the resistance between ground and the APP Sensor 5-volt Supply circuit at the PCM C4 harness connector.
Is the resistance above 100 kohms?
Yes
- Go To 10
No
- Repair the APP Sensor 5-volt Supply circuit for a short to ground.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2
10. MEASURE RESISTANCE BETWEEN THE APP SENSOR 5-volt SUPPLY CIRCUIT AND SENSOR GROUND CIRCUITS
With the ignition off.
Measure the resistance between the APP Sensor 5-volt Supply circuit and all Sensor Ground circuits in the PCM C4 harness connector.
Is the resistance above 100 kohms for all measurements?
Yes
- Replace and program the Powertrain Control Module.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2
No
- Repair the APP Sensor 5-volt Supply circuit for a short to the Sensor Ground circuit that measured below 100 kohms.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2
11. INTERMITTENT WIRING AND CONNECTORS
The condition that caused this DTC to set is currently not present. Inspect the related wiring harness for a possible intermittent condition.
NOTE: Check connectors - Clean/repair as necessary. Poor pin to terminal connections can set DTCs.
NOTE: Check for any Technical Service Bulletins that may apply.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors specific to this DTC. Wiggle the wires while checking for shorts and open circuits.
Were there any problems found?
Yes
- Repair as necessary.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2
No
- The condition that caused this DTC to set is currently not present. Inspect the related wiring harness for a possible intermittent condition.