P0120

DTC P0120 or P0220

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Diagnostic System Check - Vehicle
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0120
- Throttle Position (TP) Sensor 1 Circuit

DTC P0220
- Throttle Position (TP) Sensor 2 Circuit

Diagnostic Fault Information






Typical Scan Tool Data






Circuit/System Description

The throttle actuator control (TAC) system uses 2 throttle position (TP) sensors to monitor the throttle position. The TP sensors 1 and 2 are located within the throttle body assembly. Each sensor has the following circuits:

* A 5-volt reference circuit
* A low reference circuit
* A signal circuit

Two processors are also used to monitor the TAC system data. Both processors are located within the powertrain control module (PCM). Each signal circuit provides both processors with a signal voltage proportional to throttle plate movement. Both processors monitor each other's data to verify that the indicated TP calculation is correct.

Conditions for Running the DTC

* The system voltage is more than 5.23 volts.
* The ignition is in Unlock/Accessory or Run position.

Conditions for Setting the DTC

The indicated TP calculation between the processors does not agree.

Action Taken When the DTC Sets

* The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
* The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
* The control module commands the TAC system to operate in the Reduced Engine Power mode.
* A message center or an indicator displays Reduced Engine Power.
* Under certain conditions the control module commands the engine OFF.

Conditions for Clearing the MIL/DTC

* The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
* A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
* A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
* Clear the MIL and the DTC with a scan tool.

Circuit/System Verification

* Ignition ON, use a scan tool to observe the TP sensor 1 voltage with the accelerator pedal in the rest position. Voltage should be between 0.27-4.67 volts.
* With the ignition ON, observe the TP sensor 2 voltage with the accelerator pedal in the rest position with a scan tool. Voltage should be between 0.31-4.7 volts.

Circuit/System Testing

1. Clear DTCs with the scan tool. Operate the vehicle within the Conditions for Running the DTC or within the conditions that you observed from the Freeze Frame/Failure Records.
2. Ignition ON, use a scan tool to observe the TP sensor 1 voltage with the accelerator pedal in the rest position. Voltage should be between 0.27-4.67 volts.

• If more than 4.67 volts, test the low reference for an open. If the circuit tests normal, replace the control module.
• If less than 0.27 volt, test the TP sensor 1 signal circuit for a short to ground. If the circuit tests normal, replace the control module.

3. With the ignition ON, observe the TP sensor 2 voltage with the accelerator pedal in the rest position with a scan tool. Voltage should be between 0.31-4.7 volts.

• If more than 4.7 volts, test the low reference for an open. If the circuit tests normal, replace the control module.
• If less than 0.31 volt, test the TP sensor 2 signal circuit for a short to ground. If the circuit tests normal, replace the control module.

4. Ignition ON, use a scan tool to observe the DTCs.

• If DTC P0120 is the only code set, replace the PCM.
• If DTC P0220 is the only code set, replace the PCM.
• If any other codes are set, refer to that code first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle. Diagnostic Trouble Code Descriptions

5. Disconnect the throttle body harness connector and verify the scan tool TP sensor 1 voltage is less than 0.1 volt.

• If more than 0 volt, test the TP sensor 1 signal circuit for a short to voltage. If the circuit tests normal, replace the control module.

6. With the throttle body harness connector still disconnected, verify the scan tool TP sensor 2 voltage is more than 4.8 volts.

• If less than 4.8 volts, test the TP sensor 2 signal circuit for a short to ground. If the circuit tests normal, replace the control module.

7. Ignition ON, test for 4.8-5.2 volts between both 5-volt reference circuits and the negative terminal of the battery.

• If more than 5.2 volts, test both 5-volt reference circuits for a short to voltage. If the circuit tests normal, replace the control module.
• If less than 4.8 volts, test both the 5-volt reference circuits for an open or short to ground. If the circuit tests normal, replace the control module.

8. Install a 3A fused jumper wire between the signal circuit and the 5-volt reference circuit of the TP sensor 1 and verify the TP sensor 1 voltage is more than 4.8 volts.

• If less than 4.8 volts, test the TP sensor 1 signal circuit for an open. If the circuit tests normal, replace the control module.

9. Install a test lamp between the signal circuit and the negative terminal of the battery of the TP sensor 2 and verify the TP sensor 2 voltage is less than 0.1 volt.

• If more than 0.1 volt, test the TP sensor 2 signal circuit for an open. If the circuit tests normal, replace the control module.
• If test lamp illuminates, test the TP sensor 2 signal circuit for a short to voltage. If the circuit tests normal, replace the control module.

10. If all circuits test normal, replace the throttle body.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

Refer to Programming and Relearning for PCM setup and programming. Programming and Relearning