For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptors

DTC P0120: Throttle Position (TP) Sensor 1 Circuit
DTC P0122: Throttle Position (TP) Sensor 1 Circuit Low Voltage
DTC P0123: Throttle Position (TP) Sensor 1 Circuit High Voltage
DTC P0220: Throttle Position (TP) Sensor 2 Circuit
DTC P0222: Throttle Position (TP) Sensor 2 Circuit Low Voltage
DTC P0223: Throttle Position (TP) Sensor 2 Circuit High Voltage
DTC P2135: Throttle Position (TP) Sensor 1-2 Correlation

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
TP Sensor 1 Signal | P0122 | P2135 | P0122, P2135 | P0123 | P0068, P0120, P0121
TP Sensor 2 Signal | P0222 | P2135 | P0223, P2125 | P0223 | P0068, P0121, P0220
Throttle Position Sensor 1 and 25 V Reference | P0651 | P2135 | P0122, P0222 | P0651 | --
Throttle Position Sensor 1 and 2 Low Reference | -- | P2135 | P0123, P0223 | -- | --

### Typical Scan Tool Data

#### TP Sensor 1

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: With the engine running, turn the ignition ON Parameter Normal Range: 4.20-0.5 V
Throttle Position Sensor 1 and 25 V Reference | 0.04 V | 0.00 V | 4.98 V
TP Sensor 1 Signal | 0.00 V | 0.00 V | 4.98 V
Throttle Position Sensor 1 and 2 Low Reference | -- | 4.98 V | --

#### TP Sensor 2

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: With the engine running, turn the ignition ON Parameter Normal Range: 0.7-4.5 V
Throttle Position Sensor 1 and 25 V Reference | 0.04 V | 0 V | 3.63 V
TP Sensor 2 Signal | 0.00 V | 4.98 V | 4.98 V
Throttle Position Sensor 1 and 2 Low Reference | -- | 4.98 V | --

### Circuit 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 a signal circuit and share a 5-volt reference and low reference circuit.

Two processors are also used to monitor the TAC system data. Both processors are located in the engine control module (ECM). 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

• | DTCs P0601, P0602, P0603, P0604, P0606, P060D, P062F, P0641, P0651 are not set.

• | System voltage is greater than 5.23 volts.

• | The ignition switch is in Unlock/Accessory, Run or Crank.

• | DTCs P0120, P0122, P0123, P0222, P0223, and P2135 run continuously when the above conditions are met.

### Conditions for Setting the DTC

#### P0120

• | The TP sensor 1 voltage is less than 0.33 volt or more than 4.75 volts.

• | It occurs 79 times or 52 times continuously during the 159 tests.

#### P0122

• | The engine control module (ECM) detects the TP sensor voltage is less than 0.33 volt.

• | It occurs 79 times or 52 times continuously during the 159 tests.

#### P0123

• | The ECM detects the TP sensor 1 voltage is more than 4.58 volts.

• | It occurs 79 times or 55 times continuously during the 159 tests.

#### P0220

• | The TP sensor 2 voltage is less than 0.25 volt or more than 4.59 volts.

• | It occurs 79 times or 52 times continuously during the 159 tests.

#### P0222

• | The ECM detects the TP sensor 2 voltage is less than 0.25 volt.

• | It occurs 79 times or 52 times continuously during the 159 tests.

#### P0223

• | The ECM detects the TP sensor 2 voltage is more than 4.59 volts.

• | It occurs 79 times or 52 times continuously during the 159 tests.

#### P2135

• | The voltage differences between the TP sensor 1 and TP sensor 2 exceeds the predetermined value.

• | It occurs 79 times or 63 times continuously during the 159 tests.

### Action Taken When the DTC Sets

• | DTCs P0120, P0122, P0123, P0220, P0222, P0223, and P2135 are Type A DTCs.

• | The control module commands the TAC system to operate in the Reduced Engine Power mode.

• | The message center or the indicator displays Reduced Engine Power.

• | Under certain conditions the control module commands the engine OFF.

### Conditions for Clearing the DTC

DTCs P0120, P0122, P0123, P0220, P0222, P0223, and P2135 are Type A DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

• | Engine Controls Connector End Views

• | Engine Control Module Connector End Views

#### Description and Operation

Throttle Actuator Control (TAC) System Description

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Engine Control Module Scan Tool Information

### Circuit/System Verification

1. Ignition ON, observe the scan tool TP sensor 1, the reading should be between 4.5-0.40 volts and vary with accelerator pedal input.
2. Ignition ON, observe the scan tool TP sensor 2 voltage parameter. The reading should be between 0.35-4.59 volts and vary with accelerator pedal input.
3. Ignition ON, observe the scan tool TP sensors 1 and 2 parameters. The scan tool should indicate Agree.
4. Clear the 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.
5. Ignition ON, perform several accelerator pedal sweeps, then observe the previous TP sensor parameters and DTC information with the scan tool.

⇒ | If only DTC P0120 or P0220 are set, and all of the previous TP sensor parameters are normal, replace the ECM.

⇒ | If DTC P0641 or P0651 is set, refer to DTC P0641 or P0651 .

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the throttle body. Allow sufficient time for the ECM to completely power down.
2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal C and ground.

⇒ | If more than 5 ohms, test the low reference circuit for an open/high resistance. If the circuit test normal, replace the ECM.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal E and ground.

⇒ | If less than 4.8 volts, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit test normal, replace the ECM.

⇒ | If greater than 5.2 volts, test the 5-volt reference circuit for short to voltage. If the circuit test normal, replace the ECM.

4. Verify that the scan tool TP sensor 1 voltage is less than 0.1 volt.

⇒ | If greater than 0.1 volt, test the signal circuit terminal D for a short to voltage. If the circuit test normal, replace the ECM.

5. Verify that the scan tool TP sensor 2 voltage is greater than 4.8 volts.

⇒ | If less than 4.8 volts, test the signal circuit for a short to ground. If the circuit test normal, replace the ECM.

6. Install a 3-amp fused jumper wire between the TP sensor signal circuit terminal D and the 5-volt reference circuit terminal E, then verify that the TP sensor 1 voltage is greater than 4.8 volts.

⇒ | If less than 4.8 volts, test the TP sensor 1 signal circuit for short to ground or an open/high resistance. If the circuit test normal, replace the ECM.

7. Install a 3-amp fused jumper wire between the TP sensor 2 signal circuit terminal F and the low reference circuit terminal C, then verify that the TP sensor 2 voltage is less than 0.1 volt.

⇒ | If greater than 0.1 volt, test the TP sensor 2 signal circuit for a short to voltage or an open/high resistance. If the circuit test normal, replace the ECM.

8. Ignition OFF, disconnect the harness connector at the ECM.
9. Test for less than 5 ohms on all TP sensor circuits between the following terminals:

• | ECM C2 signal circuit terminal 64 to TP terminal D

• | ECM C2 signal circuit terminal 68 to TP terminal F

• | ECM C2 5-volt reference circuit terminal 44 to TP terminal E

⇒ | If greater than 5 ohms, repair the affected circuit.

10. Test for infinite resistance between TP sensor signal circuit terminal D and TP sensor 2 signal circuit terminal E.

⇒ | If less than infinite resistance, repair the short between TP sensor 1 signal circuit and TP sensor 2 signal circuits.

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Throttle Body Assembly Replacement

• | Control Module References for ECM replacement, setup, and programming