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 P0121: Throttle Position (TP) Sensor 1 Performance
DTC P0122: Throttle Position (TP) Sensor 1 Circuit Low Voltage
DTC P0123: Throttle Position (TP) Sensor 1 Circuit High Voltage
DTC P0221: Throttle Position (TP) Sensor 2 Performance
DTC P0222: Throttle Position (TP) Sensor 2 Circuit Low Voltage
DTC P0223: Throttle Position (TP) Sensor 2 Circuit High Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
5-Volt Reference | -- | -- | P0122, P0222 | -- | --
Throttle Position Sensor 1 Signal | P0122 | P0121 | P0123 | P0123 | P0121
Throttle Position Sensor 2 Signal | P0222 | P0221 | P0222 | P0223 | P0221
Low Reference | -- | -- | P0123, P0223 | -- | --

### Typical Scan Tool Data

#### TP Sensor 1

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: The engine is operating at idle. Parameter Normal Range: TP Sensor 1 11-14%, 0.65-0.85 Volts
5-Volt Reference | 0%, 0 Volts | 0%, 0 Volts | 100%, 5 Volts
TP Sensor 1 Signal | 0%, 0 Volts | 0%, 0 Volts | 100%, 5 Volts
Low Reference | -- | 100%, 5 Volts | --

#### TP Sensor 2

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: The engine is operating at idle. Parameter Normal Range: TP Sensor 2 4.1-4.3 Volts
5-Volt Reference | 0 Volts | 0 Volts | 5 Volts
TP Sensor 2 Signal | 0 Volts | 5 Volts | 5 Volts
Low Reference | -- | 5 Volts | --

### Circuit/System Description

The throttle body assembly contains 2 throttle position (TP) sensors. The TP sensors are mounted to the throttle body assembly and are not serviceable. The TP sensors provide a signal voltage that changes relative to throttle blade angle. The engine control module (ECM) supplies the TP sensors with a common 5-volt reference circuit, a common low reference circuit, and 2 independent signal circuits.

The TP sensors have opposite functionality. TP sensor 1 signal voltage increases from below 1 volt at idle to above 4 volts at wide open throttle (WOT). TP sensor 2 signal voltage decreases from above 4 volts at idle to below 1 volt at WOT.

### Conditions for Running the DTC

#### P0121 or P0221

• | DTCs P0101, P0102, P0103, P0107, or P0108 are not set.

• | The ignition is ON or the engine is running.

• | The actual TP value is less than 90 percent.

• | The DTCs run continuously once the above conditions are met.

#### P0122, P0123, P0222, or P0223

• | The ignition is ON or the engine is running.

• | The DTCs run continuously once the above condition is met.

### Conditions for Setting the DTC

#### P0121 or P0221

The ECM detects the difference between TP sensor 1 and TP sensor 2 is greater than 6 percent for greater than 30 seconds.

#### P0122

The ECM detects that the TP sensor 1 voltage is less than 0.4 volt for less than 1 second.

#### P0123

The ECM detects that the TP sensor 1 voltage is greater than 4.6 volts for less than 1 second.

#### P0222

The ECM detects that the TP sensor 2 voltage is less than 0.1 volt for less than 1 seconds.

#### P0223

The ECM detects that the TP sensor 2 voltage is greater than 4.9 volts for less than 1 seconds.

### Action Taken When the DTC Sets

DTCs P0121, P0122, P0123, P0221, P0222, and P0223 are Type A DTCs.

### Conditions for Clearing the DTC

DTCs P0121, P0122, P0123, P0221, P0222, and P0223 are Type A DTCs.

### Diagnostic Aids

If a shared 5-volt reference circuit is shorted to ground or shorted to a voltage, other 5-volt reference circuits may be affected.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component 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

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Ignition ON, observe the DTC information with a scan tool. Verify that DTC P0642 or P0643 is not set.

⇒ | If any of the DTCs are set, refer to DTC P0642 or P0643.

2. Observe the scan tool TP Sensor parameters. Verify TP sensor 1 is 0.6-0.8 volts and TP sensor 2 is 4.1-4.3 volts.
3. Engine running, rapidly depress the accelerator pedal from the rest position to the WOT position and release pedal. Repeat the procedure several times. DTCs P0121, P0122, P0123, P0221, P0222, or P0223 should not set.
4. Slowly depress the accelerator pedal to WOT and then slowly return the pedal to closed throttle. Repeat the procedure several times. DTCs P0121, P0122, P0123, P0221, P0222, or P0223 should not set.
5. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the throttle body assembly.
2. Ignition OFF for at least 20 seconds, test for less than 10 ohms of resistance between the low reference circuit terminal 3 and ground.

⇒ | If greater than the specified range, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

Important: The 5-volt reference circuits are internally and externally connected at the ECM. Other component DTCs may be set. If other DTCs are set, review the electrical schematic and diagnose the applicable circuits and components.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 1 and ground.

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

⇒ | If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.

4. Verify the scan tool TP sensor voltage parameter is less than 0.3 volt.

⇒ | If greater than the specified range, test the appropriate signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

5. Install a 3A fused jumper wire between the appropriate signal circuit and the 5-volt reference circuit terminal 1. Verify the scan tool TP sensor voltage parameter is greater than 4.8 volts.

• | TP sensor 1 signal terminal 4

• | TP sensor 2 signal terminal 2

⇒ | If less than the specified range, test the appropriate signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

⇒ | If both TP sensor voltage parameters display greater than the specified range, test the signal circuits for a shorted together condition. If the circuit tests normal, replace the ECM.

6. If all circuits test normal, replace the throttle body assembly.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Throttle Body Assembly Replacement

• | Control Module References for engine control module replacement, setup, and programming