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 Descriptor

DTC P0122 00: Throttle Position Sensor 1 Circuit Low Voltage
DTC P0123 00: Throttle Position Sensor 1 Circuit High Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
5-Volt Reference | P0641 | P0122 | P0641 | --
Signal | P0122 | P0123 | P0123 | --
Low Reference | -- | P0123 | P0123 | --

### Typical Scan Tool Data

#### Intake Air Flow Valve Position Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: The engine is operating in closed loop Parameter Normal Range: Intake Air Flow Valve Position Sensor 4.2 V
5-Volt Reference | 0.0 V | 0.0 V | 5.0 V
Intake Air Flow Valve Position Sensor | 0.0 V | 0.0 V | 5.0 V
Low Reference | 0.0 V | 0.0 V | --

### Circuit/System Description

The throttle body assembly contains a throttle position sensor. The throttle position sensor is mounted to the throttle body assembly and are not serviceable. The throttle position sensor provide a signal voltage that changes relative to throttle blade angle. The engine control module (ECM) supplies the throttle position sensor with a common 5-volt reference circuit , a common low reference circuit, and a signal circuit. The throttle position sensor signal voltage decreases from greater than 4 V at idle to less than 1 V at wide open throttle.

### Conditions for Running the DTC

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

• | The ignition voltage is greater than 7 V.

### Conditions for Setting the DTC

#### P0122

The ECM detects the throttle position sensor signal voltage is less than 0.18 V for greater than 1 s or a cumulative of 10 s.

#### P0123

The ECM detects the throttle position sensor signal voltage is greater than 4.6 V for greater than 1 s or a cumulative of 10 s.

### Action Taken When the DTC Sets

DTCs P0121 and P0123 are Type B DTCs.

### Conditions for Clearing the DTC

DTCs P0121 and P0123 are Type B DTCs.

### Diagnostic Aids

If there is a condition with the throttle body sensors the ECM defaults to reduced power mode for the entire ignition cycle, even if the condition is corrected.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### 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. DTC P0641 should not be set.

⇒ | If a DTC is set, refer to Control Module References.

2. Clear the DTC information with a scan tool.
3. 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 Q38 Throttle Body harness connector.

Note: The control module or the sensor may be damaged if the circuit is shorted to battery positive voltage.

2. Test for less than 5 Ω between the low reference circuit terminal 3 (X1) 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 K20 Engine Control Module (ECM).

3. Ignition ON, test for 4.8-5.2 V between the 5-volt reference circuit terminal 1 (X1) 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 K20 Engine Control Module (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 K20 Engine Control Module (ECM).

4. Ignition ON, verify that the scan tool Intake Air Flow Valve Position Sensor voltage parameter is less than 0.3 V.

⇒ | If greater than the specified value, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

5. Connect a 3 A fused jumper wire between the 5-volt reference circuit terminal 1 (X1) and the signal circuit terminal 5 (X1). Verify the scan tool Intake Air Flow Valve Position Sensor parameter is greater than 4.89 V.

⇒ | If less than the specified value, test the signal circuit for an open/high resistance or for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

6. If all circuits test normal, replace the Q38 Throttle Body.

### 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