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 provide an overview of each diagnostic category.

### DTC Descriptors

DTC P0122: Throttle Position (TP) Sensor Circuit Low Voltage
DTC P0123: Throttle Position (TP) Sensor Circuit High Voltage

### Diagnostic Fault Information

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

### Typical Scan Tool Data

#### TP Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: The engine is operating in closed loop. Parameter Normal Range: TP Position Sensor 5%/4.2 Volts
5-Volt Reference | 6%/0.40 Volts | 6%/0.00 Volts | 14%/5.00 Volts
TP Sensor Signal | 6%/0.00 Volts | 6%/0.00 Volts | 6%/5.00 Volts
Low Reference | -- | 6%/5.00 Volts | --

### Circuit/System Description

The throttle body assembly contains a throttle position (TP) sensor. The TP sensor is mounted externally on the throttle body assembly. The TP sensor is a potentiometer which provides a signal voltage that changes relative to the throttle blade angle. The engine control module (ECM) supplies the TP sensor with a 5-volt reference circuit, a low reference circuit, and a signal circuit. The TP sensor signal voltage decreases from less than 1 volt at idle to more than 4 volts at wide open throttle (WOT).

### Conditions for Running the DTC

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

• | The DTCs runs continuously when the above condition is met.

### Conditions for Setting the DTC

Important: The scan tool displays a voltage near 0.0 volt. Do not use the scan tool voltage parameter to determine if there is a TP sensor condition.

#### P0122

The ECM detects that the TP sensor voltage is less than 0.14 volt for more than 5 seconds.

#### P0123

The ECM detects that the TP sensor voltage is more than 4.9 volts for more than 5 seconds.

### Action Taken When the DTC Sets

DTC P0122 and P0123 are Type A DTCs.

### Conditions for Clearing the DTC

DTC P0122 and P0123 are Type A DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

• | Engine Control Module Connector End Views

• | Engine Controls 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

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

### Circuit/System Verification

1. Start the engine, observe the TP Sensor voltage parameter with a scan tool. The parameters should be between 0.4-4.5 volts.
2. If the vehicle passes the Circuit/System Verification Test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector of the TP sensor.
2. Ignition ON, verify that the TP sensor voltage parameter is less than 0.3 volt.

⇒ | If greater than 0.3 volt, test the signal circuit of the TP sensor for a short to voltage. If the circuit/connections test normal, replace the ECM.

Important: The test lamp is used to load the circuit and may not illuminate.

3. Ignition ON, connect a test lamp between the 5-volt reference circuit of the TP sensor and a good ground.

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.

4. Test for 4.8-5.2 volts between the 5-volt reference circuit of the TP sensor and a good ground.

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

⇒ | If greater than 5.2 volts, test the 5-volt reference circuit of the TP sensor for a short to voltage. If the circuit/connections test normal, replace the ECM.

5. Ignition ON, test for less than 0.2 volt between the low reference circuit of the TP sensor and a good ground.

⇒ | If greater than 0.2 volt, test the low reference circuit of the TP sensor for a short to voltage. If the circuit/connections test normal, replace the ECM.

6. Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit of the TP sensor and a good ground.

⇒ | If greater than 5 ohms, test the low reference circuit of the TP sensor for an open/high resistance. If the circuit/connections test normal, replace the ECM.

7. Ignition ON, install a 3-amp fused jumper wire between the signal circuit and the 5-volt reference circuit of the TP sensor to verify that the TP sensor voltage parameter is greater than 4.8 volts.

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

8. If all circuits/connections test normal, test or replace the TP sensor.

### Component Testing

1. Turn OFF the ignition.
2. Measure for 5150-5350 ohms between the 5-volt reference and the low reference terminals of the TP sensor .

⇒ | If the resistance is not within the specified range, replace the TP sensor.

3. Measure the resistance between the signal terminal and the low reference terminal of the TP sensor. Slowly sweep the TP sensor through the entire range several times. The resistance should vary between 2500-6800 ohms without any spikes or dropouts.

⇒ | If the resistance is not within the specified range or is erratic, replace the TP sensor.

4. Apply 5 volts and ground to the applicable terminals of the TP sensor, and measure the voltage between the signal and the low reference terminals. Slowly sweep the TP sensor through the entire range several times. The voltage should vary between 0.6-4.7 volts without any spikes or dropouts.

⇒ | If the voltage is not within the specified range or is erratic, replace the TP sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Throttle Position Sensor Replacement

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