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 P0122: Throttle Position (TP) Sensor 1 Circuit Low Voltage
DTC P0123: Throttle Position (TP) Sensor 1 Circuit High Voltage

### Diagnostic Fault Information

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

### Typical Scan Tool Data

#### TP Position Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: The engine is operating at idle. Parameter Normal Range: TP Position Sensor 0%
5-Volt Reference | 0% | 0% | 99%
Throttle Position Sensor Signal | 0% | 0% | 99%
Low Reference | -- | 99% | --

### Circuit/System Description

The throttle position (TP) sensor is used by the engine control module (ECM) to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with the following 3 circuits:

• | A 5-volt reference

• | A low reference

• | A signal

The ECM provides the TP sensor with 5 volts on the 5-volt reference circuit, and a ground on the low reference circuit. The TP sensor provides a signal voltage feedback that changes relative to throttle plate angle.

### Conditions for Running

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

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

### Conditions for Setting the DTC

#### P0122

The ECM detects that the TP sensor voltage is less than 0.3 volts for 2.5 seconds.

#### P0123

The ECM detects that the TP sensor voltage is greater than 4.9 volts for 2.5 seconds.

### Action Taken When the DTC Sets

DTCs P0122 and P0123 are Type A DTCs.

### Conditions for Clearing the DTC

DTCs P0122 and P0123 are Type A DTCs.

### 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 scan tool TP Sensor parameter. The reading should be between 0.4-4.5 volts.
2. Rapidly depress the accelerator pedal from the rest position to the wide open throttle position (WOT) and release pedal. Repeat the procedure several times. DTC P0122 or P0123 should not set.
3. Slowly depress the accelerator pedal to WOT and then slowly return the pedal to closed throttle. Repeat the procedure several times. DTC P0122 or P0123 should not set.
4. 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 TP sensor.
2. Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit terminal 1 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 2 and ground.

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

5. Install a 3A fused jumper wire between the signal circuit terminal 3 and the 5-volt reference circuit terminal 2. Verify the scan tool TP sensor voltage parameter is greater than 4.8 volts.

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

6. If all circuits test normal, test or replace the TP sensor.

### Component Testing

1. Ignition OFF, disconnect the harness connector at the TP sensor.
2. Test for 1,160-1,175 ohms between the 5-volt reference terminal 2 and the low reference terminal 1.

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

3. Sweep the TP sensor through the entire range while monitoring the resistance between the signal terminal 3 and the low reference terminal 1. The resistance should vary between 1,530 and 630 ohms without any spikes or dropouts.

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

4. Sweep the TP sensor through the entire range while applying 5 volts and ground to the applicable terminals. Test the voltage between the signal terminal 3 and the low reference terminal 1. The voltage should vary between 4.3-0.6 volts without any spikes or dropouts.

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Throttle Position Sensor Replacement

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