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 P1121: Throttle Position (TP) Sensor Circuit Intermittent High Voltage
DTC P1122: Throttle Position (TP) Sensor Circuit Intermittent Low Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
5-Volt Reference | P0122, P1122 | -- | P0122, P1122 | P0123, P1121 | --
Throttle Position Sensor Signal | P0122, P1122 | -- | P0122, P1122 | P0123, P1121 | --
Low Reference | -- | -- | P0123, P1121 | -- | --

### 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 DTCs

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

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

### Conditions for Setting the DTC

#### P1121

The ECM detects that the TP sensor voltage is greater than 4.9 volts intermittently for greater than 2 seconds during a 60 second time period.

#### P1122

The ECM detects that the TP sensor voltage is less than 0.14 volt intermittently for greater than 2 seconds during a 60 second time period.

### Action Taken When the DTC Sets

DTCs P1121 and P1122 are Type C DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P1121 and P1122 are Type C 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. Engine runing, observe the DTC information with a scan tool. DTCs P0122 or P0123 should not set.

⇒ | If any DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.

2. Operate the vehicle within the conditions for running the DTC. DTCs P1121 or P1122 should not set.
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

Engine running, observe the scan tool throttle position (TP) sensor parameter while moving the related wiring harness and harness connectors. The reading should not change abruptly.

⇒ | If the reading changes abruptly, repair the wiring harness and harness connectors.

### 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 and the low reference terminal 1.

• | TP Sensor 1 and Sensor 2 with TAC 5-volt reference terminal 4

• | TP Sensor 1 without TAC 5-volt reference terminal 2

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

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

• | TP Sensor 1 with TAC signal terminal 2

• | TP Sensor 2 with TAC signal terminal 3

• | TP Sensor 1 without TAC signal terminal 3

⇒ | 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 and the low reference terminal 1. The voltage should vary between 4.3-0.6 volts without any spikes or dropouts.

• | TP Sensor 1 with TAC signal terminal 2

• | TP Sensor 2 with TAC signal terminal 3

• | TP Sensor 1 without TAC signal terminal 3

⇒ | If 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 engine control module replacement, setup, and programming