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
DTC P2135: Throttle Position (TP) Sensor 1-2 Correlation

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
5-Volt Reference | P0122, P0222, P2127 | P0121, P0122, P0222, P2119, P2135 | P0223, P2119, P2128, P2138 | P0121, P0221
TP Sensor Signal 1 | P0122 | P0122, P2135 | P0123 | P0121
TP Sensor Signal 2 | P0222 | P0222 | P0223, P0638, P2128, P2138 | P0221
Low Reference | -- | P0121, P0123, P0221, P0223 | P0123, P0223* | P0121, P0221
* Internal ECM or TP sensor damage may occur if the circuit is shorted to B+

### 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%/0.4 Volt | 0%/0 Volt | 14%/5 Volts
TP Sensor Signal | 6%/0 Volt | 3%/0 Volt | 6%/5 Volts
Low Reference | -- | 6%/5 Volt | --

### 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, P2135

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

• | The engine temperature is greater than 60°C (140°F).

• | The ignition 1 voltage is greater than 7 volts.

• | The TP sensor 1 voltage is between 0.1-4.6 volts.

• | The DTCs run once per ignition cycle the above conditions are met.

#### P0122, P0123, P0222, and P0223

• | The engine speed is greater than 1200 RPM.

• | The ignition 1 voltage is greater than 7 volts.

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

#### P0221

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

• | The ignition 1 voltage is greater than 7 volts.

• | The TP sensor 2 voltage is between 0.1-4.8 volts.

• | The DTC runs continuously once the above conditions are met.

### Conditions for Setting the DTC

#### P0121 and P2135

• | The TP sensor 1 disagrees greater than 6 percent from TP sensor 2.

| OR

• | TP sensor 1 disagrees greater than 9 percent from the predicted value. Either condition exists for greater than 4 seconds.

#### P0122

The ECM detects the TP sensor 1 signal voltage is less than 0.2 volts.

#### P0123

The ECM detects the TP sensor 1 signal voltage is greater than 4.6 volts.

#### P0221

• | The TP sensor 1 disagrees greater than 6 percent from TP sensor 2.

| OR

• | TP sensor 2 disagrees greater than 6 percent from the predicted value.

#### P0222

The ECM detects the TP sensor 2 signal voltage is less than 0.2 volts.

#### P0223

The ECM detects the TP sensor 2 signal voltage is less than 0.2 volts.

### Action Taken When the DTC Sets

DTCs P0121, P0122, P0123, P0221, P0222, P0223, and P2135 are Type A DTCs.

### Conditions for Clearing the DTC

DTCs P0121, P0122, P0123, P0221, P0222, P0223, and P2135 are Type A DTCs.

### Diagnostic Aids

If there is a condition with the TP 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

#### 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, clear the DTC Information with a scan tool.
2. Engine running, observe the scan tool TP Sensor 1 and 2 voltage parameters. TP sensor 1 and TP sensor 2 should be between 0.4-1.0 volt.
3. Observe the scan tool TP sensor 1 and 2 parameter while performing the following tests:

• | Rapidly depress the accelerator pedal from the rest position to the wide open throttle position (WOT) and release the pedal. Repeat the procedure several times.

• | Slowly depress the accelerator pedal to WOT and then slowly return the pedal to closed throttle. Repeat the procedure several times.

• | The scan tool TP sensor 1 and 2 parameter should display Agree.

4. Observe the DTC Information with a scan tool. DTCs P0121, P0122, P0123, P0221, P0222, P0223, and P2135 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, and the MAIN fuse removed, disconnect the harness connector at the throttle body .
2. Ignition OFF, test for 5 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.

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

⇒ | 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. Ignition ON, verify each of the scan tool TP sensor voltage parameters 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. Connect a 3A fused jumper wire between the 5 volt reference circuit and each of the TP sensor signal circuits.

• | TP sensor 1 circuit terminal 2

• | TP sensor 2 circuit terminal 4

6. Observe each of the scan tool TP sensor voltage parameters. Both TP sensor voltage parameters should display 5 volts.

⇒ | 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.

7. 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