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P0221




DTC P0121-P0123 or P0221-P0223

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

DTC Descriptors
DTC P0121
- Throttle Position Sensor 1 Performance

DTC P0122
- Throttle Position Sensor 1 Circuit Low Voltage

DTC P0123
- Throttle Position Sensor 1 Circuit High Voltage

DTC P0221
- Throttle Position Sensor 2 Performance

DTC P0222
- Throttle Position Sensor 2 Circuit Low Voltage

DTC P0223
- Throttle Position Sensor 2 Circuit High Voltage

Diagnostic Fault Information





Typical Scan Tool Data





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 two independent signal circuits. The TP sensors have opposite functionality. TP sensor 1 signal voltage decreases from greater than 4 volts at idle to less than 1 volt at wide open throttle (WOT). TP sensor 2 signal voltage increases from less than 1 volt at idle to greater than 4 volts at WOT.

Conditions for Running the DTC

* The ignition is ON, with the engine OFF, or the engine is operating.
* The ignition voltage is greater than 7 volts.
* DTC P0121 runs continuously once the above conditions are met.

Conditions for Setting the DTC

P0121

The ECM detects TP sensor 1 disagrees greater than 9 percent from TP sensor 2 for greater than 1 second.

P0122

The ECM detects the TP sensor 1 signal voltage is less than 0.18 volt for greater than 1 second.

P0123

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

P0221

The TP sensor 2 disagrees greater than 9 percent from TP sensor 1 for greater than 1 second.

P0222

The ECM detects the TP sensor 2 signal voltage is less than 0.16 volts for greater than 1 second.

P0223

The ECM detects the TP sensor 2 signal voltage is greater than 4.9 volts for greater than 1 second.

Action Taken When the DTC Sets

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

Conditions for Clearing the DTC

* DTCs P0121 and P0221 are Type B DTCs.
* DTCs P0122, P0123, P0222, and P0223 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 ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Description and Operation

Throttle Actuator Control (TAC) System Description (Throttle Actuator Control (TAC) System Description)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing For Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

1. Ignition ON, verify that DTC P0697, P0698, or P0699 is not set.

• If a DTC is set, refer to DTC P0641-P0643, P0651-P0653, or P0697-P0699 (ECM) (ECM).

2. Clear the DTC Info with a scan tool.
3. Start the engine, observe the scan tool TP Sensor 1 and 2 voltage parameters. TP sensor 1 should be between 0.17-4.6 V and TP sensor 2 should be between 0.15-4.8 V.
4. Observe the scan tool TP sensor 1 and 2 parameters while performing the tests listed below. The TP sensor 1 and 2 parameter should display Agree.

* Rapidly depress the accelerator pedal from the rest position to the wide open throttle position (WOT) and release 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.

5. Observe the DTC Information with a scan tool. DTCs P0121, P0122, P0123, P0221, P0222, and P0223 should not set.
6. 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 Q38 throttle body.
2. Ignition OFF, remove the fuse that supplies B+ to terminal 56 X2 of the K20 ECM.

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

3. Test for less than 5 ohm between the low reference circuit terminal C 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 ECM.

4. Install fuse that supplies B+ to terminal 56 X2 of the K20 ECM.
5. Ignition ON, test for 4.8-5.2 V between the 5-volt reference circuit terminal E and ground.

• If less than the specified range, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
• If greater than the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.

6. Ignition ON, verify that the scan tool TP sensor 1 voltage parameter is less than 0.3 V.

• If greater than the specified value, test the signal circuit terminal D for a short to voltage. If the circuit tests normal, replace the K20 ECM.

7. Connect a 3 A fused jumper wire between the 5 volt reference circuit terminal E and the TP sensor 1 signal circuit terminal D. Verify the scan tool TP sensor 1 voltage 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 ECM.

8. Verify the scan tool TP sensor 2 voltage parameter is greater than 4.97 V.

• If less than the specified value, test the signal circuit terminal F for a short to ground. If the circuit tests normal, replace the K20 ECM.

Note: If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage.

9. Connect a 3 A fused jumper wire between the TP sensor 2 signal circuit terminal F and the low reference circuit terminal C. Verify the scan tool TP sensor 2 voltage parameter is less than 0.10 V.

• If greater than the specified value, test the signal circuit for an open/high resistance or for a short to voltage. If the circuit tests normal, replace the K20 ECM.

10. If all circuits test normal, replace the Q38 throttle body assembly.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Throttle Body Assembly Replacement (Removal and Replacement)
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming

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