GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2008 🢒 Vivant 🢒 HVAC 🢒 HVAC - Automatic 🢒 DTC 021 or 022

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 021: Throttle Position (TP) Sensor Circuit High Voltage

DTC 022: Throttle Position (TP) Sensor Circuit Low Voltage

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 Setting the DTC

021

    • DTCs 033 and 034 are not set.
    • The engine speed is less than 3,000 RPM.
    • The manifold absolute pressure (MAP) reading is less than 85 kPa (12.3 psi).
    • The TP sensor reading is greater than 240 counts.
    • The DTC runs continuously once the above condition is met for 2 seconds.

022

    • DTCs 033 and 034 are not set.
    •  The TP sensor reading is less than 11 counts for at least 2 seconds.
    • The DTC runs continuously once the above condition is met for 2 seconds.

Reference Information

Schematic Reference

Engine Controls Schematics

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Engine running, observe the scan tool TP Sensor voltage parameter. The readings should be between 0.4-4.5 volts.

Circuit/System Testing
  1. Ignition OFF, disconnect the harness connector at the TP sensor.
  2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal B and ground.
    3. ⇒If greater than the specified range, test the low reference circuit for 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 A and ground.
    4. ⇒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.
    5. ⇒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 C and the 5-volt reference circuit terminal A. Verify the scan tool TP sensor voltage parameter is greater than 4.8 volts.
    6. ⇒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 5150-5350 ohms between the 5-volt reference terminal  A and the low reference terminal B.
    3. ⇒If not within the specified range, replace the TP sensor.
  3. Sweep the TP sensor through the entire range several times while monitoring the resistance between the signal terminal C and the low reference terminal B. The resistance should vary between 2500-6800 ohms without any spikes or dropouts.
    4. ⇒If not within the specified range or is erratic, replace the TP sensor.
  4. Sweep the TP sensor through the entire range several times while applying 5-volts and ground to the applicable terminals. Test the voltage between the signal terminal C and the low reference terminal B. The voltage should vary between 0.6-4.7 volts without any spikes or dropouts.
    5. ⇒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 ECM replacement, setup, and programming.