• 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.

The assembly has several functions:

The throttle valve is actuated by a bidirectional DC motor. A spring pulls the valve to a rest or default position, in which the valve is almost closed. The throttle actuator motor can push against the force of the spring to open or close the valve. The more current flow through the motor, the more the valve moves.

The throttle body contains a contactless inductive position sensor. A fixed transmitter coil excites a movable rotor, which in turn induces a current in a fixed receiver coil. The current varies with the angle of the rotor. Electronics inside the sensor convert the current into digital data which is transmitted via a serial data circuit to the ECM.

The engine control module (ECM) determines the driver's intent based on input from the accelerator pedal position sensors, then calculates the appropriate throttle response based on the throttle position sensors.

• DTCs P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0335, or P0336 is not set.
• The engine speed is between 500–6,800 RPM.
• The engine coolant temperature (ECT) is −7 to +126°C (19–259°F).
• The intake air temperature (IAT) is −20 to +125°C (−4 to +257°F).
• The DTC runs continuously when the above conditions are met.

• DTC P06A3 is not set.
• The run/crank or powertrain relay voltage is greater than 6.41 V and reduced power is not active.
• The DTCs run continuously when the above condition are met.

• DTC P06A3 is not set.
• The run/crank voltage is greater than 6.41 V.
• The DTCs run continuously once the above conditions are met.

• DTCs P0122, P0123, P0222, P0223, or P06A3 are not set.
• The run/crank or powertrain relay voltage is greater than 6.41 V and reduced power is not active.
• The DTC runs continuously when the above conditions are met.

The ECM detects that the throttle position sensor 1 voltage is stuck in range for greater than 1 s.

The ECM detects the throttle position sensor 1 signal voltage is less than 0.32 V for greater than 1 s.

The ECM detects the throttle position sensor 1 signal voltage is greater than 4.75 V for greater than 1 s.

The ECM detects the throttle position sensor 2 signal voltage is less than 0.25 V for greater than 1 s.

The ECM detects the throttle position sensor 2 signal voltage is greater than 4.6 V for greater than 1 s.

The ECM detects a low voltage circuit condition on the throttle position sensor signal circuit for greater than 1 s.

The ECM detects a high voltage circuit condition on the throttle position sensor signal circuit for greater than 1 s.

The ECM detects an incorrect message was received over the throttle position sensor signal circuit for greater than 1 s.

The ECM detects that throttle position sensors 1 and 2 disagree greater than 7–10 percent for greater than 1 s.

• DTCs P0121 is a Type B DTC.
• DTCs P0122, P0123, P0222, P0223, P16A0, P16A1, P16A2, and P2135 are Type A DTCs.
• The ECM commands the throttle actuator control (TAC) system to operate in a Reduced Engine Power mode.
• A message center or an indicator displays Reduced Engine Power.
• Under certain conditions, the ECM commands the engine OFF.

• DTCs P0121 is a Type B DTC.
• DTCs P0122, P0123, P0222, P0223, P16A0, P16A1, P16A2, and P2135 are Type A DTCs.

• A high resistance condition on the throttle position and throttle actuator control circuits could cause a DTC to set.
• If the accelerator pedal is pressed to the wide open throttle position, the throttle blade angle or Throttle Position angle is limited to less than 40 percent.

Engine Controls Schematics

Master Electrical Component List

Throttle Actuator Control (TAC) System Description

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

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Control Module References for scan tool information

1. If you were sent here from DTC P0068, P0101, P0106, or P1101 refer to Circuit/System Testing.
2. Ignition ON.
3. Verify that DTC P0601–P0606, P06A3, and P16F3 is not set.
• If any of the DTCs are set

  Refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.

• If none of the DTCs are set
4. Verify the scan tool Throttle Body Idle Air flow Compensation parameter is less than 90 %.
• If 90 % or greater

  Refer to Throttle Body Cleaning and Inspection.

• If less than 90 %
5. Verify that DTC P0122, P0123, P0222, P0223, P16A0, P16A1, P16A2, or P2135 are not set.
• If DTC P0122, P0123, P0222, P0223, or P2135 are the only DTCs set

  Test or replace the Q38 Throttle Body Assembly.

• If DTC P16A0, P16A1, or P16A2 is set with any of the DTCs

  Refer to Circuit/System Testing.

• If none of the DTCs are set
6. Verify the Throttle Position Sensors 1 and 2 Agree/Disagree parameter displays Agree while performing the Throttle Sweep Test with a scan tool.
• If Agree is not displayed

  Test or replace the Q38 Throttle Body Assembly.

• If Agree is displayed
7. Verify DTC P0122, P0123, P0222, P0223, P16A0, P16A1, P16A2, and P2135 is not set.
• If a DTC is set

  Refer to Circuit/System Testing.

• If a DTC is not set
8. Determine the current vehicle testing altitude.
9. Verify the scan tool MAP Sensor pressure parameter is within range specified in the Altitude Versus Barometric Pressure table.
• The MAP Sensor pressure is not in range

  Refer to DTC P0106.

• The MAP Sensor pressure is within range
10. Engine idling.
11. Verify the scan tool MAP Sensor pressure parameter is between 26–52 kPa (3.8–7.5 psi) and changes with accelerator pedal input.
• If not between 26–52 kPa (3.8–7.5 psi) or does not change

  Refer to DTC P0106.

• If between 26–52 kPa (3.8–7.5 psi) and changes
12. Verify the scan tool MAF Sensor g/s parameter changes smoothly and gradually as the engine speed is increased and decreased while performing the actions listed below.
1. Engine idling
2. Perform the scan tool snapshot function.
3. Increase the engine speed slowly to 3,000 RPM and then back to idle.
4. Exit from the scan tool snapshot and review the data.
5. Observe the MAF Sensor parameter frame by frame with a scan tool.
• The MAF Sensor parameter does not change smoothly and gradually

  Refer to DTC P0101.

• The MAF Sensor parameter changes smoothly and gradually
13. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
14. Verify the DTC does not set.
• If the DTC sets

  Refer to Circuit/System Testing.

• If the DTC does not set
15. All OK.

Note: Disconnecting the throttle body harness connector causes additional DTCs to set.

1. Ignition OFF, and all vehicle systems OFF, disconnect the harness connector at Q38 Throttle Body Assembly. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 5 Ω between the low reference circuit terminal 4 and ground.
• If 5 Ω or greater
1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for less than 2 Ω in the low reference circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, replace the K20 Engine Control Module.
• If less than 5 Ω
3. Ignition ON.
4. Test for 4.8–5.2 V between the 5 V reference circuit terminal 5 and ground.
• If less than 4.8 V
1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the 5 V reference circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 Ω in the 5 V reference circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, replace the K20 Engine Control Module.
• If greater than 5.2 V
1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module, ignition ON.
2. Test for less than 1 V between the 5 V reference circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K20 Engine Control Module.
• If between 4.8–5.2 V
5. Test for 3.5 to 12 V between the test points:Serial Data circuit terminal 3&Ground
• If less than 3.5 V and does not fluctuate
1. Ignition/Vehicle » Off
2. Disconnect the electrical connector:K20 Engine Control Module
3. Test for infinite resistance between the test points:Serial Data circuit terminal 3@Component harness&Ground
• If less than infinite resistance » Repair the short to ground on the circuit.
• If infinite resistance
4. Test for less than 2 Ω between the test points:Serial Data circuit terminal 3The other end of the circuit
• If 2 Ω or greater » Repair the open/high resistance in the circuit.
• If less than 2 Ω » Replace the component:K20 Engine Control Module
• If greater than 12 V and does not fluctuate
1. Ignition/Vehicle » Off
2. Disconnect the electrical connector:K20 Engine Control Module
3. Ignition » On / Vehicle » In Service Mode
4. Test for less than 1 V between the test points:Serial Data circuit terminal 3@Component harness&Ground
• If 1 V or greater » Repair the short to voltage on the circuit.
• If less than 1 V » Replace the component:K20 Engine Control Module
• If between 3.5 and 12 V and fluctuates
6. Test or replace the component:Q38 Throttle Body

• Throttle Body Assembly Replacement
• Control Module References for engine control module replacement, programming, and setup

1. Install any components that have been removed or replaced during diagnosis.
2. Perform any adjustments, programming or setup procedures that are required when a component is removed or replaced.
3. Clear the DTCs with a scan tool.
4. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down.
5. Ignition ON.
6. Verify the Throttle Position Sensors 1 and 2 Agree/Disagree parameter displays Agree while performing the Throttle Sweep Test with a scan tool.
• If Agree is displayed

  Test or replace the Q38 Throttle Body Assembly.

• If Agree is not displayed
7. If the repair was related to a DTC, duplicate the Conditions for Running the DTC and use the Freeze Frame/Failure Records, if applicable, in order to verify the DTC does not set.
• If DTC sets

  Refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.

• If DTC does not set
8. All OK.