Buick Regal: DTC P1516, P2101, P2119, or P2176

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 P1516

Throttle Actuator Control (TAC) Module Throttle Actuator Position Performance

DTC P2101

Throttle Actuator Position Performance

DTC P2119

Throttle Closed Position Performance

DTC P2176

Minimum Throttle Position Not Learned

Diagnostic Fault Information

Circuit/System Description

The Throttle Body Assembly contains a contact-less inductive throttle position sensing element that is managed by a customized integrated circuit. The throttle position sensor is mounted within the Throttle Body Assembly and is not serviceable. The Engine Control Module (ECM) supplies the throttle body with a 5 V reference circuit, a low reference circuit, an H-bridge motor directional control circuit, and an asynchronous signal/serial data circuit. The asynchronous signal means communication is only going from the throttle body to the ECM. The throttle body cannot receive data from the ECM over the signal/serial data circuit. The throttle position sensor provides a signal voltage that changes relative to throttle blade angle. The customized integrated circuit translates the voltage based position information into serial data using the Society of Automotive Engineers (SAE) J2716 Single Edge Nibble Transmission (SENT) protocol. The throttle position sensor information is transmitted between the throttle body and the ECM on the signal/serial data circuit. The ECM decodes the serial data into a representation of voltage signals that are occurring in the throttle body. The information is then displayed on a scan tool as the voltage inputs from TP sensors 1 and 2.

The ECM controls the throttle valve by applying a varying voltage to the control circuits of the throttle actuator control (TAC) motor. The ECM monitors the duty cycle that is required to actuate the throttle valve. The ECM monitors the throttle position sensor signal/serial data circuit to determine the actual throttle valve position.

Conditions for Running the DTC

P1516

• DTC P0606, P1682 is not set.
• The run/crank or powertrain relay voltage is greater than 6.41 V and reduced power is not active.
• DTC P1516 runs continuously when the above conditions are met.

P2101

• DTC P0606, P1682 is not set.
• The run/crank or powertrain relay voltage is greater than 6.41 V and reduced power is not active.
• The engine is running or the following conditions are met:
  • The engine is not running.
  • The ignition voltage is greater than 11 V.
  • The TAC system is not in the Battery Saver mode.
  • The ECM is commanding the throttle.
  • The ECM has learned the minimum throttle position.
• DTC P2101 runs continuously when the above conditions are met.

P2119

• DTCs P0122, P0123, P0222, P0223, or P06A3 is not set.
• The run/crank or powertrain relay voltage is greater than 5.5 V and reduced power is not active.
• The system is not in the Battery Save mode.
• The ECM is not commanding the throttle.
• DTC P2119 runs continuously when the above conditions are met.

P2176

• The run/crank or powertrain relay voltage is greater than 6.4 V and reduced power is not active.
• DTC P2176 runs continuously when the above conditions are met.

Conditions for Setting the DTC

P1516

The ECM detects an unstable throttle position for greater than 1 s.

P2101

• The ECM detects the actual throttle position does not match the predicted throttle position for greater than 1 s.

  OR

• The ECM detects the throttle control is driving the throttle in the incorrect direction or exceed the reduced power limit.

P2119

The ECM determines that the throttle blade did not return to the rest position within 1 s.

P2176

The ECM detects that both throttle position sensors were greater than a predetermined voltage during the minimum throttle learn procedure for greater than 2 s.

Action Taken When the DTC Sets

• DTC P1516 is a Type B DTC.
• DTCs P2101 and P2176 are Type A DTCs.
• DTC P2119 is a Type C DTC.
• The ECM commands the TAC system to operate in the Reduced Engine Power mode.
• A message center or an indicator displays Reduced Engine Power.
• Under certain conditions, the control module commands the engine OFF.

Conditions for Clearing the MIL/DTC

• DTC P1516 is a Type B DTC.
• DTCs P2101 and P2176 are Type A DTCs.
• DTC P2119 is a Type C DTC.

Diagnostic Aids

• Depending on the Start Up ECT, the Desired Throttle Position percentage maybe greater or less than the Throttle Position with the TAC motor at rest. When the ignition is initially turned ON, or when the engine is cranking or running the Desired and Actual Throttle positions should closely match.
• Inspect for a condition in which the throttle valve may have been held open. For example, ice may have formed in the throttle bore causing the throttle valve not to close.
• A high resistance condition on the throttle position and throttle actuator control circuits could cause a DTC to set.
• A low battery condition may cause a DTC to set.

Reference Information

Schematic Reference

Engine Controls Wiring Schematics (LTG)

Connector End View Reference

Component Connector End View Index

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.

NOTE: A low battery voltage or charging system condition may cause a DTC to set.

2. Verify DTC P0121, P0122, P0123, P0222, P0223, P0562, P0621, P0622, or P2135 is not set.

• If any of the DTCs are set

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

• Go to next step: If none of the DTCs are set

3. Verify the scan tool Throttle Body Idle Air flow Compensation parameter is less than 90 %.

• If 90 % or greater

Refer to Throttle Body Cleaning.

• Go to next step: If less than 90 %

4. Clear the DTCs with a scan tool.

5. Ignition OFF and all vehicle systems OFF. It may take up to 2 min for all vehicle systems to power down.

6. Ignition ON.

7. Verify the scan tool TAC Motor parameter displays Enabled while slowly depressing the accelerator pedal.

• If Enabled is not displayed

Refer to Circuit/System Testing.

• Go to next step: If Enabled is displayed

8. Verify DTC P1516, P2101, P2119, or P2176 is not set.

• If any of the DTCs are set

Refer to Circuit/System Testing.

• Go to next step: If none of the DTCs are set

NOTE: If there is a condition with the throttle body, the TAC Motor Command parameter will go to 99 % for a predetermined amount of time and then a DTC sets. Once a DTC is set, the TAC Motor Command parameter will go to 0 % and the TAC Motor parameter will display Disabled.

9. Verify the scan tool TAC Motor parameter displays Enabled while performing the Throttle Sweep Test with a scan tool.

• If Enabled is not displayed

Test or replace the Q38 Throttle Body Assembly.

• Go to next step: If Enabled is displayed

10. 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.

11. Verify the DTC does not set.

• If the DTC sets

Refer to Circuit/System Testing.

• Go to next step: If the DTC does not set

12. All OK.

Circuit/System Testing

1. Ignition OFF.

WARNING: Turn OFF the ignition before inserting fingers into the throttle bore.

Unexpected movement of the throttle blade could cause personal injury.

2. Verify the conditions listed below do not exist with the Q38 Throttle Body:

NOTE:

• The rest position is defined as the actual Throttle Position percentage when the ignition is OFF or with the ignition ON for greater than 30 seconds.
• When the ignition is OFF, spring tension should hold the throttle plate in the rest position. You should be able to open the throttle plate to wide open throttle (WOT) or push the throttle plate to the fully closed position. In each case, the throttle plate should return to the rest position without assistance.

• A throttle blade that is not in the rest position
• A throttle blade that is binding open or closed
• A throttle blade that is free to move open or closed without spring pressure
• If a condition is found

Replace the Q38 Throttle Body.

• Go to next step: If a condition is not found

NOTE: Disconnecting the throttle body harness connector may cause additional DTCs to set.

3. Disconnect the harness connector at the Q38 Throttle Body Assembly, ignition ON.

NOTE: The test lamp may illuminate briefly when the ignition switch is turned on, but should not remain illuminated.

4. Verify that a test lamp does Not illuminate continuously between each motor control circuit listed below and ground.

• TAC Motor Control Closed circuit terminal 1
• TAC Motor Control Open circuit terminal 2
• If the test lamp is always ON

1. Ignition OFF, disconnect the harness connector X2 at the K20 Engine Control Module, ignition ON
2. Test for less than 1 V between the motor control 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.

• Go to next step: If the test lamp is always OFF

5. Verify that a test lamp does not illuminate between each motor control circuit listed below and B+.

• TAC Motor Control Closed circuit terminal 1
• TAC Motor Control Open circuit terminal 2
• If the test lamp illuminates

1. Ignition OFF, disconnect the harness connector X2 at the K20 Engine Control Module.
2. Test for infinite resistance between the control circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the K20 Engine Control Module.

• Go to next step: If the test lamp does not illuminate

6. Ignition OFF, set the DMM to the 40 V scale, select the Min/Max Recording Mode, and set the Peak Min/Max response time to 1 ms.

NOTE:

• The test lamp must be connected to circuit before turning ignition on or incorrect diagnosis may occur.
• The ignition must be OFF and the ECM completely powered down before testing each circuit or a lower voltage will be recorded. It may take up to 2 min for all vehicle systems to power down.
• The DMM Min/Max Recording Mode and the response time of 1 ms must be reset after testing each circuit or a lower voltage will be recorded.

7. Verify the Max voltage is within 3 V of B+ while using DMM Min/Max Recording Mode function on each control circuit listed below as the ignition is turned ON.

• TAC Motor Control Closed circuit terminal 1
• TAC Motor Control Open circuit terminal 2
• If not within 3 V of B+

1. Ignition OFF, disconnect the harness connector X2 at the K20 Engine Control Module.
2. Test for less than 2 Ω in the control 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.

• Go to next step: If within 3 V of B+

8. Replace the Q38 Throttle Body.

Repair Instructions

• Throttle Body Assembly Replacement
• Control Module References for ECM replacement, programming, and setup

Repair Verification

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 min for all vehicle systems to power down.

5. Ignition ON.

6. Verify the scan tool TAC Motor parameter displays Enabled while performing the Throttle Sweep Test with a scan tool.

• If Enabled is not displayed

Test or replace the Q38 Throttle Body Assembly.

• Go to next step: If Enabled is 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.

• Go to next step: If DTC does not set

8. All OK.

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