Diagnostic Instructions

DTC Descriptor

DTC P1516 00: Throttle Actuator Control (TAC) Motor Control Circuit

DTC P2101 00: Control Module Throttle Actuator Position Performance

DTC P2119 00: Throttle Closed Position Performance

DTC P2176 00: Minimum Throttle Position Not Learned

Diagnostic Fault Information

Circuit	Short to Ground	Open High Resistance	Short to Voltage	Signal Performance
Motor Control 1	P1516 00, P2101 00, P2176 00	P1516 00, P2101 00, P2176 00	P1516 00, P2101 00, P2176 00	P1516 00, P2101 00, P2176 00
Motor Control 2	P1516 00, P2101 00, P2176 00	P1516 00, P2101 00, P2176 00	P1516 00, P2101 00, P2176 00	P1516 00, P2101 00, P2176 00

Circuit/System Description

The engine control module (ECM) is the control center for the throttle body throttle actuator control (TAC) system. The ECM determines the drivers intent and then calculates the appropriate throttle response. The ECM achieves throttle positioning by providing a pulse width modulated voltage to the throttle body (TAC) motor. The throttle body (TAC) motor system uses the following circuits:

Two processors are also used to monitor the throttle body (TAC) motor system data. Both processors are located within the ECM. Both processors monitor each others data to verify that the indicated throttle position is correct.

Conditions for Running the DTC

P1516 00 or P2101 00

P2119 00

P2176 00

Conditions for Setting the DTC

P1516 00

The indicated throttle position does not match the predicted throttle position for more than 0.5 s.

P2101 00

The indicated throttle position does not match the predicted throttle position for more than 0.3 s.

P2119 00

The ECM determines that the throttle blade did not return to the rest position within 720 ms.

P2176 00

The difference between the predicted and the actual throttle position is more than a calibrated amount for more than 1.5 s.

Action Taken When the DTC Sets

Conditions for Clearing the DTC

Diagnostic Aids

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

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, engine OFF, use a scan tool to observe the throttle position sensor 1 indicated position. Throttle position should increase as pedal is applied and decrease as pedal is released. When no accelerator pedal activity is detected, the throttle position will return to the spring loaded default position.

Note: A low voltage condition may set this DTC.

2. Review the freeze frame/failure records and ensure sufficient ignition voltage was present when the DTC was set.

⇒	If voltage was low, verify with the owner that the battery was not discharged. If the battery has not been discharged, refer to Power Mode Mismatch

3. 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.

Circuit/System Testing

1. Inspect the Q38 Throttle Body for the following conditions:

•	A throttle blade that is not in the rest position

•	A throttle valve that is binding open or closed

•	A throttle valve that opens or closes without spring pressure

⇒	If a condition is found, replace the Q38 Throttle Body.

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

2. Ignition OFF, disconnect the harness connector of the Q38 Throttle Body.
3. Ignition ON, test for greater than 9 V on the Q38 Throttle Body motor control circuit X1 pin A or Q38 Throttle Body motor control circuit terminal B (X1).

⇒	If less than the specified range, test the Q38 Throttle Body motor control circuit X1 pin A or Q38 Throttle Body motor control circuit terminal B (X1) circuits for a short to ground, or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

4. Ignition ON, probe the Q38 Throttle Body motor control circuit terminal A (X1) or Q38 Throttle Body motor control circuit terminal B (X1) with a test lamp connected to ground. Verify the test lamp does not illuminate.

⇒	If the test lamp illuminates, test the Q38 Throttle Body motor control circuit  terminal A (X1) or Q38 Throttle Body motor control circuit terminal B (X1) for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

5. Set the DMM to AC hz on the 400 mV scale. Engine idling, test for greater than 2000 AC hz between Q38 Throttle Body motor control circuit terminal A (X1) or Q38 Throttle Body motor control circuit terminal B (X1) and ground while commanding the engine speed to 1950 RPM with a scan tool.

⇒	If less than the specified value, replace the K20 Engine Control Module (ECM).

6. If all circuits test normal, replace the Q38 Throttle Body.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.