Diagnostic Instructions

DTC Descriptor

DTC P2100 00: Throttle Actuator Control (TAC) Motor Control Circuit

DTC P2101 00: Control Module Throttle Actuator Position Performance

DTC P2108 00: Throttle Actuator Control (TAC) Module Performance

DTC P2119 00: Throttle Closed Position Performance

DTC P2176 00: Minimum Throttle Position Not Learned

Diagnostic Fault Information

Circuit	Short to Ground	High Resistance	Open	Short to Voltage	Signal Performance
Motor Control 1	P2101 00, P2176 00	P2101 00, P2176 00	P2101 00, P2176 00	P2101 00, P2176 00	P2101 00, P2176 00
Motor Control 2	P2101 00, P2176 00	P2101 00, P2176 00	P2101 00, P2176 00	P2101 00, P2176 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 other's data to verify that the indicated throttle position is correct.

Conditions for Running the DTC

P2100 00

P2101 00, P2119 00, P2176 00

P2108 00

Conditions for Setting the DTC

P2100 00

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

P2101 00, P2108 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

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.

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.
2. 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 0 V between the Q38 Throttle Body Motor Control Circuit terminal 3 (X1) and ground.

⇒	If greater than 0 V, test the Q38 Throttle Body Motor Control Circuit terminal 3 (X1) for a short to voltage.

⇒	If the circuit tests normal, replace the K20 Engine Control Module (ECM).

4. Ignition ON, test for 0 V between the Q38 Throttle Body Motor Control Circuit terminal 5 (X1) and ground.

⇒	If greater than 0 V, test the Q38 Throttle Body Motor Control Circuit 5 (X1) for a short to voltage.

⇒	If the circuit tests normal, replace the Q38 Throttle Body.

5. Ignition ON, verify that a test lamp does not illuminate between Q38 Throttle Body Motor Control Circuit terminal 3 (X1) and B+.

⇒	If test lamp illuminates, test the Q38 Throttle Body Motor Control Circuit terminal 3 (X1) for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

6. Ignition ON, verify that a test lamp does not illuminate between motor control circuit terminal 5 (X1) and B+.

⇒	If test lamp illuminates, test the Q38 Throttle Body Motor Control Circuit terminal 5 (X1) for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

7. Ignition OFF, allow sufficient time for the ECM to completely power down. Connect a DMM between the Q38 Throttle Body Motor Control Circuit terminal 5 (X1) and ground.

Note: When measuring peak voltage, ensure that the DMM is on the proper voltage scale that the response time is set to 1 ms.

8. Measure for B+ on the Q38 Throttle Body Motor Control Circuit terminal 3 (X1) as the ignition is turned ON.

⇒	If the peak voltage is not within 1 V of B+, test for an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

9. Ignition OFF, allow sufficient time for the ECM to completely power down. Connect a DMM between the motor control terminal 5 (X1) circuit and ground.
10. Measure for B+ on the Q38 Throttle Body Motor Control Circuit terminal 5 (X1) as the ignition is turned ON.

⇒	If the peak voltage is not within 1 V of B+, test for an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

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

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.