Circuit Description
The engine control module (ECM) contains data, which is essential for proper throttle actuator control (TAC) system operation. The ECM continuously checks the integrity of this data. If the ECM detects a fault in the TAC system, the ECM disables the TAC motor. The accelerator pedal position (APP) sensor will have no affect on the throttle position (TP) and the throttle will remain in the default position. If the ECM detects an internal fault or any fault that causes the throttle to be at the default position and the engine does not respond within the predetermined limits, DTC P2108 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P2108 Throttle Actuator Control (TAC) Module Performance
Conditions for Running the DTC
| • | The ignition is ON. |
| • | DTC P2108 runs continuously once the above condition is met. |
Conditions for Setting the DTC
The difference between the calculated and the actual throttle position is more than a predetermined value.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records. |
| • | The control module 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
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
| • | Inspect for a condition in which the throttle valves may have been held open. |
| • | Inspect for conditions in which ice may have formed in the throttle bore. |
| • | The throttle valves are spring loaded to a slightly open position. |
| • | The throttle valves should not be completely closed, nor should they be open any more than the specified amount. |
| • | The throttle valves should move to the open and closed position without binding under the normal spring pressure. |
| • | The throttle should NOT be free to move open or closed WITHOUT spring pressure. |
| • | The scan tool has the ability to operate Throttle Control System using the Throttle Position function located in the TAC System menu. This function will operate the throttle valve through the entire range in order to determine if the throttle body and system operate correctly. |
| • | If the condition is intermittent, refer to Intermittent Conditions . |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 | Are any other DTCs set? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 3 |
3 | Replace the engine control module (ECM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 4 | -- |
4 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 5 |
5 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK |
