Circuit Description
The throttle actuator motor is controlled by the TAC module using various inputs from the PCM which are communicated across serial data. The DC motor located on the throttle body drives the throttle plate. In order to decrease idle speed, the TAC module commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the TAC module commands the throttle plate open allowing more air to bypass the throttle plate. If the Actual idle RPM does not match the Desired idle RPM within a calibrated time, this DTC sets.
Conditions for Running the DTC
| • | No Misfire, EGR, TP, VSS, ECT, MAP, IAT, Fuel trim, Fuel injector, CKP or MAF DTCs set. |
| • | Engine is operating for at least 2 minutes. |
| • | ECT is more than -40°C (-40°F) |
| • | IAT is more than -40°C (-40°F) |
| • | BARO is more than 65 kPa |
| • | System voltage is between 9.0 and 18.0 volts |
| • | Vehicle speed is less than 3 mph |
| • | APP indicated angle is less than 0.25 percent |
Conditions for Setting the DTC
| • | The Actual idle speed is approximately 175 RPM higher than the Desired idle speed. |
| • | All above conditions present for 15 seconds. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) during the first trip in which the diagnostic test has been run and failed. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has run and passed. |
| • | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using a scan tool. |
Diagnostic Aids
Inspect for the following:
Many situations may lead to an intermittent condition. Perform each inspection or test as directed.
Important: : Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.
| • | Loose terminal connection |
| - | Use a corresponding mating terminal to test for proper tension. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair. |
| - | Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair. |
| • | Damaged harness--Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair. |
| • | Inspect the powertrain control module (PCM) and the engine grounds for clean and secure connections. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair. |
If the condition is determined to be intermittent, reviewing the Snapshot or Freeze Frame/Failure Records may be useful in determining when the DTC or condition was identified.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||
Does the engine speed correspond, within 100 RPM, with each command? | -- | Go to Diagnostic Aids | ||||||
3 | Is the engine RPM more than 100 RPM more than or less than Desired RPM? | -- | ||||||
4 | Inspect for the following conditions:
Did you complete the repair? | -- | -- | |||||
5 | Inspect for the following conditions:
Did you complete the repair? | -- | -- | |||||
6 |
Does the DTC reset? | -- | ||||||
7 | Does the scan tool indicated any DTCs set that you have not diagnosed? | -- | Go to applicable DTC table | System OK |
