Circuit Description
The throttle actuator control (TAC) motor is controlled by the TAC module using various inputs from the powertrain control module (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. In order to increase idle speed, the TAC module commands the throttle plate open, allowing more air to pass the throttle plate. If the actual idle RPM does not match the desired idle RPM within a calibrated time, DTC P0506 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0506 Idle Speed Low
Conditions for Running the DTC
| • | DTCs P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125, P0128, P0171, P0172, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0300, P0401, P0404, P0405, P0443, P0496, P0502, P0503, P1106, P1107, P1111, P1112, P1114, P1115, P1125, P1404, P1516, P2101, P2107, P2108, P2119, P2120, P2125, P2135, P2138 are not set. |
| • | DTCs P2A01, P0401, P0420 have passed. |
| • | The engine is operating. |
| • | The engine coolant temperature (ECT) is more than -40°C (-40°F). |
| • | The intake air temperature (IAT) is more than -40°C (-40°F). |
| • | The barometric pressure (BARO) is more than 60 kPa. |
| • | The system voltage is between 11-18 volts. |
| • | The vehicle speed is less than 4.8 km/h (3 mph). |
| • | The throttle position angle is less than 0.25 percent. |
Conditions for Setting the DTC
| • | The difference between the actual idle RPM and the desired idle RPM exceeds a calibrated limit. This limit varies from 300 RPM at -40°C (-40°F) to 100 RPM at 152°C (305°F) based on ECT. |
| • | The above condition is present for 8 seconds in order for the test to fail. Four tests must fail in order to set this DTC. The vehicle must exit conditions for running between each test. |
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/Failure Records. |
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. |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views and Engine Controls Connector End Views | |||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |||||||||
Does the engine speed correspond within 100 RPM with each command? | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 | |||||||||
3 | Inspect for any condition that can reduce idle speed by increasing engine load. The following examples are possible conditions:
Did you complete the action? | Go to Step 4 | -- | ||||||||
4 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 5 | ||||||||
5 |
Important: Be aware that repairing one individual condition may correct more than one DTC. Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | System OK | |||||||||
