For 1990-2009 cars
Engine Controls Components
Cell 20: MIL and DLC
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The test switch terminal is located in the duty check data link connector behind the glovebox. The PCM sets the ignition timing to the base setting when the test switch terminal is grounded.

### Condition for Running the DTC

• | The engine is running at a steady speed.

• | The engine operating in Close Loop.

### Conditions for Setting the DTC

• | The vehicle speed is above 2 km/h (1 mph).

• | The test switch is ON.

• | The condition is present for 5 seconds

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL).

• | The PCM records the operating conditions at the time that the diagnostic fails. The Freeze Frame buffer stores this information.

### Conditions for Clearing the MIL/DTC

• | The PCM turns OFF the MIL after three consecutive trips, during which the diagnostic runs and a fault is not detected.

• | A History DTC clears after 40 consecutive warm-up cycles without a fault.

• | Use the Clear DTC Information function on the scan tool in order to clear the DTC information.

### Diagnostic Aids

Check for a damaged wiring harness. Inspect the wiring harness for damage that may cause a short to ground. With the engine running, wiggle the wiring harness to the duty check data link connector. Use the scan tool in order to read the test switch status for the Spark Advance Adjust parameter. An ON display on the scan tool indicates that the harness is shorting to ground.

### Test Description

The numbers below refer to the step numbers in the diagnostic table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks, and to save the applicable Freeze Frame data on the scan tool. This creates an electronic copy of the data that was taken when the fault occurred. The scan tool saves the information for later reference.

2. This step determines if a fault is present.

3. This step checks for a short to ground on the test switch terminal and on the circuitry. If there is a short to ground in the test switch signal circuit, the ignition timing will be held at the base timing.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Install a scan tool.
2. Perform the clear DTC information function on the scan tool.
3. Start the engine.
4. Use the scan tool to read the test switch status for the Spark Advance Adjust

Does the scan tool indicate the Spark Advance Adjust parameter is ON?

--

Go to Step 3

Go to Diagnostic Aids

3 |

1. Turn ON the ignition, leaving the engine OFF.
2. Measure the voltage from the test switch signal circuit, terminal 5 of the duty check data link connector, to ground with a DMM.

Is the voltage near the specified value?

5 V

Go to Diagnostic Aids

Go to Step 4

4 |

1. Check the test switch signal circuit for a short to ground.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 6

Go to Step 5

5 | Replace the PCM. Is the action complete? | -- | Go to Step 6 | --
6 |

1. Perform the Clear DTC Information function on the scan tool, and road-test the vehicle within the Freeze Frame conditions which set the DTC.
2. Review the scan tool data, and check the data for DTCs. The repair is complete if no DTCs are displayed.

Does the scan tool display any DTCs?

--

Go to the applicable DTC table

System OK