Circuit Description
Ignition voltage is supplied directly to the malfunction indicator lamp (MIL). The powertrain control module (PCM) controls the lamp by grounding the control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the PCM. When the PCM is commanding a component ON, the voltage of the control circuit should be near 0 volts. When the PCM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be near battery voltage. If the fault detection circuit senses a voltage other than what is expected, this diagnostic trouble code (DTC) will set.
Conditions for Running the DTC
| • | The ignition voltage is between 9-18 volts. |
| • | The engine speed is more than 80 RPM. |
| • | The PCM driver transitions from ON to OFF or from OFF to ON. |
Conditions for Setting the DTC
| • | A short to ground, an open circuit, or a short to battery voltage is detected on the control circuit. |
| • | The condition is present for at least 30 seconds. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the 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. |
Diagnostic Aids
Notice: Use the connector test adapter kit J 35616-A for any test that
requires probing the following items:
• The PCM harness connectors • The electrical center fuse/relay cavities • The component terminals • The component harness connector
Important: The MIL is actually a light emitting diode (LED). An LED requires a parallel dropping resistor in order to operate on a 12-volt system. If the LED burns out, the dropping resistor will still pass voltage on to the PCM, and the MIL diagnostic trouble code (DTC) may not set even though the MIL is inoperative. If the power supply circuit to the indicator lamps and the MIL control circuit check out OK, the instrument panel (IP) cluster needs to be checked for a faulty LED. Refer to Diagnostic System Check - Instrument Cluster in Instrument Panel, Gauges and Console.
If the problem is intermittent, refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Normally, ignition feed voltage should be present on the control circuit with the PCM disconnected and the ignition turned ON.
-
This step checks for a shorted component or a short to B+ on the control circuit. Either condition would result in a measured current of over 500 milliamperes. This step also checks for a component that is causing an open circuit while being operated, resulting in a measured current of 0 milliamperes.
-
This step checks for a short to voltage on the control circuit.
-
This vehicle is equipped with a PCM which utilizes an electrically erasable programmable read only memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
2 | Turn the MIL ON and OFF with the scan tool. Does the MIL turn ON and OFF? | -- | Go to Diagnostic Aids | Go to Step 3 |
Is voltage near the specified value? | B+ | Go to Step 4 | Go to Step 7 | |
Does the current reading remain between the specified values? | 5-50 mA | Go to Step 12 | Go to Step 5 | |
Is voltage at the specified value? | 0 V | Go to Step 11 | Go to Step 6 | |
6 | Locate and repair the short to voltage in the MIL control circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 16 | -- |
7 | Check the ignition feed fuse for the instrument panel indicators. Is the fuse blown? | -- | Go to Step 8 | Go to Step 9 |
8 |
Is the action complete? | -- | Go to Step 16 | -- |
9 |
Is the voltage near the specified value? | B+ | Go to Step 10 | Go to Step 14 |
10 |
Was a problem found and corrected? | -- | Go to Step 16 | Go to Step 11 |
11 |
Was a problem found and corrected? | -- | Go to Step 16 | Go to Diagnostic System Check - Instrument Cluster in Instrument Panel, Gauges and Console |
12 |
Does the test lamp turn ON and OFF? | -- | Go to Diagnostic Aids | Go to Step 13 |
13 |
Was a problem found and corrected? | -- | Go to Step 16 | Go to Step 15 |
14 | Locate and repair the open in the ignition feed circuit to the IP indicators. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 16 | -- |
Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 16 | -- | |
16 |
Does the DTC run and pass? | -- | Go to Step 17 | Go to Step 2 |
17 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
