Circuit Description
The malfunction indicator lamp (MIL) is located on the instrument panel cluster. The MIL will illuminate when there is an emission related failure or the ignition is ON with the engine OFF. Ignition 1 voltage is supplied to the MIL. The engine control module (ECM) turns the MIL ON by grounding the control circuit of the MIL using a low side driver. The ECM monitors the voltage level on the control circuit of the MIL. If the ECM detects a short to voltage on the control circuit of the MIL, this DTC sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1660 Malfunction Indicator Lamp (MIL) Control Circuit High Voltage
Conditions for Running the DTC
| • | The ignition is ON or the engine is operating. |
| • | The ignition 1 voltage is more than 10 volts. |
| • | DTC P1660 runs continuously once the above conditions are met. |
Conditions for Setting the DTC
The ECM detects a short to voltage on the control circuit of the MIL.
Action Taken When the DTC Sets
| • | The MIL will illuminate. |
| • | The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records. |
| • | A history DTC is stored. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after 4 consecutive ignition cycles in which the diagnostic runs without a fault. |
| • | A history DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | DTCs can be cleared by using the scan tool. |
| • | Disconnect the ECM battery feed for more than 10 seconds. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connect End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | |
2 |
Does DTC P1660 set? | -- | Go to Step 4 | Go to Step 3 |
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Intermittent Conditions |
Does the MIL illuminate? | -- | Go to Step 5 | Go to Step 6 | |
5 | Test for shorted terminals and poor connections at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 7 |
6 | Repair a short to voltage on the control circuit of the MIL. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 8 | -- |
7 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 8 | -- |
8 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 9 |
9 | Are there any DTCs that have not been diagnosed? | -- | System OK | |
