Malfunction Indicator Lamp (MIL) Diagnosis
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Malfunction Indicator Lamp (MIL) Diagnosis
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Circuit/System Description
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The malfunction indicator lamp (MIL) also known as the service engine soon (SES) or check engine lamp, is located on the instrument cluster. The MIL, when illuminated, informs the driver of an emission system fault, and that service to the system is required. An ignition circuit supplies power to the lamp and the engine control module (ECM) provides a switched ground.
Schematic Reference
Connector End View Reference
Component Connector End Views
Electrical Information Reference
Scan Tool Reference
Control Module References
for scan tool information
Circuit/System Verification
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Note
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Any MIL requesting DTCs that may be set should be diagnosed first.
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Ignition ON, the MIL should turn ON and OFF when commanded with a scan tool.
1.
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Ignition OFF, disconnect the harness connector at the P16 instrument cluster.
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2.
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Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 19 X1 and ground.
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3.
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If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, replace the P16 instrument cluster.
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4.
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Connect a test lamp between the control circuit terminal 17-X1 and the ignition circuit terminal 19-X1.
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5.
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Command the MIL ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
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6.
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If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the K20 ECM.
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7.
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If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
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8.
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If all circuits test normal, replace the P16 instrument cluster.
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Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
Control Module References
for ECM and instrument cluster replacement, setup, and programming