The engine control module (ECM) main relay is energized when the ECM receives an ignition switch ON signal.

The ECM detects that the ECM main relay has been ON, high voltage, after the ignition switch was turned OFF.

DTC P0687 is a Type D DTC.

DTC P0687 is a Type D DTC.

Inspect for any recent engine mechanical repairs. An incorrectly installed ECM main relay will cause this DTC to set.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Verify the integrity of the ECM Main Relay by inspecting for the following conditions:

Important: You must perform Circuit/System Verification before proceeding with Circuit/System Testing.

1. Ignition OFF and the ECM main relay harness disconnected, measure for 0 volts on the ECM main relay circuits.

⇒	If the voltage is more than 0 volts, test the affected motor control circuit for a short to voltage.

⇒	If the circuits test normal, replace the ECM main relay.

2. Ignition OFF and the ECM main relay harness disconnected, probe the ECM main relay circuits with a test lamp connected to battery voltage. Verify the test lamp does illuminate on either circuit.

⇒	If the test lamp does not illuminate, test the affected motor control circuit for a short to ground. If the circuits test normal, replace the ECM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for engine control module (ECM) replacement, setup, and programming