There are two ignition 1 voltage circuits supplied to the engine control module (ECM). The first ignition 1 voltage circuit is provided by the powertrain relay through a fuse. This ignition 1 voltage circuit supplies power to all the internal ECM circuits associated with the throttle actuator control (TAC) operation. The ignition main relay provides the second ignition 1 voltage circuit to the ECM through a fuse. This ignition 1 voltage provides power to other internal ECM circuits, except those associated with TAC operation. The ECM continuously monitors the voltage level difference between the 2 circuits.

The ignition 1 voltage of the ignition main relay is more than 3 volts different than the ignition 1 voltage of the powertrain relay for more than 2 seconds.

DTC P1682 is a Type A DTC.

Schematic Reference

Connector End View Reference

Component Connector End Views

Description and Operation

Engine Control Module Description

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. If DTCs P0685, P0689, or P0690 are set, diagnose those DTCs first.
2. Ignition ON, engine OFF, observe the Ignition 1 voltage signal and the EC Ignition Relay Feedback signal parameters on the scan tool. Both parameter values should display no more than 3 volts difference between the 2 parameters.
3. Ignition OFF, observe the ignition 1 voltage signal parameter on the scan tool. The parameter value should be 0 volts before the ECM powers down.

1. Ignition OFF, disconnect the powertrain relay.
2. Ignition ON, verify that a test lamp does not illuminate between the powertrain relay controlled output circuit terminal and ground.

⇒	If the test lamp illuminates, test the powertrain relay controlled output circuit for a short to voltage.

3. Ignition OFF, verify that a test lamp illuminates between the powertrain relay coil voltage supply circuit terminal and ground.

⇒	If the test lamp does not illuminate, test the powertrain relay coil voltage supply circuit for a short to ground or an open/high resistance.

4. Verify that a test lamp illuminates between the powertrain relay switch voltage supply circuit terminal and ground.

⇒	If the test lamp does not illuminate, test the powertrain relay switch voltage supply circuit for an open/high resistance.

5. Disconnect the ECM.
6. Ignition ON, verify that a test lamp illuminates between ECM connector terminal 19 X1 and ground.

⇒	If the test lamp does not illuminate, test the ignition 1 relay controlled output circuit for a short to ground or open/high resistance. If the circuit tests normal and its fuse is open, replace the ECM.

7. Ignition OFF, connect the harness connector at the ECM.
8. Ignition ON, connect a jumper wire between the powertrain relay voltage supply circuit terminal and the powertrain relay controlled output circuit terminal. Verify the EC Ignition Relay Feedback parameter indicates battery positive voltage.

⇒	If not the specified value, test the powertrain relay controlled output circuit for a short to ground or an open/high resistance. If the circuit tests normal and its fuse is open, replace the ECM.

9. If all circuits test normal, replace the powertrain relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.