There are 2 ignition 1 voltage circuits supplied to the engine control module (ECM). The first ignition 1 voltage circuit is provided by the PWR/TRN 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 IGN 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 Run/Crank relay is more than 3 volts different than the ignition 1 voltage of the powertrain relay for more than 1 second.

DTC P1682 is a Type A DTC.

This test procedure requires that the vehicle battery has passed a load test and is completely charged. Refer to Battery Inspection/Test.

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, P0690, or B1370 are set, diagnose those DTCs first.
2. Ignition ON, engine OFF, observe the Ignition 1 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.
4. Engine running, observe the DTC information with a scan tool. DTC P1682 should not set.
5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

1. Ignition OFF, disconnect the powertrain relay using the J 43244 Pliers .
2. Ignition ON, verify that a test lamp does not illuminate between the ignition circuit terminal 87 and ground.

⇒	If the test lamp illuminates, test the ignition circuit for a short to voltage.

3. Ignition OFF, verify that a test lamp illuminates between the B+ circuit terminal 85 and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

4. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.

5. Disconnect the X2 harness connector at the ECM.
6. Test for less than 2 ohms between ground and the ECM terminal 73 X2.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

7. Ignition ON, verify that a test lamp illuminates between connector terminal 19 X1 and ground.

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

8. Ignition OFF, connect the harness connector at the ECM.
9. Ignition ON, connect a jumper wire between the B+ circuit terminal 30 and the ignition circuit terminal 87. Verify that the EC Ignition Relay Feedback Signal parameter indicates B+ voltage.

⇒	If the parameter does not indicate B+ voltage, test the ignition circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

10. Ignition OFF, allow the ECM to completely power down.
11. Verify that a test lamp does not illuminate between the B+ circuit terminal 85 and the control circuit terminal 86.

⇒	If the test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.

12. Remove the test lamp.
13. Ignition ON, verify the scan tool EC Relay Ckt. Short Volts Test Status parameter is OK.

⇒	If not the specified value, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.

14. Install a 3A fused jumper wire between the control circuit terminal 86 and the B+ circuit terminal 85. Verify the scan tool EC Relay Ckt. Short Volts Test Status parameter is Fault.

⇒	If not the specified value, test the control circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming