There are 2 ignition 1 voltage circuits supplied to the engine control module (ECM). The first ignition 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 second ignition 1 voltage circuit is supplied by the run crank relay through a fuse, and is used to power the remaining internal ECM circuits. If the ECM detects a voltage difference between the 2 ignition 1 voltage circuits, DTC P1682 will set.

The ECM detects that the voltage level difference is greater than 3 volts between the 2 ignition 1 voltage circuits for less than 1 second.

DTC P1682 is a Type A DTC.

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

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Special Tools Required

J 35616 Connector Test Adapter Kit

1. If DTCs P0685, P0689, or P0690 are set, diagnose those DTCs first.

Important: On the scan tool, the powertrain relay is referred to as the ignition relay.

2. Ignition ON, engine OFF, observe both 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.

⇒	If the vehicle passes the Circuit/System Verification test, operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records data list.

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

1. Ignition ON, observe the Ignition 1 Signal and the EC Ignition Relay Feedback scan tool parameter to determine which is less than B+.
2. Ignition OFF, remove the relay that corresponds to the scan tool parameter that is less than B+.

Important: A resistance of 5 ohms or greater in the circuit or underhood fuse block will cause the DTC to set.

3. Ignition ON, connect a 3A fused jumper wire between B+ and the applicable ignition 1 circuit terminal. Verify that the applicable scan tool parameter displays B+.

⇒	If the applicable scan tool parameter is less than the specified value, test the ignition 1 circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

4. If all circuits test normal, replace the applicable relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.