P1682

DTC P1682

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P1682
- Ignition 1 Switch Circuit 2

Diagnostic Fault Information






Typical Scan Tool Data










Circuit/System Description

There are 2 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 printed circuit board 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.

Conditions for Running the DTC

* The ignition is in the Unlock/Accessory, Run, or Crank position.
* System voltage is more than 5.23 volts.
* Powertrain relay is commanded ON.
* DTC P1682 runs continuously when the above conditions are met.

Conditions for Setting the DTC

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

Action Taken When the DTC Sets

DTC P1682 is a Type B DTC.

Engine may operate in a reduced engine power mode.

Conditions for Clearing the DTC

DTC P1682 is a Type B DTC.

Circuit/System Verification

1. If DTCs P0685, P0690, or B1380 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.

Circuit/System Testing

1. Ignition ON, observe the Ignition 1 Signal and EC Ignition Relay Feedback scan tool parameters 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: Six ohms or greater in the circuit/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, test or replace the applicable relay/underhood fuse block.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

* Control Module References for ECM replacement, setup, and programming Programming and Relearning
* Relay Replacement (Within an Electrical Center) Relay Replacement (Attached to Wire Harness) Verification Tests