GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • 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

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Ignition 1 Voltage-Powertrain Relay

P0689

P0689, P1682

P0690

--

Ignition 1 Voltage-Ignition Main Relay

--

P1682

--

--

Typical Scan Tool Data

Ignition Scan Tool Data

Circuit

Short to Ground

Open

Short to Voltage

Operating Conditions: Ignition ON, engine OFF, and ignition main and powertrain relay are commanded ON

Ignition 1 Voltage, Ignition Main

0 Volts

0 Volts

12 Volts

EC Ignition (Powertrain) Relay Feedback Signal

0 Volts

0 Volts

12 Volts

Circuit/System Description

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 ignition main 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.

Conditions for Running the DTC

    • The ignition is ON.
    • System voltage is more than 5.23 volts.
    • The powertrain relay is commanded ON.
    • DTC P1682 runs continuously.

Conditions for Setting the DTC

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.

Action Taken When the DTC Sets

DTC P1682 is a Type A code.

Conditions for Clearing the DTC

DTC P1682 is a Type A code.

Diagnostic Aids

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

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Engine Control Module Connector End Views
    •  Engine Controls Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions
    •  Scan Tool Output Controls

Special Tools Required

J 35616 Connector Test Adapter Kit

Circuit/System Verification

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

  1. If DTCs P0685, P0689, or P0690 are set, diagnose those DTCs first.
  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.
  3. 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.

Circuit/System Testing

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

Testing the Ignition 1 Signal Circuit

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

  1. Ignition ON, verify that B+ is available to both test points of the inline fuse from the ignition main relay to the ECM.
  2. If B+ is only available on one test point of the fuse, test the ignition 1 voltage circuit from the fuse to the ECM for a short to ground. If the circuit tests normal, replace the ECM.
    If B+ is not available on either test point of the fuse, replace the underhood fuse block.
  3. Ignition OFF, disconnect the ECM C1 connector.
  4. Ignition ON, verify that B+ is available at C1-19.
  5. If B+ is not available, test the ignition 1 voltage circuit for an open/high resistance condition. If the circuit tests normal, replace the ECM.
  6. If all circuits test normal, replace the ECM.

Testing the EC Ignition Relay Feedback Circuit

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

  1. Ignition OFF, remove the powertrain relay from the underhood fuse block.
  2. Ignition ON, connect a 3A fused jumper wire from B+ to the powertrain ignition 1 voltage circuit terminal. Verify that the EC Ignition Relay Feedback parameter displays B+ on the scan tool.
  3. If the scan tool parameter is less than the specified value, test the ignition 1 voltage circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the ECM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Control Module References for ECM replacement, programming, and setup
    •  Relay Replacement
    •  Accessory Wiring Junction Block Replacement