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)

P1516, P1682, P2176

B1325, P0575, P1682, P2101

P0690, P2070

--

Ignition 1 Voltage (Run/Crank Relay)

--

--

P0575, P0650

--

Typical Scan Tool Data

EC Ignition Relay Feedback

Circuit

Short to Ground

Open

Short to Voltage

Operating Conditions: Ignition ON engine OFF. Powertrain relay commanded ON.

Ignition 1 Voltage

0 Volts

0 Volts

12 Volts

Ignition 1 Signal

Circuit

Short to Ground

Open

Short to Voltage

Operating Conditions: Ignition ON engine OFF. Run/Crank relay commanded ON.

Ignition 1 Voltage

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 1 voltage circuit is provided by the powertrain relay, which is PWR/TRN relay 33, 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 run/crank 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 run/crank relay is more than 2 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 A DTC.
    • Engine may operate in a reduced engine power mode.

Conditions for Clearing the DTC

DTC P1682 is a Type A DTC.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Engine Control Module Description

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

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 2 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

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 fuse from the run/crank relay, which is PWR/TRN relay 33, 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 X1 connector.
  4. Ignition ON, verify that B+ is available at X1-19.
  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, which is PWR/TRN relay 33, from the underhood fuse block.
  2. Ignition ON, connect a 3A fused jumper wire from B+ to the powertrain relay ignition 1 voltage circuit terminal 4. 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.

    •  Relay Replacement
    •  Control Module References for ECM replacement, setup, and programming