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 of the 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, P1682, P2176

P0689, P1516, P1682, P2101

P0690

--

Ignition 1 Voltage (Run/Crank Relay)

--

P1682

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 two 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 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 two 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 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 A DTC.

Engine may operate in a reduced engine power mode.

Conditions for Clearing the DTC

DTC P1682 is a Type A DTC.

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

Component Connector End Views

Description and Operation

Engine Control Module Description

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

Control Module References for scan tool information

Circuit/System Verification

  1. If DTCs P0685, P0689, 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 two 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 OFF, disconnect the Powertrain Relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the powertrain relay controlled output circuit terminal and ground.
  3. If the test lamp illuminates, test the powertrain relay controlled output circuit for a short to voltage.
  4. Ignition OFF, verify that a test lamp illuminates between the powertrain relay coil voltage supply circuit terminal and ground.
  5. If the test lamp does not illuminate, test the powertrain relay coil voltage supply circuit for a short to ground or an open/high resistance.
  6. Verify that a test lamp illuminates between the powertrain relay switch voltage supply circuit terminal and ground.
  7. If the test lamp does not illuminate, test the powertrain relay switch voltage supply circuit for an open/high resistance.
  8. Disconnect the ECM.
  9. Ignition ON, verify that a test lamp illuminates between ECM connector terminal 19 X1 and ground.
  10. If the test lamp does not illuminate, test the RUN/CRNK Relay controlled output circuit for a short to ground or open/high resistance. If the circuit tests normal and its fuse is open, replace the ECM.
  11. Ignition OFF, connect the harness connector at the ECM.
  12. Ignition ON, connect a 3A fused jumper wire between the powertrain relay voltage supply circuit terminal and the powertrain relay controlled output circuit terminal. Verify the EC Ignition Relay Feedback parameter indicates battery positive voltage.
  13. If not the specified value, test the powertrain relay controlled output circuit for a short to ground or an open/high resistance. If the circuit tests normal and its fuse is open, replace the ECM.
  14. If all circuits test normal, replace the Powertrain Relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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