For 1990-2009 cars

### 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, P1682, P2176 | P0689, P1516, P1682 | P0689 | --
Ignition 1 Voltage (Run/Crank Relay) | -- | P1682 | P0650 | --

### 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 Ignition Relay or the Main 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 On or the engine is running.

• | The system voltage is greater than 5 volts.

• | The ignition relay or the main relay is commanded ON.

• | DTC P1682 runs continuously once the above conditions are met.

### Conditions for Setting the DTC

The ignition 1 voltage of the Run/Crank relay is greater than 3 volts different than the ignition 1 voltage of the main relay for greater than 2 seconds.

### Action Taken When the DTC Sets

DTC P1682 is a Type B DTC.

### Conditions for Clearing the DTC

DTC P1682 is a Type B 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 .

• | The engine may operate in a reduced engine power mode.

### Reference Information

#### Schematic Reference

• | Engine Controls Schematics

• | Power Distribution 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. Ignition ON, observe the DTC information with a scan tool. DTC P1682 should not set.
2. Ignition ON, observe the scan tool Ignition 1 voltage parameter and the scan tool EC Ignition Relay Feedback parameter. Both readings should be less than 3 volts difference between the two parameters.
3. Ignition OFF, observe the scan tool ignition 1 voltage parameter. The reading should be 0 volts, before the ECM powers down.

### Circuit/System Testing

1. Ignition ON, observe the scan tool Ignition 1 Signal parameter and the scan tool EC Ignition Relay 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: 6 ohms or greater in the circuit/underhood fuseblock 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 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.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Relay Replacement

• | Control Module References for ECM replacement, setup, and programming