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 | P0689, P1682 | P0690 | --
Ignition 1 Voltage, Run/Crank Relay | -- | P1682 | -- | --

### Typical Scan Tool Data

#### Ignition 1 Signal

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: Ignition ON, engine OFF, and run/crank and powertrain relay are commanded ON
Ignition 1 Voltage, Run/Crank | 0 Volts | 0 Volts | B+
EC Ignition (Powertrain) Relay Feedback Signal | 0 Volts | 0 Volts | B+

### Circuit/System Description

There are 2 ignition voltage circuits supplied to the engine control module (ECM). The first ignition circuit is provided by the engine controls ignition relay or main relay, through a fuse. This ignition voltage circuit supplies power to all the internal ECM circuits associated with the throttle actuator control (TAC) operation. The second ignition voltage circuit is supplied by the run/crank 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 voltage circuits, DTC P1682 will set.

### Conditions for Running the DTC

• | The ignition is ON.

• | System voltage is more than 6 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 voltage circuits for less than 1 second.

### Action Taken When the DTC Sets

DTC P1682 is a Type A DTC.

### 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

#### 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. Verify DTCs P0685, P0689, or P0690 are set.

⇒ | If any of the above DTCs are set, refer to DTC P0685, P0689, or P0690 for further diagnosis.

2. Ignition ON, observe the scan tool EC Ignition Relay Feedback signal parameter. The parameter should display B+.

⇒ | If less than the specified value, refer to DTC P0685, P0689, or P0690 for further diagnosis.

3. Ignition ON, observe the scan tool Control Module Voltage signal and the EC Ignition Relay Feedback signal parameters. Both parameters should display within 3 V.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

1. Ignition OFF, disconnect the ECM harness connector X1.
2. Ignition ON, load test for B+ between the ECM harness connector terminals listed below and ground.

• | X1-12

• | X1-14

⇒ | If less than the specified value, repair the appropriate ignition voltage circuits for a short to ground or an open/high resistance.

3. If all circuits test normal, replace the ECM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming