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, P1516, P1682 | P0689, P1516, P1682, P2101 | P0690 | --
Ignition 1 Voltage (Run/Crank Relay) | -- | ¹ | P0575, P0650 | --
¹The condition causes no start condition.

### Typical Scan Tool Data

#### Engine Control Ignition Relay Feedback

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: Ignition ON, Engine OFF. Powertrain relay is commanded ON
Ignition 1 Voltage | 0 V | 0 V | 12 V

#### 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 V | 0 V | 12 V

### 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, through a fuse. 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. The ignition 1 voltage provides power to other internal ECM circuits, except those associated with TAC operation. The ECM continuously monitors the voltage difference between the 2 circuits.

### Conditions for Running the DTC

• | The ignition switch is in Unlock/Accessory, Run or Crank.

• | System voltage is greater 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 difference between the ignition 1 voltage of the Run/Crank relay and the ignition 1 voltage of the powertrain is more than 3 volts.

• | It occurs every time in 14 times tests.

### Action Taken When the DTC Sets

• | DTC P1682 is a Type A DTC.

• | The 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

• | Power Distribution Schematics

#### Connector End View Reference

• | Engine Control Module Replacement

• | 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

• | Probing Electrical Connectors

• | Electrical Center Identification Views

#### DTC Type Reference

Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Scan Tool Data List

### Circuit/System Verification

1. If DTC P0685, P0690, or P1380 are set, diagnose those DTCs first.
2. With the engine OFF, turn the ignition ON, observe the Ignition 1 signal, and the EC Ignition Relay Feedback Signal parameters on the scan tool. Display no more than 3 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 volt, before the ECM powers down.

### Circuit/System Testing

1. Ignition ON, observe the Ignition 1 Signal and EC Ignition Relay Feedback Signal parameters on the scan tool to determine which is less than B+.
2. Ignition OFF, remove the relay that corresponds to the scan tool parameter that is less than battery positive.

Note: Six ohms or greater in the circuit/underhood fuse block will cause the DTC to set.

3. Ignition On, connect a 3-amp fused jumper wire between battery positive voltage and the appropriate ignition 1 circuit terminal.

⇒ | If the appropriate scan tool parameter is less than the specified value, test the ignition 1 circuit for an open/high resistance. If the circuit test normal, replace the ECM. If the circuit test 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.

Control Module References for ECM replacement, setup, and programming