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) | P1682, P2176 | P1516, P1682, P2101 | -- | --
Ignition 1 Voltage (Ignition Main 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. Ignition Main 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 powertrain control module (PCM). 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 PCM circuits associated with the throttle actuator control (TAC) operation. The ignition main relay provides the second ignition 1 voltage circuit to the PCM through a fuse. This ignition 1 voltage provides power to other internal PCM circuits, except those associated with TAC operation. The PCM 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.

• | The system voltage is more than 5.23 volts.

• | The 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 ignition main 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

Engine Controls Connector End Views

#### Description and Operation

Powertrain 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

• | Scan Tool Data List

• | Scan Tool Output Controls

### Circuit/System Verification

1. 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 2 parameters.
2. Ignition OFF, observe the ignition 1 voltage signal parameter on the scan tool. The parameter value should be 0 volts before the PCM powers down.

### 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 powertrain relay to the PCM.

⇒ | If B+ is only available on one test point of the fuse, test the ignition 1 voltage circuit from the fuse to the PCM for a short to ground. If the circuit tests normal, replace the PCM.

⇒ | If B+ is not available on either test point of the fuse, replace the underhood fuse block.

2. Ignition OFF, disconnect the PCM C1 connector.
3. Ignition ON, verify that B+ is available at C1-19.

⇒ | If B+ is not available, test the ignition 1 voltage circuit for an open/high resistance conditions. If the circuit tests normal, replace the PCM.

4. If all circuits test normal, replace the PCM.

#### 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 from the underhood fuse block.
2. Ignition ON, connect a 3A fused jumper wire from B+ to the powertrain ignition 1 voltage circuit terminal. Verify that the EC Ignition Relay Feedback parameter displays B+ on the scan tool.

⇒ | 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 PCM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Relay Replacement

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