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 C0450 01: Steering Assist Control Actuator Circuit Short to Battery
DTC C0450 02: Steering Assist Control Actuator Circuit Short to Ground
DTC C0450 04: Steering Assist Control Actuator Circuit Open

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Variable Effort Steering Actuator Control Circuit 1 | C0450 02 | C0450 04 | C0450 01 | --
Variable Effort Steering Actuator Control Circuit 2 | C0450 02 | C0450 04 | C0450 01 | --

### Circuit/System Description

The actuator is a variable electromagnetic actuator, which consists of one multiple-pole ring-style permanent magnet, with a pole piece, and an electromagnetic coil assembly. By commanding currents between -3 to +3 A through the coils the steering effort will be adapted accordingly.

### Conditions for Running the DTC

• | System voltage between 9-16 V

• | Engine RUN

### Conditions for Setting the DTC

The variable effort steering detects a short to battery, short to ground or an open circuit in the actuator circuits.

#### C0450 01

If the coil feedback voltage is measured greater than 8 V during the initialization of the controller, the DTC will be set.

#### C0450 02

If the coil feedback voltage is measured less than 3.4 V during the initialization of the controller, the DTC will be set.

#### C0450 04

If the coil current is measured less/greater than 1.0 A , the DTC will be set.

### Action Taken When the DTC Sets

• | DTC C0450 is stored in memory.

• | Fault lamp illuminates.

• | The variable effort steering module goes in to shutdown mode.

### Conditions for Clearing the DTC

• | The condition for setting the DTC is no longer present and the DTC is cleared with a scan tool.

• | The variable effort steering automatically clears the history DTC when a current DTC is not detected in 40 consecutive drive cycles.

### Diagnostic Aids

The vehicle may need to be driven to view full variable effort steering actuator commanded and actuator feedback data parameters.

### Reference Information

#### Schematic Reference

Power Steering Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Variable Effort Steering System Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the M72 Variable Effort Steering Actuator.
2. Test for less than 5 Ω between the control circuit terminal A and ground.

⇒ | If greater than the specified value, test the control circuit for a short to voltage or an open/high resistance. If circuits test normal, replace the K43 Power Steering Control Module.

3. Ignition OFF, test for less than 5 Ω between the control circuit terminal B and ground.

⇒ | If greater than the specified value, test the control circuit for a short to voltage or an open/high resistance. If circuits test normal, replace the K43 Power Steering Control Module.

4. Connect a test lamp between control circuit terminal A and control circuit terminal B.
5. Ignition ON, verify the test lamp briefly illuminates for approximately 1 s, then turns OFF.

⇒ | If the test lamp is always ON, test for a short to ground on either control circuit. If the circuits test normal, replace the K43 Power Steering Control Module.

6. If all circuits test normal, test or replace the M72 Variable Effort Steering Actuator.

### Component Testing

#### Static Test

1. Ignition OFF, disconnect the harness connector at the M72 Variable Effort Steering Actuator.
2. Test for 1.6-3.1 Ω between control terminal A and control terminal B.

⇒ | If not the specified range, replace the M72 Variable Effort Steering Actuator.

3. Test for infinite resistance between each terminal and the M72 Variable Effort Steering Actuator housing case.

⇒ | If not the specified value, replace the M72 Variable Effort Steering Actuator.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Steering Gear Replacement

• | Control Module References for power steering control module replacement, setup, and programming