C059A: Power Steering Control Module - Rear Missing Calibration

What it means

The rear power steering control module monitors whether its required calibration data is available. It sets this code when that calibration is missing.

At a glance

• Usually lights the ABS or stability-control warning light
• The engine or gearbox may go into limp mode

How it works

The rear power steering control module depends on calibration data for its rear steering functions. C059A sets when that required data is missing, commonly after module replacement or related service, or when setup was not completed successfully.

Common causes

Most likely first.

1. Calibration not performed after module replacement or service
2. Calibration procedure incomplete
3. Module configuration issue

Symptoms

• ABS warning light on
• ESC/stability control deactivated
• Possible reduced brake assist
• Speedometer may behave erratically

How to diagnose it

1. Scan the steering and chassis modules, record fault details, and check for other codes that could block calibration or module communication.
2. Review recent work and confirm that the rear power steering module is configured for the vehicle and its required calibration is known.
3. Check the rear module’s power, ground, connector, and communication status before attempting setup.
4. Use a capable scan tool to check calibration status and run the manufacturer-specified rear module learning procedure.
5. Rescan the system and confirm that calibration is stored and the fault does not return.

Common fixes

• Complete the required rear power steering module calibration with a compatible scan tool.
• Repeat an interrupted or incomplete calibration after addressing any reported blocking fault.
• Correct the module configuration or software if vehicle service information identifies an issue.
• Replace the rear module only if testing confirms that it cannot retain or use its calibration.

Can I keep driving?

The rear steering system may not operate as intended, and the listed brake or stability warnings may indicate related systems are affected. Avoid driving if steering response or braking is abnormal, and arrange an inspection before further use.