C0203 moderate

Adaptive Cruise Control Radar Sensor Malfunction

The C0203 code means the vehicle's onboard diagnostic system has detected: Adaptive Cruise Control Radar Sensor Malfunction. This is a moderate severity code.

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Keep driving?: Yes, but fix soon
DIY difficulty: hard
Estimated cost: $100 - $2,000 (parts and labor)

Read ABS Codes

BlueDriver Bluetooth Pro Scanner

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Read ABS Codes

LAUNCH CRP123X (Reads ABS + Chassis)

Basic scanners cannot read ABS codes. This one reads all four systems so you know exactly which sensor failed.

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Common Symptoms

Adaptive cruise control not available
Radar sensor blocked warning message
Forward collision warning disabled
ACC system fault on dashboard
Distance display to vehicle ahead not showing

Probable Causes (Ranked by Likelihood)

Radar sensor blocked by dirt, snow, or ice Very High
Radar sensor out of alignment from bumper impact High
Failed radar sensor unit Moderate
Radar sensor wiring or connector fault Low

Step-by-Step Diagnostic Procedure

Clean radar sensor area on front bumper or grille
Inspect for bumper damage that could misalign sensor
Scan ACC module for sensor DTCs
Check radar sensor connector for damage
Perform radar sensor alignment if recently impacted

Frequently Asked Questions

Where is the radar sensor located?

The adaptive cruise control radar sensor is typically mounted in the front bumper, behind the grille emblem, or behind a cover plate in the lower bumper area.

Can a bumper repair affect the radar sensor?

Yes. Even minor bumper work can misalign the radar sensor. After any front-end repair, the sensor should be recalibrated using a specialized alignment target and scan tool.

Why does the sensor warning come on in bad weather?

Heavy rain, snow, or ice buildup on the sensor face can block the radar signal. The system will display a warning and disable ACC until the sensor is clear.