OBD Guide
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C1685

4WAS Main Control Unit Communication

C1685 is an OBD-II diagnostic trouble code meaning: 4WAS Main Control Unit Communication. Common causes: open or short circuit in the can communication circuit, 4was control unit malfunction. Estimated repair cost: $167–556.

Severity
🔴 High
Can you drive?
Limited driving only, diagnose soon
Approx. repair cost
$167–556 (est.)

Symptoms

  • Check Engine light comes on
  • Poor handling at high speeds
  • Disabling Active Steering
  • Possible problems with ESP and other related systems

Causes

  • Open or short circuit in the CAN communication circuit
  • 4WAS control unit malfunction
  • Problems with power supply of the 4WAS unit
  • Corrosion of contacts in connectors
  • Software errors in the ECU

How to Fix

  1. Check the integrity of the wiring harness to the 4WAS unit
  2. Check the power and ground of the 4WAS unit
  3. Inspect connectors for corrosion
  4. Read error codes from the 4WAS block
  5. If necessary, replace the 4WAS control unit
  6. Update ECU software

Related codes

U0100U0121C1686

FAQ

What does the C1685 code mean?

C1685 is an OBD-II diagnostic trouble code that indicates: 4WAS Main Control Unit Communication

What causes a C1685 error code?

The most common causes of C1685 include: Open or short circuit in the CAN communication circuit; 4WAS control unit malfunction; Problems with power supply of the 4WAS unit; Corrosion of contacts in connectors.

How do I fix a C1685 diagnostic trouble code?

To fix C1685: Check the integrity of the wiring harness to the 4WAS unit. Check the power and ground of the 4WAS unit. Inspect connectors for corrosion. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with C1685?

Limited driving only, diagnose soon

How much does it cost to fix C1685?

The estimated repair cost for C1685 is $167–556. Actual cost depends on your vehicle, location, and labor rates.

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