OBD Guide
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C1805

Mismatched PCM and/or ABS Module

C1805 is an OBD-II diagnostic trouble code meaning: Mismatched PCM and/or ABS Module. Common causes: pcm and abs software mismatch, replacing the pcm or abs module without adaptation. Estimated repair cost: $56–167.

Severity
⚠️ Medium
Can you drive?
Limited driving only, diagnose soon
Approx. repair cost
$56–167 (est.)

Symptoms

  • Check Engine light comes on
  • Unstable ABS operation
  • Loss of engine power
  • Incorrect speedometer readings

Causes

  • PCM and ABS software mismatch
  • Replacing the PCM or ABS module without adaptation
  • Damage to the wiring harness between modules
  • Problems with power supply or grounding of modules

How to Fix

  1. Check wiring harness for damage
  2. Check connections and contacts of PCM and ABS modules
  3. Update module software
  4. Perform module adaptation using diagnostic equipment
  5. If necessary, replace the faulty module

Related codes

C1800C1801U0100

FAQ

What does the C1805 code mean?

C1805 is an OBD-II diagnostic trouble code that indicates: Mismatched PCM and/or ABS Module

What causes a C1805 error code?

The most common causes of C1805 include: PCM and ABS software mismatch; Replacing the PCM or ABS module without adaptation; Damage to the wiring harness between modules; Problems with power supply or grounding of modules.

How do I fix a C1805 diagnostic trouble code?

To fix C1805: Check wiring harness for damage. Check connections and contacts of PCM and ABS modules. Update module software. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with C1805?

Limited driving only, diagnose soon

How much does it cost to fix C1805?

The estimated repair cost for C1805 is $56–167. Actual cost depends on your vehicle, location, and labor rates.

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