OBD Guide
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C1939

Brake Pressure Switch Input Circuit Failure

C1939 is an OBD-II diagnostic trouble code meaning: Brake Pressure Switch Input Circuit Failure. Common causes: open or short circuit in wiring harness, brake pressure sensor malfunction. Estimated repair cost: $56–167.

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

Symptoms

  • ABS or ESP indicator is on
  • Reduced braking performance
  • Disabling Brake Assist Systems

Causes

  • Open or short circuit in wiring harness
  • Brake pressure sensor malfunction
  • Poor contact in connectors
  • Malfunction of the ABS/ESP control unit

How to Fix

  1. Check the integrity of the wiring harness and connectors
  2. Check the resistance of the brake pressure sensor
  3. Replace brake pressure sensor if necessary
  4. Check and reflash the ABS/ESP control unit

Related codes

C1940C1941C1942

FAQ

What does the C1939 code mean?

C1939 is an OBD-II diagnostic trouble code that indicates: Brake Pressure Switch Input Circuit Failure

What causes a C1939 error code?

The most common causes of C1939 include: Open or short circuit in wiring harness; Brake pressure sensor malfunction; Poor contact in connectors; Malfunction of the ABS/ESP control unit.

How do I fix a C1939 diagnostic trouble code?

To fix C1939: Check the integrity of the wiring harness and connectors. Check the resistance of the brake pressure sensor. Replace brake pressure sensor if necessary. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with C1939?

Limited driving only, diagnose soon

How much does it cost to fix C1939?

The estimated repair cost for C1939 is $56–167. Actual cost depends on your vehicle, location, and labor rates.

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See also: Russian version · NationStat