OBD Guide
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B138A

Control Module Voltage Reference Output Circuit

B138A is an OBD-II diagnostic trouble code meaning: Control Module Voltage Reference Output Circuit. Common causes: open or short circuit in the reference voltage circuit, poor contact in connectors. Estimated repair cost: $56–167.

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

Symptoms

  • Incorrect engine operation
  • Check Engine Light Illuminates
  • Problems with sensor operation

Causes

  • Open or short circuit in the reference voltage circuit
  • Poor contact in connectors
  • Control module malfunction

How to Fix

  1. Check the integrity of the wiring in the reference voltage circuit
  2. Check the contacts in the control module and sensor connectors
  3. Test the control module for faults
  4. Replace damaged components

Related codes

B138BB138CP0601

FAQ

What does the B138A code mean?

B138A is an OBD-II diagnostic trouble code that indicates: Control Module Voltage Reference Output Circuit

What causes a B138A error code?

The most common causes of B138A include: Open or short circuit in the reference voltage circuit; Poor contact in connectors; Control module malfunction.

How do I fix a B138A diagnostic trouble code?

To fix B138A: Check the integrity of the wiring in the reference voltage circuit. Check the contacts in the control module and sensor connectors. Test the control module for faults. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with B138A?

Limited driving only, diagnose soon

How much does it cost to fix B138A?

The estimated repair cost for B138A is $56–167. Actual cost depends on your vehicle, location, and labor rates.

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See also: Russian version · NationStat