OBD Guide
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P138B

Glow Plug Module System Voltage

P138B is an OBD-II diagnostic trouble code meaning: Glow Plug Module System Voltage. Common causes: glow plug module malfunction, damaged wiring or poor contacts. Estimated repair cost: $33–111.

Severity
⚠️ Medium
Can you drive?
Yes, but get it checked soon
Approx. repair cost
$33–111 (est.)

Symptoms

  • Difficulty starting the engine, especially in cold weather
  • Check Engine Light Is On
  • Reduced engine power
  • Unstable engine idling

Causes

  • Glow plug module malfunction
  • Damaged wiring or poor contacts
  • Low voltage in the on-board network
  • Faulty glow plug relay
  • Problems with the engine control unit

How to Fix

  1. Check the voltage in the vehicle's on-board network
  2. Check the integrity of the wiring and the quality of contacts
  3. Check the operation of the glow plug relay
  4. Check the glow plug module for faults
  5. If necessary, replace the glow plug module

Related codes

P138AP138CP0670

FAQ

What does the P138B code mean?

P138B is an OBD-II diagnostic trouble code that indicates: Glow Plug Module System Voltage

What causes a P138B error code?

The most common causes of P138B include: Glow plug module malfunction; Damaged wiring or poor contacts; Low voltage in the on-board network; Faulty glow plug relay.

How do I fix a P138B diagnostic trouble code?

To fix P138B: Check the voltage in the vehicle's on-board network. Check the integrity of the wiring and the quality of contacts. Check the operation of the glow plug relay. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with P138B?

Yes, but get it checked soon

How much does it cost to fix P138B?

The estimated repair cost for P138B is $33–111. Actual cost depends on your vehicle, location, and labor rates.

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See also: Russian version · NationStat