OBD Guide
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P1399

Glow Plug Circuit High Side, High Input

P1399 is an OBD-II diagnostic trouble code meaning: Glow Plug Circuit High Side, High Input. Common causes: short circuit in glow plug circuit, faulty glow plug relay. Estimated repair cost: $17–89.

Severity
⚠️ Medium
Can you drive?
Yes, but get it checked soon
Approx. repair cost
$17–89 (est.)

Symptoms

  • Difficulty starting the engine (especially in cold weather)
  • Check Engine Light Is On
  • Reduced engine power
  • Increased fuel consumption
  • Unstable operation at idle

Causes

  • Short circuit in glow plug circuit
  • Faulty glow plug relay
  • Damaged wiring or poor contacts
  • Problems with the glow plug control module
  • Faulty Engine Control Unit (ECU)

How to Fix

  1. Check glow plug circuit fuses
  2. Check glow plug relay for short circuit
  3. Inspect the wiring harness for damage
  4. Check the resistance of the glow plugs
  5. Check the operation of the glow plug control module or ECU

Related codes

P0380P0670P0671

Error P1399 by Vehicle Brand

BuickCadillacChevroletChryslerDodgeFordGMGMCJeepLincolnMercuryOldsmobilePlymouthPontiacSaturnVolkswagen

FAQ

What does the P1399 code mean?

P1399 is an OBD-II diagnostic trouble code that indicates: Glow Plug Circuit High Side, High Input

What causes a P1399 error code?

The most common causes of P1399 include: Short circuit in glow plug circuit; Faulty glow plug relay; Damaged wiring or poor contacts; Problems with the glow plug control module.

How do I fix a P1399 diagnostic trouble code?

To fix P1399: Check glow plug circuit fuses. Check glow plug relay for short circuit. Inspect the wiring harness for damage. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with P1399?

Yes, but get it checked soon

How much does it cost to fix P1399?

The estimated repair cost for P1399 is $17–89. Actual cost depends on your vehicle, location, and labor rates.

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