Ford Codes List

Ford-enhanced trouble code lookup
for Ford, Lincoln and Mercury.

Repair Order

655 Ford-enhanced codes on file

Code
P1399

Glow Plug Circuit High Side High Input

Category
Powertrain - Fuel/Air Metering
Severity
Check Engine Light
Applies to
F-250/F-350 Super Duty diesel
Related
No single generic twin. See OBD Codes List

Findings, check these first

  • High-side feed shorted to power
  • Stuck glow plug relay
  • Wiring fault
  • Controller fault
  • Overvoltage event

Standard procedure

  1. Check for shorts to power in the feed
  2. Test relay release
  3. Inspect wiring
  4. Verify system voltage is normal
  5. Repair wiring or replace the relay

Code lookup

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Sources and review

Review: qualified. Read the source limits below.

  • OBDII.pro: P1399 Ford definition

    live reference page (obdii.pro)

    Supports: Ford-family meaning for P1399: Glow Plug Circuit High Side, High Input

    Fetched directly. obdii.pro is a publisher independent of the engine-codes family.

Last updated 2026-09-06.

Report a correction for P1399. Include your vehicle, the issue and a source if you have one.

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