P1399: Glow Plug Circuit High Side, High Input
Methodology: We combine code standards with complaint and reliability patterns, then review for clear, vehicle-first diagnosis steps.
Sources: SAE/OBD-II definitions, manufacturer service information, and public reliability reports (including NHTSA where applicable).
Limits: Guidance is informational and may not match every model-year or revision. Confirm with the official manual and diagnostics before replacing parts. For safety-critical or electrical work, use a qualified technician.
What Does P1399 Mean?
P1399 is a diagnostic trouble code indicating: Glow Plug Circuit High Side, High Input. This code relates to the manufacturer-specific powertrain system. The vehicle's computer detected a condition outside normal operating parameters and stored this code.
Symptoms of P1399
- ⚠️ Check Engine Light (MIL) illuminated
- ⚠️ Glow Plug reading stuck at maximum value
- ⚠️ Related system operating erratically or in default mode
- ⚠️ Reduced engine performance
Common Causes
- 🔍 Short to voltage in Glow Plug wiring harness
- 🔍 Corroded or water-damaged Glow Plug connector
- 🔍 Faulty Glow Plug outputting maximum voltage
- 🔍 Damaged wiring rubbing against metal components
- 🔍 ECM/PCM internal fault (rare)
Frequently Asked Questions
What does P1399 mean?
Can I drive with code P1399?
How much does it cost to fix P1399?
What To Do Next
Possible Fixes
- 🔧 Inspect and repair Glow Plug wiring for short to voltage
- 🔧 Clean or replace corroded Glow Plug connector
- 🔧 Replace faulty Glow Plug
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1
Find your vehicle above
Click your make and model for real owner reports and common causes specific to your vehicle.
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2
Check for recalls
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.
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Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.