Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that the car's computer has detected a problem with the glow plugs, which are parts that help start the engine in cold weather. It's like when you try to use a flashlight, and it doesn't turn on because the batteries are not working right.
The P1399 code indicates an issue with the electrical circuit that controls the glow plugs, which are used to heat the engine cylinders for starting in cold conditions.
The glow plug circuit high side, high input code P1399 is triggered when the Engine Control Module (ECM) detects a voltage level that is higher than expected in the glow plug circuit. This could be due to an open circuit, a faulty glow plug, or a problem with the control module itself.
• Hard starting in cold weather
• Check engine light on
• Rough idle when cold
• Faulty glow plug
• Open or shorted glow plug circuit
• Faulty Engine Control Module (ECM)
Glow Plug: A device used to heat the cylinders of a diesel engine to aid in starting.
ECM: Engine Control Module, the computer that controls engine functions.
• Check the glow plugs for continuity.
• Inspect the wiring and connectors for damage.
• Test the ECM for proper function.
• Replace faulty glow plugs.
• Repair or replace damaged wiring.
• Replace the ECM if necessary.
• Multimeter
• OBD-II scanner
• Screwdriver set
$100 - $500
Moderate
• Ford F-Series
• Chevrolet Silverado
• Dodge Ram
• Regularly inspect glow plugs.
• Maintain proper battery health.
• Ensure wiring is intact and free from corrosion.
Sensor Issue
• Have the vehicle inspected by a professional if the check engine light is on.
• Avoid driving in extremely cold conditions until the issue is resolved.
Check with your vehicle manufacturer for specific warranty coverage on engine components.
The P1399 code has been reported in diesel engines, particularly in older models where glow plug systems are more prevalent.
Moderate – It is important to address this issue to prevent starting problems, especially in cold weather.
Driving with a malfunctioning glow plug system can lead to increased emissions and potential engine damage.
• Engine cold start
• Ambient temperature below freezing
Glow plugs are typically located in the cylinder head of diesel engines.
Q: What happens if I ignore the P1399 code?
A: Ignoring this code can lead to hard starting and potential engine damage in cold weather.
Q: Can I drive my car with a P1399 code?
A: While you may be able to drive, it is not recommended, especially in cold conditions, as the engine may not start properly.
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