P0383
Fix within a few daysGlow Plug/Heater Circuit 'C' Low Input
Code P0383 means the glow plug circuit for cylinder C has a low voltage input. Common causes: Faulty glow plug C (60%), GPCM (25%), wiring (10%). Drivability: Yes, for short trips only. Repair cost: $20-$400 DIY, $150-$800 professional.
Can I Drive With P0383?
Yes, for short trips only
Essential trips under 10 miles, avoid highways if engine runs rough
Stop driving immediately if: Engine will not start at all, excessive white smoke, significant power loss
Symptoms of P0383
- 1Hard starting, especially in cold weather
- 2Rough idle immediately after a cold start
- 3White smoke from the exhaust on cold start
- 4Engine cranking longer than usual before starting
- 5Reduced fuel economy
Common Causes of P0383
Parts most likely causing this code, ranked by probability
A faulty glow plug in cylinder C, often an open circuit or internal short, causes a low voltage reading in its circuit.
60% of P0383 cases are fixed by replacing the glow plug for cylinder C
The GPCM or its internal relay can fail, preventing proper voltage delivery to the glow plug circuit.
25% of P0383 cases are fixed by replacing the Glow Plug Control Module
Damaged, corroded, or shorted wiring in the glow plug C circuit causes an incorrect voltage signal to the engine computer.
10% of P0383 cases are fixed by repairing the wiring harness
A rare internal fault in the ECM/PCM can incorrectly interpret the glow plug circuit voltage or fail to command the GPCM correctly.
5% of P0383 cases are fixed by replacing the ECM/PCM
Check These First (Before Buying Parts)
- Visually inspect the glow plug C wiring and connector for any obvious damage, corrosion, or loose connections.
- If accessible, gently wiggle the glow plug C wire to see if it's loose or if the code changes.
How to Diagnose P0383
- 1Visually inspect the glow plug C wiring and connector for damage or corrosion.
- 2Using a multimeter, check the resistance of glow plug C. Compare to specifications (usually 0.5-2.0 ohms). An open circuit (infinite resistance) or short (0 ohms) indicates a bad plug.
- 3With a test light or multimeter, check for voltage at the glow plug C connector during the cold start pre-heat cycle. No voltage indicates a GPCM or wiring issue.
- 4If glow plug C tests good, test the Glow Plug Control Module (GPCM) according to manufacturer specifications, often involving checking input and output voltages.
- 5If all other components test good, consider professional diagnosis for the ECM/PCM.
P0383 on Popular Vehicles
Ford F-Series (Powerstroke)
2003-2024On Powerstroke engines, the Glow Plug Control Module (GPCM) is a common failure point, often leading to P0383 or related glow plug codes. Glow plug replacement can be challenging due to engine design.
55% fixed by GPCM, 30% by glow plug
Chevrolet Silverado / GMC Sierra (Duramax)
2001-2024Duramax engines are known for glow plug failures, especially as mileage increases. The glow plug controller can also fail, but individual glow plugs are a more frequent cause of P0383.
65% fixed by glow plug, 20% by GPCM
Ram 2500/3500 (Cummins)
2007-2024Cummins engines are robust, but glow plug issues, including P0383, do occur. Wiring harness damage due to heat or abrasion is a notable cause in some cases, alongside individual glow plug failures.
60% fixed by glow plug, 15% by wiring harness
Frequently Asked Questions
What does P0383 mean?
P0383 indicates that the engine computer has detected a low voltage input in the glow plug circuit for cylinder 'C'. This means the glow plug for that cylinder is not receiving or drawing the correct amount of power.
Can I drive with P0383?
Yes, for short trips only. You can drive with P0383, but expect hard starting, especially in cold weather. Continued driving without repair can lead to increased emissions and potential damage to other components if the engine struggles to start or runs rough.
Will P0383 clear itself?
No, P0383 will not clear itself. The underlying electrical fault with the glow plug, control module, or wiring must be repaired. After the repair, you will need to clear the code with an OBD-II scan tool.
How do I fix P0383 myself?
Start by checking the glow plug for cylinder C. Test its resistance with a multimeter. If it's faulty, replace it. If the glow plug is good, test the Glow Plug Control Module (GPCM) and inspect the wiring harness for damage or corrosion. Repair or replace any faulty components.
How much does it cost to fix P0383?
DIY repair costs range from $20 for a single glow plug to $400 for a Glow Plug Control Module. Professional repair costs typically range from $150 to $800, depending on the part needing replacement and labor involved for access.
P0383 keeps coming back - why?
P0383 keeps coming back if the root cause was not correctly identified or fully repaired. This often happens if only one glow plug was replaced when the Glow Plug Control Module was the actual issue, or if a wiring problem was overlooked. Ensure all components in the circuit are thoroughly tested.
Will P0383 fail emissions/smog test?
Yes, P0383 will cause your vehicle to fail an emissions or smog test. A check engine light is an automatic failure in most jurisdictions, and a faulty glow plug can lead to increased particulate matter and unburned fuel emissions, especially during cold starts.
What's the difference between P0383 and P0380?
P0383 specifically indicates a low input issue with the glow plug circuit for cylinder 'C'. P0380 is a more general code for 'Glow Plug/Heater Circuit 'A' Malfunction', which can refer to a broader issue with the entire glow plug system or a specific bank, rather than a single cylinder's low input.
P0383 on Ford F-250/F-350 Powerstroke
On Ford Powerstroke engines (6.0L, 6.4L, 6.7L), P0383 often points to a failed glow plug or a faulty Glow Plug Control Module (GPCM). The GPCM is a common failure point on these trucks. Accessing glow plugs on some Powerstroke engines can be labor-intensive.
Questions to Ask Your Mechanic
Did you check the resistance of the glow plug for cylinder C?
Good answer: Yes, I measured the resistance, and it was outside the specified range, indicating a faulty glow plug. I also checked the wiring for continuity.
What were the voltage readings at the glow plug C connector during the pre-heat cycle?
Good answer: I saw no voltage at the connector, which led me to test the Glow Plug Control Module. The module was not sending power to that circuit.
Did you inspect the wiring harness for any signs of damage or corrosion leading to glow plug C?
Good answer: Yes, I thoroughly inspected the wiring from the GPCM to the glow plug. There was a section with frayed insulation causing a short to ground.
Repair Cost Estimate
DIY Repair
Parts only
$20-$400
Shop Repair
Parts + labor
$150-$800
Save $130-$400 by doing it yourself
Difficulty
intermediate
Time
1-4 hours
Intermediate - requires electrical testing with a multimeter and potentially challenging access to glow plugs on some engines.
Cost of Waiting
Ignoring P0383 leads to increasingly difficult cold starts, especially in winter. This puts extra strain on your starter and battery. Persistent rough idling on cold starts increases unburned fuel emissions and can prematurely clog your diesel particulate filter (DPF), which is a $1,500-$3,000 repair.
While You're In There...
If one glow plug has failed, others are likely nearing the end of their lifespan. Replacing them all at once saves labor, especially if access is difficult.
If the wiring is brittle or corroded, replacing the entire harness for that bank ensures a reliable connection and prevents future wiring-related codes.
Tools You'll Need
- OBD-II Scan Tool
- Multimeter
- Glow Plug Socket Set
- Ratchet and Extensions
- Torque Wrench
- Wire Brush (for cleaning connections)
- Dielectric Grease
P0383 is a common diesel engine code. Most repairs involve replacing a single glow plug or the control module, which are straightforward fixes that restore reliable cold starting.
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Your Next Steps
Step 1: Visually inspect the wiring and connector for glow plug C. Look for fraying, burns, or corrosion. Clean any dirty connections.
Step 2: Use a multimeter to test the resistance of glow plug C. If it's open or shorted, replace the glow plug. If the glow plug tests good, proceed to test the Glow Plug Control Module (GPCM).
Step 3: If the GPCM is faulty, replace it. If both the glow plug and GPCM test good, carefully inspect the entire wiring harness for glow plug C for any breaks or shorts.