What Does P0382 Mean?
The ECM has detected a malfunction in the glow plug or heater indicator circuit, specifically related to performance or a secondary fault condition. On some systems this code distinguishes between the glow plug heater element and the exhaust after-treatment heater. The driver may notice the glow plug warning light behaving abnormally, hard cold starting, or extended idle rough running when cold. The actual glow plug heating function may be partially or fully compromised.
Common Causes
30%
Failed glow plug relay with welded contacts causing the circuit to remain energized continuously
25%
Glow plug timer or control module malfunction affecting cycle timing
20%
Wiring fault causing the indicator circuit to read out of expected parameters
15%
Intake air heater element failure (on vehicles equipped with intake heaters)
10%
ECM coolant temperature sensor reading inaccurately, causing incorrect glow plug timing strategy
Diagnostic Steps
1
Monitor glow plug cycle timing with a scan tool. Command a glow cycle and verify the on-time matches the expected duration for the current coolant temperature (longer when cold, shorter or none when warm). Abnormal timing indicates a GPCM or ECM fault.
2
Check the glow plug relay with a clamp-on ammeter. Verify current flow starts and stops correctly during the glow cycle. A relay with welded contacts will show continuous current draw even after the cycle should end.
3
Verify the engine coolant temperature sensor reading matches actual coolant temperature (use an infrared thermometer). An inaccurate ECT reading can cause the ECM to run glow plugs incorrectly (too long, too short, or not at all).
4
If the vehicle has an intake air heater, test the heater element resistance (typically 0.5-5.0 ohms) and verify the heater relay activates on command. Check for power and ground at the heater element connector.
5
Review the glow plug control module data for fault history and individual cylinder glow plug status. Many modern GPCM modules track individual plug performance and will flag the specific failed component.
Estimated Repair Cost
$80 - $550
Parts + labor, varies by vehicle and location
The ECM has detected a malfunction in the glow plug or heater indicator circuit, specifically related to performance or a secondary fault condition. On some systems this code distinguishes between the glow plug heater element and the exhaust after-treatment heater. The driver may notice the glow plu...
The most common cause of P0382 (Glow Plug/Heater Indicator Circuit Malfunction) is: Failed glow plug relay with welded contacts causing the circuit to remain energized continuously
Typical repair costs for P0382 range from $80 to $550, depending on the vehicle, location, and whether you do it yourself or go to a shop.
If the relay is stuck on, glow plugs may overheat and burn out prematurely, or in extreme cases damage the combustion chamber. If the relay is stuck off, cold starting will be difficult. Have the fault diagnosed soon; if the glow plug light stays on constantly, repair is more urgent.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0382 to identify the root cause.
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Quick Info
Category
Powertrain
System
Diesel Glow Plug / Cold Start System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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