OBD-II Code
P0384
Severity
Not yet reviewed
Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.
Can you drive it
We cannot say
Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.
Indicative cost (USD)
$100–$800
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
P0384 means the glow-plug control circuit is reading HIGH — the bus voltage during the wait-to-start interval is above the expected battery-rail value (typically more than 0.5 V above battery voltage on a 12V system) or the current draw is below the floor while the module's output transistor is commanded on (an open-circuit condition reads as 'high voltage at the load').
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then follow the diagnostic notes further down this page, in the order they are written.
They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
Read the full diagnostic procedureP0384 means the glow-plug control circuit is reading HIGH — the bus voltage during the wait-to-start interval is above the expected battery-rail valu…
P0384 means the glow-plug control circuit is reading HIGH — the bus voltage during the wait-to-start interval is above the expected battery-rail value (typically more than 0.5 V above battery voltage on a 12V system) or the current draw is below the floor while the module's output transistor is commanded on (an open-circuit condition reads as 'high voltage at the load').
Cheapest-first ladder
- backprobe the glow-plug bus at the first plug and measure voltage during pre-heat — voltage above 13.8 V on a 12V system with the engine off and the module commanded on means the load isn't pulling the bus down (open bus or open plug bank).
- Clamp current at the GPCM output — under 5 A during pre-heat at coolant below 50 F is a confirmed open-circuit fault.
- Disconnect and ohm-check each plug individually — an open plug (resistance reads infinity, healthy is 0.4-2.0 ohms) breaks current draw and reports as 'high circuit voltage' even though the wiring is fine.
- Inspect the bus-bar continuity — a broken solder joint at the bus eyelet looks identical electrically to an open plug.
- Verify the wait-to-start timer is enabled — coolant temp sensor faults that report falsely high (warm engine when actually cold) bypass glow operation and can throw P0384 in a corner case. Expensive-misdiagnosis caveat: before replacing the glow-plug control module on a P0384, individually resistance-check each plug — an open plug pulls bus voltage high during commanded-on and trips the module's fault detection, but the module is fine; replacing the module without fixing the open plug sets P0384 again on the next cold start.
Vehicle-specific patterns2003-2007 Ford 6.0L Powerstroke commonly throws P0384 when a single glow plug fails open (very common at 80k+ miles) — the GPCM detects the bank's op…
- 2003-2007Ford 6.0L Powerstroke commonly throws P0384 when a single glow plug fails open (very common at 80k+ miles) — the GPCM detects the bank's open circuit and codes high; the proper fix is replacing the failed plug AND inspecting the remaining seven since they age together.
- 2008-2010Ford 6.4L Powerstroke throws P0384 from open plugs on the rear bank specifically.
- 2001-2010GM Duramax LB7-L5P throws P0384 from a known failure where one of the eight plugs corrodes at its bus terminal and breaks continuity electrically while looking fine visually.
- 2007-2014RAM Cummins 6.7L throws P0384 from individual in-head plug failures — the head heat-soaks the plug tips and they oxidize internally.
- 2010-2015VW 2.0 TDI throws P0384 from open-plug failures on the 4-plug bus; Mercedes Sprinter OM642 throws P0384 from a failed PDC-mounted module not driving the bus at all.
Estimated repair$100 to $800.
Look up another code
More free tools