P06C6

Cylinder 2 Glow Plug Incorrect

P06C6 is a generic OBD-II powertrain diagnostic trouble code: Cylinder 2 Glow Plug Incorrect. It is logged by the engine control unit when the glow monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P06C6
Group
Powertrain
System
Glow
Severity
Warning (MIL on)
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What P06C6 means

P06C6 indicates that the engine control module has judged the glow plug on cylinder 2 to be the wrong plug, because its measured resistance sits outside the range the calibration expects. It is a generic diesel powertrain code, but it turns up most frequently on Volkswagen and Audi TDI engines whose ECUs run an explicit glow plug identification routine.

Glow plugs are resistive heaters that warm each combustion chamber so a cold diesel can ignite fuel on compression alone. A glow plug control module energises the plugs individually and reports each channel's electrical behaviour to the ECU. A short time after the ignition is switched on, the ECU asks the module to verify that every plug's resistance matches the expected type. When the cylinder 2 reading comes back too high or too low, the ECU records P06C6.

The code can reflect a real hardware problem or a measurement artefact. Real causes include an aged or partly failed plug, a corroded terminal or connector, damaged wiring, and non-genuine plugs of the wrong specification fitted during earlier service. The artefact case is well documented: Volkswagen issued a bulletin explaining that if the engine is cranked while the identification check is still running, the resulting drop in system voltage can make the ECU misread the plugs and store incorrect-glow-plug codes across cylinders 1 to 4 even though the hardware is sound.

Common causes

Most-frequently reported root causes when P06C6 is logged.

  • 1
    Non-genuine or wrong-specification glow plugs were fitted to the engine, including cylinder 2.
  • 2
    The engine was cranked during the ECU's glow plug identification check, producing a false reading.
  • 3
    The cylinder 2 glow plug has aged and its resistance has drifted out of the calibrated window.
  • 4
    A corroded or loose glow plug terminal or connector adds resistance to the measured circuit.
  • 5
    Chafed, heat-damaged or partially broken harness wiring to cylinder 2.
  • 6
    Low battery state of charge or a weak charging system reduces voltage during the check.
  • 7
    A degraded channel or outdated software level in the glow plug control module misreports the plug.
  • 8
    Poor ground connections at the engine or the glow plug control module distort the measurement.

Symptoms drivers notice

The check engine light comes on, often after a start where the key was cranked immediately.
The engine cranks longer than normal before firing when cold.
Uneven or lumpy idle for the first seconds after a cold start.
Extra white or grey smoke from the exhaust during warm-up.
A short misfire or slight lack of power until the engine reaches operating temperature.
Frequently no noticeable drivability problem at all, only the stored fault and warning light.

How to diagnose P06C6

A typical diagnostic flow when this code is present.

  1. 1
    Read all stored codes and check whether other cylinders logged incorrect-glow-plug faults in the same session, which suggests a check-phase misread rather than multiple failed plugs.
  2. 2
    Ask the owner about their starting habit, because cranking during the first couple of seconds after ignition on is a documented cause of these codes.
  3. 3
    Measure battery state of charge and charging system output before suspecting components.
  4. 4
    Inspect the cylinder 2 glow plug terminal, its connector and the harness for corrosion, oil contamination, chafing or a loose push-on cap.
  5. 5
    Clear the fault, restart while waiting through the glow phase without cranking early, and see whether the code returns.
  6. 6
    Compare the cylinder 2 channel with the other cylinders using scan-tool live data or the glow plug test function.
  7. 7
    Only if the code repeats with correct starting technique, measure the cylinder 2 plug's resistance against a known-good plug and check for a control-module software update before replacing anything.

Related powertrain codes

Frequently asked questions

Can I keep driving with P06C6?

Generally yes. The fault affects cold starting rather than normal running, and on some vehicles it is a measurement error rather than a broken part. Have it diagnosed anyway, because a genuinely weak glow plug means harder cold starts and more cold-start smoke.

Should the glow plug be replaced because of this code?

Not on the code alone. Volkswagen's guidance for incorrect-glow-plug faults on cylinders 1 to 4 is explicitly not to replace parts before confirming the fault, because cranking during the ECU's plug check can set it falsely. Clear it, start the car properly, and see whether it comes back.

Will P06C6 fail an emissions test?

An illuminated check engine light fails an OBD emissions inspection in most regions, whatever the underlying code, so it must be fixed and cleared before testing.

Is this an expensive repair?

Often it costs nothing beyond diagnosis, because the fix can simply be a cleaned connector, a software update or a change in starting technique. If a plug does need replacing, the part itself is inexpensive and cylinder 2 is usually reasonably accessible on a four-cylinder diesel.

Disabling P06C6 in software

RaceTune can permanently disable P06C6 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

ECU families we can disable P06C6 on

We hold the DaVinci A2L disable definitions for these families, so the exact P06C6 path and mask addresses are mapped. verified marks a confirmed disable definition. We support many more — upload your file and our identifier will match it automatically.

  • Bosch EDC17C74 verified
  • Bosch EDC17CP44 verified
  • Bosch MD1CP002 verified
  • Bosch MD1CP004 verified
  • Bosch MD1CS001 verified

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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