P268E

Cylinder 12 Glow Plug Circuit Low

P268E is a generic OBD-II powertrain diagnostic trouble code: Cylinder 12 Glow Plug Circuit Low. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P268E
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
Need P268E disabled?
RaceTune permanently disables any OBD-II trouble code on supported ECUs — for motorsport, off-road, and export use.
→

What P268E means

P268E is the cylinder 12 equivalent of the individual glow plug low circuit fault series. It is set when the glow plug control module detects insufficient current flow or abnormally low voltage on the circuit feeding the glow plug for cylinder 12. Like P268B for cylinder 11, this code applies to large multi-cylinder diesel engines where individual plug circuit monitoring is implemented.

An open-circuit glow plug is the most frequent cause, followed by wiring damage between the module and the plug. On engines where glow plugs are mounted in difficult-to-access locations, connector corrosion is a common contributing factor. The control module compares expected current draw against actual measured current and sets this code when the difference indicates an open or near-open circuit.

The functional consequence is the same as other individual glow plug faults: reduced preheating on that cylinder, which can cause a minor cold-start rough condition and slightly elevated cold-start emissions. On a healthy otherwise full-complement engine, the impact is minor in warm climates but more noticeable in cold conditions. The repair is straightforward once the open circuit is confirmed.

Common causes

Most-frequently reported root causes when P268E is logged.

  • 1
    Failed open-circuit glow plug in cylinder 12.
  • 2
    Damaged or open wiring harness on the cylinder 12 glow plug feed circuit.
  • 3
    Corroded glow plug terminal or connector pin on cylinder 12.
  • 4
    High contact resistance at a harness splice or bus bar feeding cylinder 12.
  • 5
    Glow plug control module driver fault on the cylinder 12 output channel.
  • 6
    Thermal fuse or protection device failure in the cylinder 12 circuit.

Symptoms drivers notice

MIL and possibly a glow plug warning light on.
Minor rough running or misfiring on cylinder 12 during cold start and warm-up.
Marginal cold-starting ability in very cold ambient temperatures.
Slight increase in exhaust white smoke immediately after a cold start.
Symptom may be imperceptible in warm ambient conditions.

How to diagnose P268E

A typical diagnostic flow when this code is present.

  1. 1
    Read all DTCs; document any additional glow plug circuit codes for other cylinders.
  2. 2
    Inspect the cylinder 12 glow plug connector and terminal for corrosion, looseness, or damage.
  3. 3
    Disconnect the glow plug and measure its resistance; an open circuit or resistance significantly above specification indicates a failed plug.
  4. 4
    Check continuity of the wiring between the glow plug module and cylinder 12 terminal.
  5. 5
    If wiring and plug are good, measure the module output current on the cylinder 12 channel during a commanded glow activation using a current clamp.
  6. 6
    Replace the glow plug or repair wiring as indicated by the measurements.
  7. 7
    Clear codes and perform a cold-start verification test.

Related powertrain codes

Frequently asked questions

Is P268E different from P268B other than the cylinder number?

Functionally they are identical faults on different cylinders. The diagnostic approach is the same; only the physical location of the glow plug changes.

Can this code cause a no-start on a large diesel?

A single failed plug on a 12-cylinder engine rarely causes a no-start on its own, but multiple simultaneous failures or very cold conditions could contribute to starting difficulty.

How long do glow plugs typically last?

Service life varies widely by engine type and duty cycle, but many manufacturers suggest inspection or replacement at major service intervals. Plugs used for both pre-glow and post-glow heating wear faster.

Does this code affect power output?

Not directly. Once the engine is fully warmed up, glow plugs are not in use and power output is unaffected. The impact is limited to cold-start quality.

Disabling P268E in software

RaceTune can permanently disable P268E — 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.

ECUs with a P268E disable in our catalogue

Confirmed coverage from our recipe database — we support many more families. Upload your file and our identifier will match it automatically.

  • Bosch EDC17CP09 verified 1 software version

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.

Got P268E in your scan?

Upload your ECU file — we'll identify the exact software version and confirm whether a disable is available for your car.

Upload your file