P268B

Cylinder 11 Glow Plug Circuit Low

P268B is a generic OBD-II powertrain diagnostic trouble code: Cylinder 11 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
P268B
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
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What P268B means

P268B is stored when the glow plug control system detects a low voltage or low current condition on the glow plug circuit for cylinder 11. This code is most relevant on large displacement diesel engines with 12 or more cylinders, such as heavy-duty commercial vehicle engines. The control module monitors each individual glow plug circuit and flags a fault when the measured current or voltage falls below expected values during a glow cycle.

A low circuit condition on cylinder 11 typically points to an open-circuit glow plug, a broken wire between the control module and the plug, or a poor connection at the glow plug terminal. Because each plug is individually monitored in modern systems, a single faulty plug can be isolated and replaced without affecting the rest of the system.

The effect on starting depends on ambient temperature and how many cylinders are affected. A single failed plug on an otherwise healthy 12-cylinder engine may have minimal impact in mild weather but will contribute to rough cold-start and increased emissions in cold conditions. Diagnosis should confirm the open circuit location before parts replacement.

Common causes

Most-frequently reported root causes when P268B is logged.

  • 1
    Open-circuit or failed glow plug in cylinder 11.
  • 2
    Broken or disconnected wiring between the glow plug module and cylinder 11 plug.
  • 3
    Corroded or loose glow plug terminal connection.
  • 4
    High-resistance connection at the glow plug bus bar or harness splice for cylinder 11.
  • 5
    Glow plug control module output driver fault for the cylinder 11 channel.
  • 6
    Blown fuse or thermal protection device in the cylinder 11 glow plug supply path.

Symptoms drivers notice

MIL illuminated, possibly with a glow plug warning light.
Slightly rough cold start or minor misfire on cylinder 11 during warm-up.
Marginal cold-starting performance in very low ambient temperatures.
Possible minor increase in white smoke during cold start.
No noticeable symptom in warm ambient conditions.

How to diagnose P268B

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool and retrieve all DTCs; check for additional individual cylinder glow plug codes.
  2. 2
    Locate the cylinder 11 glow plug and inspect the terminal for corrosion or looseness.
  3. 3
    Disconnect the glow plug connector and measure glow plug resistance; an open circuit or very high resistance indicates a failed plug.
  4. 4
    Inspect the wiring between the glow plug module and the cylinder 11 plug for damage or open circuits.
  5. 5
    If the plug resistance is within specification, check the glow plug module output for cylinder 11 by monitoring current during a commanded glow cycle.
  6. 6
    Replace the glow plug if found open or out of specification.
  7. 7
    Clear DTCs and verify correct operation with a cold-start test.

Vehicles where we've handled P268B

Platforms in our catalogue with confirmed P268B coverage.

BMW 320D
2016

Related powertrain codes

Frequently asked questions

What engine types would have a cylinder 11 glow plug?

Engines with 12 or more cylinders, such as large commercial diesel V12 or inline-12 configurations found in heavy trucks, buses, and industrial equipment.

Can I replace just the cylinder 11 glow plug, or do I need to do all of them?

You can replace only the failed plug. However, if the engine has high mileage and plugs have not been replaced before, replacing all plugs at the same service is often recommended to avoid subsequent failures.

Is P268B a critical fault?

Generally not critical on multi-cylinder engines in mild weather, but it should be repaired to maintain cold-start reliability and emissions compliance.

Could a loose glow plug terminal cause this code without the plug itself being bad?

Yes. A loose or corroded terminal creates a high-resistance connection that the control module interprets as a low or open circuit. Always clean and tighten the terminal before condemning the plug.

Disabling P268B in software

RaceTune can permanently disable P268B — 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 P268B 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 EDC17C50 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.

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