P067B — Cylinder 4 Glow Plug Control Circuit High

The diagnostic trouble code P067B indicates that the vehicle’s Engine Control Unit (ECU) has detected a high voltage or abnormal signal in the control circuit of the **glow plug** for cylinder 4. *Glow plugs* are heating elements used to aid starting, especially in cold conditions, by warming the combustion chambers. The code typically points to an electrical or sensor issue within this circuit.

Note that **labeling may vary** between vehicle manufacturers, so the specific terminology used might differ, but the underlying issue remains consistent across brands.

Fast Facts

System affected: Glow Plug Control Circuit
Severity: Moderate to high, depending on symptoms and context
Main symptoms: Difficult starting, engine misfire, Check Engine light illuminated
Driveability: Limited / No / Yes (depending on severity and other factors)

Manufacturer variations for trouble code P067B

Different vehicle manufacturers may assign unique labels or codes for similar issues involving glow plug circuitry. Variations may include different coding formats or terminology, but generally they reference a problem with glow plug control circuits or specific to cylinder 4. Some known manufacturer-specific labels include:

BMW: DME fault codes referencing glow plug control, e.g., « DME fault code 119B »
Volkswagen / Audi / Seat / Skoda: « P069B » (may vary) for glow plug circuit issues
Ford: « P069B » or similar identifiers relating to glow plug control modules
Mercedes-Benz: Specific DTCs related to glow plug circuit faults, often in the format of 0x XXXX

Always consult the specific vehicle’s service documentation or manufacturer’s OBD-II code definitions for precise identification.

What does trouble code P067B mean?

In simple terms, P067B indicates that the ECU has detected an abnormal or high-voltage signal in the control circuit for the **glow plug in cylinder 4**. The ECU continually monitors the electrical circuit controlling each glow plug, which is responsible for pre-heating the cylinder to ensure smooth cold starts.

This code can be triggered by an open circuit (break in wiring), a short circuit (excessive voltage), a faulty glow plug, or issues with the electronic control module itself. It generally appears when the ECU detects that the voltage received for the control of cylinder 4’s glow plug exceeds normal parameters, suggesting a wiring fault or component malfunction.

Typically, this condition occurs during cold starts or in vehicles equipped with advanced glow plug control systems that incorporate sensors and actuators to optimize engine warm-up. When the circuit behaves unexpectedly, the ECU flags this as a fault, illuminating the check engine light and storing the code.

Severity and risks of trouble code P067B

P067B can range from a minor inconvenience to a more significant issue depending on its cause. If the glow plug circuit is malfunctioning, the vehicle may face starting difficulties, especially in cold environments. Continued operation with this fault could lead to incomplete combustion, increased emissions, or engine misfire.

In some cases, the vehicle might still start but with reduced efficiency or increased emissions. In others, you could experience problems with cold starts or even engine damage if the glow plug fails to function correctly over an extended period.

**Can the vehicle be driven?** Limited — it is possible to drive temporarily, but repairs are recommended to avoid further complications or damage.

Symptoms of trouble code P067B

The symptoms associated with this fault often relate to issues during engine startup or operation. Drivers or technicians may notice:

Hard or extended cold starts: Difficulty starting the engine in cold weather.
Engine misfires: Rough running, especially during warm-up phase.
Increased emissions: The vehicle might fail emissions testing or show higher pollutant outputs.
Glow Plug Warning Light: Sometimes the dashboard may display a glow plug indicator or check engine light.
Failure to pass cold-start diagnostics tests.

Most likely causes of trouble code P067B

If this fault appears, it’s usually caused by issues within the electrical system or relay responsible for glow plug control. Typical causes, ranked from most to less common, include:

Faulty glow plug in cylinder 4: An internal failure or open circuit in the glow plug itself can trigger this code.
Damaged or wiring issues: Broken, frayed, or corroded wiring connectors or harnesses leading to the glow plug or control module.
Control circuit malfunction: An electronic fault within the ECU, relay, or control module responsible for managing glow plug operation.
Blown fuse or relay failure: Electrical protection components may be defective or triggered.
Sensor malfunction: A defective temperature or position sensor feeding the ECU false readings.

How to diagnose trouble code P067B

Diagnosing this issue requires a systematic approach to identify whether it is a wiring problem, component failure, or control malfunction. Here are general diagnostic steps:

Visual Inspection: Check the wiring harness, connectors, and glow plug for obvious damage, corrosion, or disconnection.
Retrieve freeze frame data: Use an OBD-II scanner to see the engine’s recent electrical readings and conditions when the fault occurs.
Test the glow plug: Using a multimeter, measure the resistance of the glow plug and verify if it falls within specifications.
Inspect the wiring continuity: Perform a resistance test on wiring circuits from the ECU to the glow plug to detect breaks or shorts.
Check the control circuit voltage: With the engine off, verify the voltage signals at the control connector for abnormalities.
Test the relay and control module: Ensure relays are functioning correctly and check if the control module is providing proper signals.
Scan live data during engine startup: Monitor the glow plug circuit signals to detect anomalies or abnormal voltages.

Possible repairs for trouble code P067B

The appropriate repair depends on the root cause identified during diagnosis. Here are common repairs, listed in increasing complexity:

Replace faulty glow plug: If the glow plug shows an open circuit or resistance outside specifications. (Basic repair—requires technical knowledge)
Repair or replace wiring harness or connectors: Fix frayed wiring, corroded connectors, or poor contacts. (Basic to moderate repair, depending on access)
Check and replace relay or fuse: If a relay or fuse is blown or malfunctioning, replacing it can resolve the circuit issue. (Basic repair)
Inspect and replace control module or ECU: If the electronic control unit fails to supply correct signals, professional diagnosis and replacement may be needed. (Requires expert intervention)
Address other sensor issues: Replace temperature or position sensors that send faulty data to the ECU.

Vehicles commonly associated with trouble code P067B in Europe

This fault can occur across many vehicle brands, especially those equipped with electronically controlled glow plug systems. In Europe, common affected vehicles include:

Volkswagen Group: Models from VW, Audi, SEAT, Skoda, especially diesel engines with sophisticated glow plug management.

BMW: Particular diesel models using Bosch or Siemens control systems.

Ford: Certain diesel engine vehicles equipped with electronic glow plug control modules.

Mercedes-Benz: Specific models with advanced glow plug control circuitry integrated into engine management systems.

Frequent mistakes with trouble code P067B

Diagnosing and repairing this fault requires care; common errors can lead to prolonged issues or unnecessary repairs. Typical mistakes include:

Jumping to conclusions without visual inspection: Failing to check wiring or glow plug condition before replacing components.
Neglecting to verify control module function: Overlooking a potential ECU fault or communication issue.
Misinterpreting live data: Misreading voltages or sensor signals during diagnosis.
Forgetting safety precautions: Working with electrical components without proper precautions can cause further damage or personal injury.

Quick FAQ — trouble code P067B

Can this code disappear on its own? Yes, sometimes temporary wiring issues or sensor glitches can cause the code to clear after a drive cycle, but underlying problems often reoccur.

Can I keep driving? Limited — it’s generally safe to operate the vehicle temporarily, but ongoing issues could lead to further damage or starting difficulties; prompt diagnostics and repair are advised.

Why does the code return after clearing it? Because the root cause, such as a faulty glow plug or wiring problem, remains unaddressed, the ECU detects the fault again during subsequent drive cycles.