Faulty glow plug on cylinder 4 (internal short or damaged element); Damaged, chafed or corroded wiring or connector on the cylinder 4 glow plug circuit, shorted to voltage; Fault inside the glow plug control module or driver stage for cylinder 4; Water ingress or corrosion at the glow plug connector or module plug; Poor earth or supply voltage problem affecting the glow plug system; Outdated or faulty control unit software, where the manufacturer has documented it for the engine.

P067B

Cylinder 4 Glow Plug Control Circuit High.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
6: AreaComputer and output circuits
7B: FaultThe specific fault in that area

What it means

P067B is the generic code for a high condition in the glow plug control circuit for cylinder 4, on a diesel engine. The engine control unit or glow plug control module monitors the circuit for that cylinder and saw a voltage or feedback signal higher than expected, which points to a short to voltage or a fault in the driver. The exact circuit layout and how the fault is detected depend on the make, model and engine.

Symptoms

Glow plug warning light on or flashing
Engine management or check engine light on
Hard starting or extended cranking when cold
Rough running, misfire or white smoke on cold start
Slightly higher emissions or noisy idle until warm
Glow plug system may be disabled, so no pre-heat or after-glow

Possible causes

Faulty glow plug on cylinder 4 (internal short or damaged element)likely
Damaged, chafed or corroded wiring or connector on the cylinder 4 glow plug circuit, shorted to voltagelikely
Fault inside the glow plug control module or driver stage for cylinder 4possible
Water ingress or corrosion at the glow plug connector or module plugpossible
Poor earth or supply voltage problem affecting the glow plug systempossible
Outdated or faulty control unit software, where the manufacturer has documented it for the enginerare

How to diagnose

Read all stored and pending codes and the freeze frame data, noting engine temperature and battery voltage when the fault set, and look for other glow plug codes.
Check the battery condition and charging voltage, as low or unstable voltage can upset glow plug diagnostics.
Visually inspect the cylinder 4 glow plug wiring, connector and the control module plug for chafing, heat damage, corrosion and moisture.
Check the glow plug control module and its fuses and relays, following the manufacturer wiring diagram for your model.
With the circuit disconnected, test the cylinder 4 wire for a short to voltage and check for correct continuity and insulation.
Measure the resistance of the cylinder 4 glow plug and compare it with the other plugs and the manufacturer specification.
Use a scan tool with live data or actuator tests, where supported, to see whether the module commands and reports the cylinder 4 output correctly.
Check for any manufacturer software updates or technical bulletins for the engine, then clear the code and retest from cold.

How to fix

Replace the cylinder 4 glow plug if its resistance is out of specification or it is shorted, using the correct type for the engine.
Repair or replace damaged wiring and connectors on the cylinder 4 circuit, and fix the cause of the chafing or moisture entry.
Replace the glow plug control module if the driver for cylinder 4 is proven faulty.
Correct supply, fuse or earth faults found in the glow plug system.
Apply a manufacturer-approved software update if a known calibration fault matches the symptoms.

Can I keep driving?

Medium severity

The car can usually be driven short term, but cold starting may be poor and the fault should be fixed soon. Avoid repeated cold starts in cold weather, and stop if there is heavy smoke, severe misfire or the engine runs badly.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.