Faulty cylinder 4 glow plug with internal short or abnormal resistance; Wiring to the cylinder 4 glow plug chafed or shorted to earth; Corroded, loose or damaged connector or terminal at the glow plug or control module; Carbon or moisture tracking at the glow plug terminal or a damaged harness boot; Faulty glow plug control module or driver channel for cylinder 4; Low supply voltage or poor earth affecting the glow plug circuit; Outdated or faulty control unit software, where the manufacturer has issued a known update.

P067A

Cylinder 4 Glow Plug Control Circuit Low.

Generic
Powertrain
Generic code
Low severity

How this code is built

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

What it means

P067A is the generic code for a low signal in the cylinder 4 glow plug control circuit on a diesel engine. The engine control unit (or glow plug control module) monitors the circuit that feeds or switches the cylinder 4 glow plug and has seen a voltage or current lower than expected. This usually points to a short to earth, high resistance or a failed glow plug or driver. How the circuit is arranged and monitored depends on the model and engine.

Symptoms

Glow plug warning light on or flashing
Engine management or check engine light on
Hard starting in cold weather
Rough running or white smoke on a cold start
Slightly higher emissions or noisy idle until warm
Car may enter a reduced-performance mode on some models

Possible causes

Faulty cylinder 4 glow plug with internal short or abnormal resistancelikely
Wiring to the cylinder 4 glow plug chafed or shorted to earthlikely
Corroded, loose or damaged connector or terminal at the glow plug or control modulelikely
Carbon or moisture tracking at the glow plug terminal or a damaged harness bootpossible
Faulty glow plug control module or driver channel for cylinder 4possible
Low supply voltage or poor earth affecting the glow plug circuitpossible
Outdated or faulty control unit software, where the manufacturer has issued a known updaterare

How to diagnose

Read all stored and pending codes and note freeze frame data, including battery voltage and coolant temperature, then check for other glow plug codes.
Check battery condition and charging voltage, as low voltage can upset glow plug diagnostics.
Visually inspect the cylinder 4 glow plug connector, harness and boot for chafing, heat damage, corrosion, moisture or oil contamination.
Check the glow plug fuses and relevant power feeds and earths, following the wiring diagram for the specific model and engine.
Measure the cylinder 4 glow plug resistance and compare it with the manufacturer specification, and compare it with the other cylinders.
With the plug disconnected, check the control wire for a short to earth and for continuity back to the control module.
Use a scan tool with live data or an actuator test, where supported, to see whether the module drives cylinder 4 and check current draw.
If wiring and the plug are good, check for applicable software updates and test or replace the control module as the manufacturer advises.

How to fix

Replace the faulty cylinder 4 glow plug, using the correct specification and torque, and consider replacing the set if they are old.
Repair or replace damaged wiring between the control module and the cylinder 4 glow plug.
Clean or replace corroded or damaged connectors and terminals and refit weather seals.
Correct battery, supply or earth faults found during testing.
Replace the glow plug control module if it is confirmed faulty, and code it to the vehicle if required.
Apply a manufacturer software update only if a calibration fault is a documented cause for the vehicle.

Can I keep driving?

Low severity

The car can usually be driven, but cold starting may be poor and emissions may be higher until it is fixed. Book it in soon, and stop if the engine runs very roughly or loses power.

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