Faulty cylinder 7 glow plug (internal short or failed element); Wiring to the cylinder 7 glow plug chafed or shorted to earth; Corroded, loose or damaged connector or terminal at the glow plug or control module; Carbon tracking or moisture at the glow plug terminal or power rail causing a leak to earth; Fault in the glow plug control module output stage for cylinder 7; Faulty engine control unit driver circuit.

P068C

Cylinder 7 Glow Plug Control Circuit Low.

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
8C: FaultThe specific fault in that area

What it means

P068C means the engine control unit or glow plug control module has detected a low voltage or short-to-ground condition in the control circuit for the cylinder 7 glow plug. It sets when the monitored circuit voltage or current is lower than expected while the glow plug is commanded on or off. The code only applies to diesel engines with at least seven cylinders, and how the glow plugs are driven and monitored depends on the model and engine.

Symptoms

Hard starting or extended cranking in cold weather
White smoke or rough running on a cold start
Glow plug warning lamp or engine warning lamp lit
Slight misfire or uneven idle until the engine warms up
Increased emissions or noise on cold start

Possible causes

Faulty cylinder 7 glow plug (internal short or failed element)likely
Wiring to the cylinder 7 glow plug chafed or shorted to earthlikely
Corroded, loose or damaged connector or terminal at the glow plug or control modulepossible
Carbon tracking or moisture at the glow plug terminal or power rail causing a leak to earthpossible
Fault in the glow plug control module output stage for cylinder 7possible
Faulty engine control unit driver circuitrare

How to diagnose

Read all stored and pending codes and the freeze frame data, noting engine temperature, battery voltage and whether other glow plug codes are present
Check the battery condition and charging voltage, as low supply voltage can upset glow plug circuit monitoring
Visually inspect the cylinder 7 glow plug wiring, terminal and connectors for chafing, heat damage, corrosion and water ingress
Check the relevant fuses and relays against the manufacturer's wiring diagram
Measure the cylinder 7 glow plug resistance and current draw and compare with the specification for that engine
With the module connector disconnected, test the cylinder 7 control wire for a short to earth and for continuity end to end
Use live data or an output test, where supported, to see whether the module drives the cylinder 7 circuit correctly
Check the module and engine control unit for any applicable technical bulletins or software updates for this engine

How to fix

Replace the cylinder 7 glow plug if it is shorted or outside specification, following the correct torque and removal procedure
Repair or replace damaged wiring that is shorted to earth
Clean, repair or replace corroded or damaged connectors and terminals
Dry and clean the glow plug terminal area and replace any damaged seals or boots
Replace the glow plug control module if its output for cylinder 7 is confirmed faulty
Update the control unit calibration only where the manufacturer lists an outdated calibration as a known cause

Can I keep driving?

Medium severity

The car can usually be driven short term, but cold starting may become difficult and a shorted circuit could overload the module. Get it checked soon, and stop driving if you notice burning smells, repeated blown fuses or a serious misfire.

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