Failed glow plug on cylinder 1 (open-circuit heating element); Damaged, corroded or loose wiring or connector at the cylinder 1 glow plug; Corroded or loose glow plug terminal, supply feed or earth connection; Fault in the glow plug control module or relay output for cylinder 1 (on systems with individual drivers); Blown fuse or voltage supply problem to the glow plug system; Open circuit or short in the harness between the control module and the glow plug.

P0671

Cylinder 1 Glow Plug Circuit/Open.

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
71: FaultThe specific fault in that area

What it means

P0671 means the engine control unit has detected an open circuit or a fault in the glow plug circuit for cylinder 1 on a diesel engine. The control unit monitors the glow plug feed, driver or current draw, and the reading was outside the expected range, suggesting little or no current is flowing. The exact monitoring method varies by model and engine.

Symptoms

Hard starting or extended cranking on cold mornings
White smoke from the exhaust on a cold start
Rough or uneven running until the engine warms up
Glow plug warning lamp or engine management light on
Increased diesel knock when cold

Possible causes

Failed glow plug on cylinder 1 (open-circuit heating element)likely
Damaged, corroded or loose wiring or connector at the cylinder 1 glow pluglikely
Corroded or loose glow plug terminal, supply feed or earth connectionpossible
Fault in the glow plug control module or relay output for cylinder 1 (on systems with individual drivers)possible
Blown fuse or voltage supply problem to the glow plug systempossible
Open circuit or short in the harness between the control module and the glow plugrare

How to diagnose

Read all stored and pending codes and note the freeze frame data, including coolant temperature and battery voltage
Check for other glow plug codes, as several codes can point to a shared supply, fuse or module fault
Visually inspect the cylinder 1 glow plug connector, terminal and harness for heat damage, corrosion, chafing or looseness
Check the relevant fuses and relay, and test battery condition and charging voltage
Measure the glow plug resistance or current draw against the manufacturer's specification for that engine
Check for supply voltage and earth at the glow plug connector while the system is activated, following the model-specific procedure
Test the wiring between the glow plug control module and the plug for continuity and shorts
If wiring and plug are good, test the control module output as per the manufacturer's procedure

How to fix

Replace the faulty cylinder 1 glow plug, using the correct specification for the engine, and tighten to the specified torque
Repair or replace damaged wiring, terminals or connectors
Clean and secure corroded supply and earth connections
Replace blown fuses or a faulty relay after finding the cause of the failure
Replace the glow plug control module if testing confirms an output fault
Clear the code after repair and confirm it does not return

Can I keep driving?

Low severity

The car can usually be driven, but cold starting may be poor and emissions higher until it is repaired. Book it in soon, and take care when removing seized glow plugs as they can snap in the cylinder head.

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