P0674 Cylinder 4 Glow Plug Circuit

P0674 points to a cylinder 4 glow plug circuit problem. The controller detected an abnormal electrical response from the cylinder 4 glow plug path.

Code details

Generic OBD-II · P0

System: Computer
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not replace the glow plug module until the cylinder 4 plug and branch wiring have been isolated.

Symptoms of P0674

Check-engine light, sometimes with several unrelated codes at once.
Warning lights, a no-start, or intermittent electrical faults.
Communication or module-reset problems on a scan tool.

Common causes of P0674

Low battery voltage, poor grounds, corroded connectors, or blown fuses.
Wiring or network (CAN bus) faults between modules.
A module software/programming issue, or rarely a failed controller.

Useful checks before replacing parts

Check cylinder 4 glow plug resistance, control module output, command voltage, current draw, battery voltage, and freeze-frame temperature conditions.
Inspect the cylinder 4 harness lead, connector corrosion, terminal tension, heat damage, module connector pins, and possible open or short faults.
Compare cylinder 4 current ramp and resistance with known good cylinders to confirm whether the fault follows the plug or the circuit.

Related OBD-II codes

These nearby computer entries can help compare wording and pin down the fault area.