P0671 Cylinder 1 Glow Plug Circuit

P0671 indicates a cylinder 1 glow plug circuit fault. The controller sees an electrical problem in the glow plug circuit for cylinder 1.

Code status

Needs verification

Not yet verified against SAE J2012_202509 / J2012DA. Treat unverified rows as a lookup aid, not repair authority.

System: Computer
Scope: iso-sae-controlled-p0
Standard: SAE J2012 / ISO 15031-6
Source: legacy-import

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 multiple glow plugs without comparing cylinder 1 measurements against the remaining cylinders.

Useful checks before replacing parts

Check cylinder 1 glow plug resistance, command voltage, current draw, connector condition, battery voltage, coolant temperature, and freeze-frame data.
Inspect the cylinder 1 glow plug lead, terminal tightness, module output, harness heat damage, corrosion, and shorts to ground or power.
Compare cylinder 1 current and resistance against known good cylinders to separate a failed plug from wiring or module output faults.

Related OBD-II codes

These nearby computer entries can help compare wording and fault area. They may share the same verification status as the source database.