P0672 Code: Glow Plug Circuit Cylinder 2 – Diesel Fix Guide – iCarsoft Official Store

P0672: Glow Plug Circuit — Cylinder 2

ACTIVE DTC GUIDE · P0672 · Diesel / Glow Plug System

⚡ Quick Reference — P0672

DTC CodeP0672

DefinitionGlow Plug Circuit — Cylinder 2

SeverityHIGH — Hard Cold Starts, White Smoke

SystemDiesel Glow Plug / Glow Plug Control Module

Typical Repair Cost$60 – $450

Diagnostic ToolOBD-II + GPCM module access

1What Does P0672 Mean?

P0672 indicates the Glow Plug Control Module (GPCM) or ECM has detected a fault in the glow plug circuit for Cylinder 2. Diesel glow plugs are resistive heating elements that pre-heat the combustion chamber to enable cold starting without gasoline-like spark ignition. Each plug draws approximately 10–15 A during the pre-glow phase (typically 2–6 seconds before cranking) and 5–8 A during the post-glow phase. The GPCM monitors current draw for each cylinder individually — a plug that draws no current (open circuit) or excessive current (internal short at <0.5 Ω) triggers the individual cylinder code. A single failed plug noticeably increases cold start time and produces white exhaust smoke from the affected cylinder during warm-up.

Diesel engine cylinder 2 glow plug removal showing carbon deposits on tip and glow plug control module wiring harness

Fig 1. Cylinder 2 glow plug — carbon buildup on the tip is normal but inspect for cracks or swelling that indicate overtemperature failure.

2Most Affected Vehicles

Ford F-250/350 (6.0L / 6.4L Power Stroke)2003–2007 F-250/350 6.0L PS
2008–2010 F-250/350 6.4L PS
Glow plug failure from EGR-related overtemperatureEXTREMELY HIGH INCIDENCE

BMW 3/5 Series (M57 / N57 Diesel)2008–2013 BMW 335d M57 3.0 diesel
2012–2016 BMW 535d N57 3.0 diesel
Ceramic-tip glow plug failure at high mileageHIGH INCIDENCE

VW Passat / Golf TDI (2.0 TDI)2009–2014 VW Passat 2.0 TDI
2010–2014 Golf TDI — CJAA engine
Glow plug seizing in head at 100,000+ miMODERATE–HIGH

3Root Causes

Failed Glow Plug (Open Circuit)Internal heater coil breaks — plug draws zero current. Most common failure mode. Confirm with resistance test: 0.5–2.0 Ω is normal; OL (open) confirms failure.
Failed Glow Plug (Short Circuit)Internal short causes the plug to draw excessive current, triggering overcurrent protection in the GPCM. Less common but causes rapid GPCM failure if not corrected quickly.
Corroded or Damaged WiringHigh-current glow plug wiring (typically 10–12 AWG) corrodes at the plug terminal or GPCM connector. Voltage drop >0.5 V under load causes insufficient heating and GPCM fault logging.
Failed Glow Plug Control ModuleGPCM internal driver failure for cylinder 2 channel. Confirm by measuring correct voltage and current at the plug connector with GPCM commanding glow — if voltage is present but plug doesn't heat, it's the plug. If voltage is absent, it's the GPCM.

4Technical Specifications

📊 Cylinder 2 Glow Plug Circuit Reference

Glow plug resistance (normal, cold)0.5 – 2.0 Ω

Pre-glow current draw per plug10 – 15 A

Post-glow current draw per plug5 – 8 A

Glow plug supply voltage (pre-glow)11.5 – 14.5 V

Tip temperature at full pre-glow850 – 1,000 °C

P0672 open-circuit trigger (current)< 1 A when commanded on

Voltage drop trigger (harness fault)> 0.5 V under pre-glow load

⚡ EXPERT TIP — Never Dry-Remove on a Hot Engine

On VW TDI and BMW diesel engines, glow plugs seized in the cylinder head are the single most common outcome of P0672 neglect. If a plug has been in service over 80,000 miles or 6 years, soak the plug base with penetrating oil for a minimum of 4 hours on a warm (not hot) engine before removal. Remove plugs using an impact wrench in short bursts — never continuous torque. A broken plug tip in the combustion chamber requires head removal to extract and costs 10–20x the cost of a proper removal procedure.

5Diagnostic Steps

1

GPCM Module ScanUse iCarsoft CR Ultra P to access the Glow Plug Control Module directly. Confirm P0672 is a single-cylinder fault. Multiple cylinder codes (P0671–P0678) indicate GPCM failure or a main supply fuse issue.
2

Measure Glow Plug ResistanceDisconnect the cylinder 2 glow plug wire. Measure resistance between the plug terminal and engine ground. 0.5–2.0 Ω = functional. OL = open/failed. <0.3 Ω = shorted.
3

Verify GPCM Output VoltageWith GPCM commanding pre-glow (key on, don't start), measure voltage at the cylinder 2 glow plug connector. Should read battery voltage. Low or no voltage points to GPCM output failure or wiring fault.
4

Replace Plug Using Correct ProcedureSoak, warm engine, remove with care. Install OEM or NGK/Bosch equivalent plug. Torque to specification (typically 10–15 Nm — never over-torque). Apply anti-seize to threads.
5

Clear & Cold-Start VerifyClear codes with iCarsoft CR Ultra P. Monitor GPCM live data during cold start: verify cylinder 2 current reaches 10+ A during pre-glow. Confirm no white smoke and smooth cold start idle.

Recommended Diagnostic Tool iCarsoft CR Ultra P Direct GPCM module access with per-cylinder glow plug current monitoring — the only way to accurately diagnose P0672 vs. GPCM failure on Ford Power Stroke, BMW diesel, and VW TDI platforms.