P0672 Code: Cylinder 2 Glow Plug Circuit/Open
P0672: Compare the Cold Circuit
Prove the plug, lead and control channel before removing parts.
DIAGNOSTIC FOCUS
- FAULT TYPE
- Cylinder 2 glow-plug branch
- FIRST CHECKS
- Plug, connector, lead, module channel and shared supply
The fault identifies a cylinder-specific electrical branch; it does not prove the glow plug itself is open or that cylinder 2 has low compression.
P0672 means Cylinder 2 Glow Plug Circuit/Open. Older standardized lists may display Cylinder 2 Glow Plug Circuit without the /Open suffix, while current OEM displays can include it. Preserve the exact text shown by the vehicle.
Save the cold-start code set and battery context, confirm cylinder numbering and identify the cylinder 2 plug, lead and module channel. Compare the circuit under the OEM cold conditions before removing a glow plug that may be fragile or seized.
What Does the P0672 Code Mean?
The glow-plug controller or engine controller monitors the electrical behavior of the cylinder 2 glow-plug branch. Depending on the application, it may evaluate current, voltage or a modeled channel response during a cold preheat or post-heat phase.
Cylinder 2 must be identified from the engine's firing-order and service information. A bank, left/right assumption or harness position can lead to testing and replacing the wrong plug.
An open plug is one possibility, but a loose terminal, damaged lead, failed control-module channel, missing shared feed or ground, wrong plug or installation damage can create the same code. Cold-start smoke or roughness also requires separate fuel, compression and engine evidence.
Record coolant/ambient context, battery state and whether the module commanded a preheat or post-heat event.
Compare the cylinder 2 branch with known-good branches only according to the OEM method and connector mapping.
Electrical proof should precede removal because a seized, side-loaded or overtightened glow plug can break or damage the engine.
P0672 Symptoms, Severity, and Driving Safety
Save both warning states and all cylinder-specific or module codes. Several cylinder codes can identify a shared feed or controller issue.
One inactive glow plug may extend cranking in cold conditions, especially when other preheat or battery concerns are present.
Cylinder 2 may contribute late during a cold start, but fuel delivery, compression and injector faults can produce similar behavior.
Incomplete cold combustion can create smoke. The code alone does not prove the glow plug caused all smoke or that driving will clear it.
Low cranking voltage and a glow fault can compound one another. Record battery and starter context without assigning a universal voltage threshold.
The engine may restart normally when warm because glow assistance is reduced. That pattern supports cold-context testing but does not identify the failed component.
Prompt diagnosis helps prevent repeated cold-start stress and unburned-fuel smoke. Stop for severe smoke, fuel accumulation, overheating, a no-start in an unsafe location or damaged high-current wiring.
P0672 Causes: Glow Plug, Lead, Module Channel, or Shared Supply?
These six branches separate the cylinder 2 plug from its lead, controller channel and conditions shared with other cylinders.
Open or Incorrect Cylinder 2 Glow Plug
The heating element can become open, or an incorrect plug can have electrical behavior the controller does not expect.
How to prove it: Confirm cylinder location and compare the plug with the OEM component test before removal or replacement.
Check firstLoose, Corroded, or Damaged Plug Connector
A poor terminal at the plug can interrupt a high-current branch and may be sensitive to vibration or temperature.
How to prove it: Inspect terminal retention, heat damage and corrosion without side-loading the plug terminal.
Check firstOpen or High-Resistance Cylinder Lead
Harness damage, a weak splice or internal lead fault can reduce current even when the plug itself is serviceable.
How to prove it: Isolate the lead and compare voltage drop or current by the protected OEM method.
Verify directlyGlow Control Module Channel Fault
The individual cylinder 2 driver can fail or may be integrated into a nonserviceable controller assembly.
How to prove it: Prove shared supply/ground and the plug/lead before condemning a channel or module.
Verify directlyShared Feed, Ground, Relay, or System Condition
A loose ground, weak supply or application-specific relay concern can set several glow-related codes, including P0672.
How to prove it: Review the complete code pattern and load-test shared paths. Apply relay bulletins only to their listed applications.
Verify directlyInstallation Damage or Wrong Procedure
Side load, excessive torque, contamination or wrong part geometry can crack a ceramic element or damage threads and terminals.
How to prove it: Use the exact part, preparation, torque and removal procedure; stop if extraction force or breakage risk exceeds guidance.
Final branchTest temperature and controller strategy matter. Glow-plug resistance and current vary with plug type and temperature, so no universal value should be inserted into the article.
Using UR800 to Diagnose P0672
The iCARZONE UR800 Full-System Bidirectional Scan Tool with ECU Coding supports full-system diagnostics, available DTCs, freeze frame, ECU information and live data. Save P0672 status, coolant/ambient context, system voltage, glow command/channel data and every cylinder or module code. Where supported, compare commanded glow status and cylinder current information before disturbing the harness.
The official product page advertises bidirectional control and ECU coding. Coverage varies by VIN, ECU and software. Glow-plug PIDs and active tests vary by engine and module. A command or current estimate cannot independently prove plug resistance, lead voltage drop, terminal condition or cylinder compression.
Use the OEM cold test, protected high-current procedure and exact cylinder connector mapping. The scanner cannot measure physical plug resistance, lead continuity, terminal fit or compression, and it cannot make a seized plug safe to remove.
iCARZONE UR800 Full-System Bidirectional Scan Tool with ECU Coding
Save the cold-start report and compare supported glow-channel data before disconnecting the cylinder 2 lead.
Price and availability checked September 1, 2026. Prices shown are USD. Recheck the current offer, stock and required vehicle/function coverage before purchase.
How to Diagnose P0672 Before Removing the Cylinder 2 Glow Plug
Preserve the cold event and confirm cylinder numbering. Compare the cylinder 2 plug branch with shared module conditions and other cylinders, then plan removal only if the electrical evidence supports it.
P0672 Quick Diagnostic Path
-
1
Save the Complete Cold-Start Event
- Record P0672 status, suffixes, freeze frame, coolant/ambient context, battery condition and all glow-module or cylinder-specific codes.
- Note cranking time, smoke, roughness and whether the engine was truly cold. Do not clear a multi-cylinder pattern before checking shared conditions.
-
2
Confirm Cylinder 2 and the Controller Channel
- Use engine-specific firing-order, component-location and connector information to identify the cylinder 2 plug, lead and module terminal.
- Do not assume cylinder numbering from vehicle left/right orientation. Confirm whether the controller and internal harness are separately serviceable.
-
3
Inspect the Plug Terminal, Lead, Feed and Grounds
- With the engine cool and circuit safely disabled, inspect terminal retention, corrosion, rubbing, heat damage, shared connectors and documented grounds.
- Do not bend or side-load a ceramic plug terminal. Preserve evidence of incorrect installation or water entry.
-
4
Compare the Cold Electrical Branches
- Follow the OEM procedure to compare cylinder 2 current, voltage drop, resistance or channel response with specified conditions and suitable cylinders.
- Use protected equipment for high-current circuits. Do not apply battery power directly or use a universal resistance threshold.
-
5
Separate Plug, Lead and Module Channel
- Isolate the component only as directed to determine whether the abnormal result follows the plug, remains in the lead or originates at the controller channel/shared supply.
- If electrical results pass but rough cold operation remains, continue fuel, injector and compression diagnosis rather than forcing a glow-plug conclusion.
-
6
Repair Carefully and Verify on a True Cold Start
- Repair the proven connector, lead, plug, module/shared condition or scoped relay issue. Use exact preparation, torque and setup procedures.
- Verify the channel through the required preheat/post-heat event and a true cold start, then recheck smoke, running quality and returning codes.
How to Fix P0672 and Verify the Repair
Repair the Cylinder 2 Connector or Lead
Restore the proven terminal, sealed wire or internal-lead fault and verify loaded operation without side-loading the plug.
Replace a Proven Glow Plug Correctly
Use the exact plug and OEM cool-engine removal, preparation and torque process. Do not replace it solely from the code.
Correct Module Channel or Shared Supply/Ground
Repair the demonstrated controller, feed, relay, splice or ground problem and recheck all cylinder channels.
Apply a Matching Relay or Control Procedure
Use a bulletin or setup action only when the exact vehicle, code pattern and hardware match current OEM information.
Cold-System Scan and Branch Comparison
VIN-specific quoteComplete code set, battery context, cylinder mapping and controlled current/circuit tests.
Accessible Glow Plug Service
VIN-specific quotePart, access, thread condition and careful installation when removal is straightforward.
Harness or Glow-Module Repair
VIN-specific quoteConnector access, internal lead design, shared feed/ground and required setup.
Difficult Removal or Extraction
VIN-specific quoteSeized/broken plug risk, specialist tooling, cylinder-head access and post-repair verification.
Ask for an estimate that separates electrical diagnosis from plug removal. A cheap open lead and a seized glow plug can have very different risk and labor even with the same code.
Verify after a true cold soak under conditions that request glow operation. A warm restart, code clear or brief smooth idle does not prove the cylinder channel is restored.
P0672 OEM Differences and DIY Limits
Ford's diesel OBD monitor summary lists P0672 as Cylinder 2 Glow Plug Circuit and describes a continuous current-monitor strategy under specified conditions. The listed currents and enabling logic are Ford-application examples, not universal specifications.
An OEM controller can judge a cylinder branch by its current behavior during a commanded glow phase.
Several glow or module codes together can point to a shared ground instead of several failed plugs.
Side load and incorrect torque can damage ceramic plugs, so electrical proof should precede removal.
GM bulletin 23-NA-164 includes P0672 in a multi-code pattern associated with a loose, damaged or dirty ground on specified vehicles. GM service information also warns that side-loading or overtightening a ceramic glow plug can crack it during installation.
- Save all glow and cylinder codes before clearing.
- Record cold-start temperature, cranking, smoke and battery context.
- Confirm cylinder 2 from reliable engine information.
- Inspect an accessible cool connector without pulling sideways on the plug.
- Perform protected high-current and module-channel tests.
- Measure the plug and lead by the OEM cold method.
- Remove a seized or fragile glow plug safely.
- Diagnose compression/fuel causes and verify a true cold-start cycle.
Frequently Asked Questions About P0672
What does P0672 mean?
Does P0672 prove the glow plug is bad?
Where is cylinder 2?
Should all glow plugs be replaced together?
Can a weak battery cause or worsen the symptoms?
Can I drive with P0672?
Can UR800 test glow plugs?
How do I verify a P0672 repair?
Sources and Technical Review Notes
- Ford 2007 Diesel OBD System Operation Summary — Lists P0672 as Cylinder 2 Glow Plug Circuit and shows one Ford strategy monitors individual glow-plug current continuously under defined conditions.
- GM Bulletin 23-NA-102: Ground Connection Inspection — Lists P0672 among DTCs that may occur with a loose/damaged/dirty ground on specified vehicles, so the plug alone is not proven.
- GM Bulletin 23-NA-032: Glow Plug Installation Information — Warns that side loading or overtightening a glow plug can crack its ceramic and cause premature failure.
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