Faulty glow plug on cylinder 3 (most common); Damaged or corroded electrical connector at the glow plug; Open or shorted wiring in the glow plug circuit; Failed glow plug control module or relay; Poor ground connection for the glow plug circuit; ECM internal fault (rare)

DTC codes / P06xx · Computer and output circuits / P0673

P0673Cylinder 3 Glow Plug Circuit

Q: What does code P0673 mean?

Cylinder 3 Glow Plug Circuit. P0673 indicates that the engine control module (ECM) has detected an electrical fault in the glow plug circuit for cylinder 3. The ECM monitors the circuit for expected resistance and current draw; when the signal is out of range, it sets this code. This typically affects cold-start performance and may illuminate the check engine light.

P0673 indicates that the engine control module (ECM) has detected an electrical fault in the glow plug circuit for cylinder 3. The ECM monitors the circuit for expected resistance and current draw; when the signal is out of range, it sets this code. This typically affects cold-start performance and may illuminate the check engine light.

SystemPowertrain

Code typeGeneric (all makes)

SeverityLow

Fix difficultyIntermediate

AreaComputer and output circuits

Symptoms you may notice

Check engine light (malfunction indicator lamp) illuminated
Hard starting or rough idle when the engine is cold
Excessive white smoke from the exhaust after a cold start
Engine misfire or hesitation until warmed up
Often no symptoms besides the warning light, especially in mild climates

Common causes, most likely first

Faulty glow plug on cylinder 3 (most common)
Damaged or corroded electrical connector at the glow plug
Open or shorted wiring in the glow plug circuit
Failed glow plug control module or relay
Poor ground connection for the glow plug circuit
ECM internal fault (rare)

How to diagnose and fix it

Perform a visual inspection of the cylinder 3 glow plug, connector, and wiring for damage or corrosion
Check the glow plug resistance with a multimeter and compare to specification
Test the glow plug circuit for voltage and ground with the key on and engine cold
Inspect and test the glow plug control module and relay
Repair or replace damaged wiring or connectors as needed
Replace the faulty glow plug if resistance is out of range
Clear the code and verify the repair with a cold-start test

Glow plug circuit faults often misdiagnosed

A glow plug that tests fine when cold can still fail intermittently when hot, so resistance checks should be done at both temperatures.
Corroded connectors and chafed wiring are common causes that mimic a failed glow plug, so always inspect the harness before replacing parts.
The glow plug control module can fail in ways that affect only one cylinder, leading to unnecessary glow plug replacement.
P0673 can be set by a poor engine ground, which affects the entire glow plug system and may cause multiple glow plug codes.
In some vehicles, the glow plug circuit is energized after the engine starts for emissions purposes, so a fault may not cause noticeable driveability issues.

Can I keep driving with P0673?

You can generally continue driving with P0673, but cold starting may be rough and white smoke may be present. Avoid heavy loads or high speeds until the engine is warmed up, and address the issue promptly to prevent further electrical damage.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.