P0673
Cylinder 3 Glow Plug Circuit
The appearance of the standard OBD2 trouble fault code P0673 is an indicator that your vehicle ECU triggered a threshold alert for "Cylinder 3 Glow Plug Circuit". Understanding the root component breakdown helps avoid expensive diagnostic fees.
Driver's Summary
Your vehicle's computer logged P0673 after detecting a malfunction in the cylinder 3 glow plug circuit system. Typical symptoms include check engine light, sluggish cold starts. This code won't leave you stranded, but it indicates a real issue that will only get easier and cheaper to fix sooner rather than later.
Symptoms
Check engine light, sluggish cold starts
Common Causes
- Burnt out glow plug on cylinder 3
- Corrosion on glow plug harness
- Faulty glow plug control unit
- Soot buildup preventing good contact
How to Fix
- 1 Replace cylinder 3 glow plug
- 2 Clean and re-seat wiring harness
- 3 Check glow plug control module
- 4 Clean glow plug bore
Technical Explanation
Code P0673 is confirmed when the ECM's diagnostic algorithm detects a parameter deviation that persists across a defined number of consecutive drive cycles. The PCM distinguishes between electrical faults (circuit codes) and performance faults (rationality codes) by comparing the sensor's reported value against what other sensors would predict under the same engine operating conditions. The fault remains stored in memory even after the MIL is cleared; it becomes a confirmed DTC after failing two consecutive drive cycles, and the PCM logs a freeze frame record of the engine's exact operating state at the moment of detection.
Is It Safe to Drive?
Immediate safety risk is low with P0673 active. The primary concern is regulatory — this fault will cause a failed emissions test — and the secondary risk is that the small root cause (burnt out glow plug on cylinder 3) becomes a larger problem if ignored for months.
Mechanic's Pro Tip
Before replacing any component on P0673, spend 5 minutes inspecting the wiring harness and connector first — corrosion, chafed insulation, and backed-out pins cause the majority of these faults and cost nothing to fix. Use a multimeter to measure voltage drop across the connector pins under load; anything above 0.1V indicates excessive resistance that will cause intermittent failures even after replacing the sensor.
Glow plug and labor: $100 - $300