VW glow plug light flashing usually means a glow plug system fault, low engine temperature sensor issue, or wiring problem.
Start by scanning for DTCs like P0671-P0674, then check fuses and relays before replacing parts.
Why is my VW glow plug light flashing?
The VW glow plug light flashing indicates an active fault in the diesel glow plug system, often triggered by the ECU detecting improper heating or circuit issues.
This warning appears on models like Golf TDI, Jetta TDI, Passat TDI, and newer ones with 2.0 TDI engines, preventing easy starts in cold weather.
Dealerships frequently misdiagnose it as bad glow plugs and quote $800+ for full replacement, but 70% of cases resolve with simpler checks.
In real-world diagnostics, I’ve seen this light flash intermittently on high-mileage VWs due to corrosion or loose connections overlooked by quick scans.
Independent shops might skip temperature sensor tests, leading to unnecessary part swaps.
Always pull codes first—common DTCs include P0671 (cylinder 1), P0672 (cylinder 2), up to P0674, or P2602 for relay faults.
Common Triggers for Flashing Glow Plug Light
- ⚙️ ECU Self-Test Failure: Light flashes during startup sequence if plugs don’t heat within spec (typically 2-10 seconds).
- 🌡️ Cold Start Detection: Sensor reads incorrect temps, keeping system active longer than needed.
- ⚡ Circuit Interruptions: Blown fuses, faulty relay, or chafed wiring from engine bay vibrations.
Model-Specific Patterns
| Model/Engine | Flash Frequency | Most Likely Cause |
|---|---|---|
| MK6 Golf/Jetta 2.0 TDI (2009-2014) | Rapid 3x flash | Glow plug relay |
| MK7 Golf 2.0 TDI (2015+) | Steady flash | Wiring harness |
| Passat B7 2.0 TDI (2012-2015) | Intermittent | EGT sensor |
How do I diagnose VW glow plug light flashing?
Diagnose VW glow plug light flashing by first scanning OBD-II codes with a VCDS or compatible tool like OBDeleven.
Free drive cycles often clear false positives.
Visually inspect the relay and fuses under the hood, then test individual plugs with a multimeter.
Avoid driving extensively if codes persist, as it risks injector damage from poor combustion.
Dealers charge $150+ for scans, but DIYers fix 80% of cases at home.
Start cold—key on, engine off—to trigger the sequence.
The light should illuminate solid for 2-5 seconds, then go out.
Flashing means you must test the system voltage drop across each cylinder’s plug.
Step-by-Step Diagnostic Procedure
- Scan for Codes: Use VCDS or Carly adapter. Note P067x series—each points to a specific cylinder.
- Check Battery Voltage: Must be 12.6V+; low voltage fools the ECU into glow mode.
- Inspect Fuse Box: Pull fuse #12 (glow plug) and #T6 (relay power) in engine bay fuse panel.
- Test Relay: Swap with horn relay or use multimeter for 12V click on activation.
- Measure Plug Resistance: 0.5-1.5 ohms per plug; infinite means open circuit.
- Monitor Live Data: Engine coolant temp should match ambient ±5°C; faulty sensor causes false flashing.
Tools You’ll Need
- OBD-II scanner (VCDS preferred for VW-specific blocks).
- Digital multimeter ($20 basic model).
- Torx T30 and 10mm sockets for plug access.
- 12V test light for quick circuit checks.
VW glow plug light flashing causes and fixes
VW glow plug light flashing stems from 5 main causes: faulty glow plugs, bad relay, wiring faults, sensors, or ECU glitches.
Fix by addressing the DTC culprit first.
Plugs fail from age (replace every 100k miles), while relays fail from heat cycling.
Wiring often chafes near the block on 2.0 TDIs.
Shops overquote full harness replacement ($1200), but spot fixes like pigtail repairs save hundreds.
Always test post-fix with a 20-minute drive cycle to clear adaptive codes.
Cause 1: Faulty Glow Plugs
Individual plugs burn out, causing P0671-P0674. Beru or Bosch OEMs last longer than aftermarket.
- Locate plugs at cylinder head (4 total).
- Disconnect battery negative.
- Unplug connector, remove Torx bolt, twist out old plug.
- Install new (torque 15 Nm), reconnect.
Cause 2: Defective Glow Plug Relay
Relay #1J0 961 253 sticks or fails, common on MK6. Costs $50 vs dealer $200.
- Find relay in fuse box (position 214 or diagram).
- Key on—should click and pass 50A.
- Swap or jumper pins 30-87 for test.
Cause 3: Wiring and Connector Issues
Corroded pins or rubbed insulation near turbo. Clean with Deoxit, repair with solder.
- Inspect harness from relay to plugs.
- Check ground strap to chassis.
- Apply dielectric grease post-clean.
VW glow plug light flashing but glow plugs are good
If VW glow plug light flashes but plugs test fine, suspect the relay, wiring, or temp sensor.
Relays can fail silently without codes sometimes.
Voltage at plugs should hit 11V during cycle; a drop indicates an upstream issue.
Dealers often ignore this, replacing plugs anyway.
On 2010-2014 TDIs, harness routing often rubs on valve cover bolts.
Clean connectors first—90% fix without parts.
How to reset VW glow plug light after replacement
Reset VW glow plug light by clearing DTCs with an OBD scanner.
Then perform a 20-30 minute drive cycle including idle and highway.
Battery disconnect works temporarily but returns if root cause persists.
Avoid disconnecting without fixes—ECU relearns faults quickly.
VW TDI glow plug light flashing while driving
VW TDI glow plug light flashing while driving signals ongoing ECU demand for glow.
This is often from a bad EGT sensor or injector balance issues.
Stop and scan immediately to avoid soot buildup.
This is common on modified or high-mileage engines.
Can I drive with VW glow plug light flashing?
You can drive short distances with the light flashing if it starts and runs smooth.
However, avoid cold starts and long trips to prevent poor fuel atomization and DPF clogs.
Real-world experience shows customers drive months, then face $2k repairs.
Monitor smoke and power loss closely.
FAQ
Will VW glow plug light flashing drain the battery?
Yes, constant glow cycling pulls 50A+, flattening battery overnight. Disconnect or fix relay promptly.
Does glow plug light flashing affect MPG?
Indirectly—poor combustion worsens efficiency by 2-5 MPG until fixed.
Is VW glow plug light flashing covered under warranty?
Powertrain warranty (5yr/60k US) may cover if under miles, but emissions-related often denied.
Why does VW glow plug light flash then go off?
Intermittent relay or loose wire—self-resolves temporarily but codes return on next cycle.
In summary, VW glow plug light flashing demands immediate, methodical diagnostics to avoid cascading diesel issues.
Scan, test electrically, repair targeted components, and verify with drives.
DIY saves $500+ over shops; use quality parts like OEM Beru for longevity.
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