P0687Mazda Cx-9Years: 1996 - 2026
Glow Plug Module / Supply Voltage (P0687)
Reviewed by ASE Certified Technician
What does this mean?
Code P0687 indicates a problem with the glow plug module control circuit or supply voltage (diesel engines).
Disclaimer: This diagnostic code is part of the standard OBD2 system and can apply to Mazda Cx-9 models manufactured from 1996 to 2026. However, please note that the presence of this specific code depends on your vehicle's exact engine configuration, options, and production year.
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Common Causes
Failed glow plug or glow plug module (diesel)
Damaged, chafed, or broken wiring harness
Corroded or loose electrical connector
Internal PCM/ECM failure
Weak or failing battery
Symptoms to Watch For
- Check Engine Light is illuminated
- Diesel engine hard to start in cold weather
- Glow plug indicator light stays on (diesel)
- White or blue smoke from exhaust
- Rough or unstable idle