// Brand-Specific Diagnostics
Mercury Fault Codes
Complete reference guide for interpreting Mercury outboard numeric patterns and alarms.
How to Read Mercury Codes
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← Try the Interactive Code Decoder Numeric codes displayed on SmartCraft screens or heard via beep counts. Enter the number you see or hear.
Mercury Code Master List (11 Codes)
| Code | Fault Description | Severity | Required Action |
|---|---|---|---|
| 1 | Cam Sensor / High Voltage | HIGH | Check battery voltage and cam sensor circuit. |
| 2 | Low Battery Voltage | MEDIUM | Check battery charge and charging system. |
| 3 | Critical Overheat (Beeps) | CRITICAL | STOP ENGINE. Cooling system failure detected. |
| 4 | Engine Overheat (ECT) | CRITICAL | Check water pump and thermostat. |
| 13 | Low Oil Pressure | CRITICAL | STOP ENGINE. Check oil level immediately. |
| 16 | MAT (Air Temp) Sensor | LOW | Check manifold air temp sensor. |
| 23 | Low Sea Pump Pressure | HIGH | Check water intake and impeller condition. |
| 31 | TPS Circuit Fault | MEDIUM | Check throttle position sensor wiring. |
| 36 | 5V Reference Low | HIGH | Internal sensor power failure. Check wiring harness. |
| 94 | Pitot Circuit (Speedo) | INFO | Check speedometer sensor tube for clogs. |
| continuous | Guardian Mode Active | CRITICAL | STOP ENGINE. Protection mode activated. |
Troubleshooting Mercury Outboards
When your Mercury outboard triggers an alarm or flashing sequence, it means the Electronic Control Unit (ECU) has detected a reading outside of safe operating parameters.
Always prioritize CRITICAL severity codes. If you receive a critical code, such as low oil pressure or critical overheat, you should shut down the engine immediately to prevent catastrophic powerhead failure. HIGH priority codes usually trigger the engine's Guardian (Limp) Mode to restrict RPMs so you can safely return to the dock.