MerCruiser fault codes are diagnostic codes that apply to given malfunctions. These codes can be pulled in many ways including using a diagnostic tool or decoding the flashing pattern of the check engine light.
If you want to find out more about the topic and read the official MerCruiser DTC list, you’ve come to the right place.
We at PowerSportsGuide have compiled all you need to know under one roof!
What are Fault Codes on a MerCruiser?
Just like many vehicles and vessels, most MerCruiser engines also feature an onboard computer (ECU), which is considered the ‘brain’ of the motor.
In case of a malfunction, this main computer generates a code that describes a particular malfunction.
MerCruiser fault codes are known by many names including service codes, error codes, and diagnostic trouble codes (DTCs).
How do You Read Fault Codes on a MerCruiser?
In a nutshell, the five easiest ways to read the fault codes on a MerCruiser are as follows:
- VesselView mobile app
- Digital display/gauge
- Voltage tester
- Use a diagnostic scanner tool
- Take the motor to a dealership or service shop
Let’s take a close look at each!
1. VesselView Mobile App
It’s safe to say that the easiest way to check fault codes and error messages on a MerCuriser motor is by using the VesselView Mobile kit.
This innovative feature is a device designed to connect your smartphone or tablet to a Mercuriser engine via Bluetooth.
The kit comes with all the required hardware and the downloadable VesselView Mobile app.
The latter allows you to read a lot of useful information from the motor, including live engine data, maintenance reminders, fuel management, and even fault codes.
It’s as easy as it sounds!
2. Digital Display/Gauge
To the greatest regret of many fans, older MerCruiser motors are not compatible with the VesselView mobile kit.
However, they can still be paired with digital displays and gauges, like the SmartCraft gauge system with a simple SC100/SC1000.
These gauges are designed to display a lot of useful engine data, and error messages and codes are no exception. They can use pictograms, texts, or both for describing the present malfunction.
However, they typically only display the “soft” alarms, which are triggered by simpler issues.
But if your motor has a serious malfunction, you will likely have to dig deeper and pull the fault codes (DTC codes) from the engine or even run a complete diagnostic.
Let’s see how you can do it!
3. Voltage Tester
If you have an older MerCruiser with a MEFi3 system, you can pull the fault codes from it with a simple paperclip and a regular tester.
Here’s a great tutorial on how you can do it:
Once you’ve pulled the code all you need to do is decode it with the help of this chart:
MerCruiser Marine EFI Trouble Codes
| GM Marine EFI Systems Trouble Code Chart | |||
| # | Indicator Light Flash Sequence | Description | MEFI |
| 12 | One flash, pause, two flashes | Self Diagnostic System Functioning Properly | 1,2 & 3 |
| 14 | One flash, pause, four flashes | Coolant Temperature Sensor (CTS) Low Temp | 1,2 & 3 |
| 15 | One flash, pause, five flashes | Coolant Temperature Sensor (CTS) High Temp | 2 & 3 |
| 21 | Two flashes, pause, one flash | Throttle Position Sensor (TPS) Signal Voltage High | 1,2 & 3 |
| 22 | Two flashes, pause, two flashes | Throttle Position Sensor (TPS) Signal Voltage Low | 2 & 3 |
| 23 | Two flashes, pause, three flashes | Manifold Air Temperature Sensor (MAT) Low Temp | 3 only |
| 25 | Two flashes, pause, five flashes | Manifold Air Temperature Sensor (MAT) High Temp | 3 only |
| 33 | Three flashes, pause, three flashes | Manifold Absolute Pressure (MAP) Signal Voltage High | 1,2 & 3 |
| 34 | Three flashes, pause, four flashes | Manifold Absolute Pressure (MAP) Signal Voltage Low | 2 & 3 |
| 41 | Four flashes, pause, one flash | Ignition Control Circuit (IC) Open IC Circuit | 2 & 3 |
| 42 | Four flashes, pause, two flashes | Ignition Control Circuit (IC) Grounded or Open Bypass | 1,2 & 3 |
| 43 | Four flashes, pause, three flashes | Knock Sensor (KS) Continuous Knock Detected | 1,2 & 3 |
| 44 | Four flashes, pause, four flashes | Knock Sensor (KS) No Knock Detected | 2 & 3 |
| 45 | Four flashes, pause, five flashes | Coil Driver Fault | 3 only |
| 51 | Five flashes, pause, one flash | ECM Calibration Memory Failure | 1,2 & 3 |
| 61 | Six flashes, pause, one flash | Fuel Pressure High | 3 only |
| 62 | Six flashes, pause, two flashes | Fuel Pressure Low | 3 only |
Disclaimer: This list is for informational purposes only and is not necessarily applicable to any model. For more information, please check the official service manual.
4. MerCruiser Diagnostic Scanner
If you want to dig deeper, you will need a scanner tool to pull the codes and run a complete engine diagnostic.
Thanks to their popularity, MerCruiser engines are compatible with most major diagnostic scanner devices.
Without the need for completeness, the most well-known MerCruiser diagnostic scanners are as follows:
- MerCruiser Digital Diagnostic Terminal
- TechMate Pro from Rinda Technologies
- MEDS Marine Diagnostics
- Diacom Diagnostic Tool and Software
- CanDooPro
Before making your purchase, make sure that the chosen scanner is compatible with your motor. Compatibility may depend on the make and model.
These devices are designed to attach the diagnostic port of the motor to a laptop via a special diagnostic cable. They also come with software that has to be installed on your laptop.
Designed to communicate directly with the ECM, a diagnostic scanner like a MEDS Marie diagnostic can provide a lot of useful information, including:
- Hands-free information
- Engine configuration data
- Displays active & inactive faults
- Clear faults with a single click
- Displays run history by RPM range and # of hours
- Set / Monitor Break-In Period
- Display engine functions during a fault (i.e. an engine stall)
- Drill down to the engine failure (i.e. injector)
- Individually test components (i.e. one injector at a time)
5. Take Your Boat to a Dealer
If you can’t read the error code on your MerCruiser engine for some reason, your last option is to take the boat to a reputable shop or authorized dealership.
Although this involves some hassle, a professional can not only read the code for you but can also help with repairs.
MerCruiser Fault Code List
For your convenience, we’ve listed the official MerCruiser fault codes:
| Alarm | # | Fault | Pwr Limit | Description | |
| Constant horn | 4 | ECT Coolant Overheat | 6-100% | Overheat condition detected by Engine Coolant Temp (ECT) circuit. | |
| 13 | Low Oil Pressure Strategy | 0-100% | Low oil pressure strategy. Stop immediately and check engine oil. | ||
| 19 | Overspeed | RPM Limit | Engine over RPM limit | ||
| 22 | Port EMCT CKT Overheat | 6-100% | Overheat in port Exhaust Manifold Coolant Temp (EMCT), 212°F (100°C) limit | ||
| 23 | Sea Pump PSI Lo | 6-100% | Low water pressure strategy, defaults to 43.4 psi. | ||
| 28 | STB EMCT CKT Overheat | 6-100% | Overheat in stbd Exhaust Manifold Coolant Temp (EMCT), 212°F (100°C) limit | ||
| Steady beeps | 12 | Low Drive Lube Strategy | 0-100% | Low oil in sterndrive. Stop immediately and check drive lube bottle. | |
| 2 beeps once per minute | 1 | Cam Sensor | 90% | Open or short in cam sensor. Engine must be cranking to set this code. | |
| 2 | ECT CKT HI | 90% | Open in Engine Coolant Temp (ECT) circuit | ||
| 3 | ECT CKT LO | 90% | Short in Engine Coolant Temp (ECT) circuit | ||
| 5 | EST 1-8 Open | 100% | Open in Electronic Spark Timing (EST) circuit. Check plug wires. | ||
| 6 | EST 1-8 Short | 100% | Short in Electronic Spark Timing (EST) circuit. Check plug wires. | ||
| 7 | Fuel Injector 1-8 Open | 100% | Open in fuel injector circuit. | ||
| 8 | Fuel Injector 1-8 Short | 100% | Short in fuel injector circuit. | ||
| 9 | IAC Output | 90% | Faulty Idle Air Control (IAC) valve. Only with RPM | ||
| 10 | Knock Sensor 1 | 90% | Alarm sounds for 20 seconds in NEUTRAL, and indefinitely in gear. | ||
| 11 | Knock Sensor 2 | 90% | Alarm sounds for 20 seconds in NEUTRAL, and indefinitely in gear. | ||
| 14 | MAP Sensor 1 Input High | 90% | Short in Manifold Absolute Pressure (MAP) circuit (No visual on SC1000) | ||
| 15 | MAP Sensor 1 Input Low | 90% | Open in Manifold Absolute Pressure (MAP) circuit (No visual on SC1000) | ||
| 16 | MAT Sensor | 90% | Open or short in Manifold Air Temperature (MAT) circuit. | ||
| 17 | Oil PSI CKT Hi | 90% | Short in oil pressure circuit, defaults to 51.7 psi. | ||
| 18 | Oil PSI CKT Lo | 90% | Open in oil pressure circuit, defaults to 0 psi. | ||
| 20 | Port EMCT CKT Hi | 90% | Open in port Exhaust Manifold Coolant Temp (EMCT), defaults to 32°F. | ||
| 21 | Port EMCT CKT Lo | 90% | Short in port Exhaust Manifold Coolant Temp (EMCT), defaults to 32°F. | ||
| 24 | Sea Pump CKT Hi | 90% | Open in raw water pressure circuit. | ||
| 25 | Sea Pump CKT Lo | 90% | Short in raw water pressure circuit. | ||
| 26 | STB EMCT CKT Hi | 90% | Open in stbd Exhaust Manifold Coolant Temp (EMCT), defaults to 32°F. | ||
| 27 | STB EMCT CKT Lo | 90% | Short in stbd Exhaust Manifold Coolant Temp (EMCT), defaults to 32°F. | ||
| 30 | TPS1 CKT Hi | 90% | Short in Throttle Position Sensor (TPS) circuit, signal to 5v+, engine will not start. Refer to data monitor screen. | ||
| 31 | TPS1 CKT Lo | 90% | Open in Throttle Position Sensor (TPS) circuit. | ||
| 32 | TPS1 Range Hi | 90% | Above 4.8v, 994 counts in Throttle Position Sensor (TPS) circuit. | ||
| 33 | TPS1 Range Lo | 90% | Below 0.5v, 35 counts in Throttle Position Sensor (TPS) circuit. | ||
| 36 | 5 VDC PWR Low | varies | Short any 5v+ to ground. | ||
| No alarm | 29 | Steer CKT Hi | 100% | Open and short in steering angle sensor circuit. | |
| 34 | Trim CKT Hi | 100% | Short in trim sensor, high range, visual warning on SC1000 only. | ||
| 35 | Trim CKT Lo | 100% | Open in trim sensor, low range, visual warning on SC1000 only. |
Disclaimer: This chart applies to MerCruiser engines with PCM 555, including 496 MAG and 8.1S. Similar to ECM 555 engines (4.3, 5.0, 350, 6.2). This chart is for informational purposes only and is not necessarily applicable to any model. For more information, please check the official service manual.
How do You Clear the Codes on a MerCruiser?
Once you have fixed the malfunction, the fault code should disappear automatically.
If this does not happen, it’s a sign that the code is stuck in the ECM.
On older MerCruiser motors you can clear the error codes by simply disconnecting the batteries for 24 hours. Keep in mind that this trick won’t clear active fault codes.
On newer engines, the fault codes can usually only be cleared with a diagnostic scanner device.
Takeaways
MerCruiser diagnostic codes are also known as fault codes, error codes, or just DTC codes.
These codes refer to given malfunctions that can be decoded by the official MerCruiser DTC list.
MerCruiser fault codes can be pulled in many ways, including using a diagnostic tool, or even a VesselView Mobile App on the latest models.
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