If your Generac Evolution 1.0 or 2.0 series generator shows error code 1505, it means the control system commanded the engine to crank but did not receive confirmation that the engine was actually turning. This is often called an RPM sensor loss alarm. Understanding this code can help you troubleshoot before calling a technician.
What Causes RPM Sensor Loss (Code 1505)?
This error typically occurs on two-cylinder units during cranking. The controller expects to see a signal indicating engine rotation, but it doesn’t. Common reasons include:
- Dead or weak 12V battery unable to power the starter motor
- Faulty starter motor or damaged wiring to the starter
- Ignition coil problems preventing the sensor from detecting RPM
For single-cylinder units, a related code (1511) can indicate the engine stalled or lost RPM signal while running, often due to fuel supply issues or engine overload.
Diagnostic Checklist
- Check the Battery Voltage: Use a multimeter to verify the battery is fully charged (around 12.6 volts or higher). A weak battery may not crank the engine properly.
- Inspect Battery Connections: Ensure battery terminals are clean, tight, and corrosion-free to guarantee good electrical contact.
- Listen for Starter Engagement: When the generator tries to start, listen for the starter motor turning. If silent or slow, the starter or wiring may be faulty.
- Examine Starter Wiring: Visually inspect wiring from the battery to the starter for loose connections, frayed wires, or damage.
- Check Ignition Coil and Sensor Wiring: Look for disconnected or damaged ignition coil wires, as these can cause the RPM sensor to lose signal.
- Verify Fuel Supply (for single-cylinder units): Confirm the LP tank is not empty and fuel lines are intact to prevent stalling-related RPM loss.
- Reset the Generator: After checking connections and battery, reset the unit per the manual and attempt to start again to see if the code clears.
- Review Load Conditions: Avoid sudden heavy loads during startup which can stall the engine and trigger RPM loss alarms.
When to Call a Pro
If you’ve completed the checklist and the error persists, or you notice any of the following, it’s time to contact a qualified technician:
- The starter motor makes unusual grinding or clicking sounds
- Battery tests good but the engine still does not crank
- Ignition coil or sensor wiring appears damaged but you’re unsure how to safely repair
- Generator stalls repeatedly during operation or the fuel system shows signs of leaks
- You are uncomfortable working with electrical components or fuel systems
Parts You May Need
- 12V battery
- Starter motor
- Ignition coil
- Battery cables and connectors
- Fuel line or LP tank (if applicable)
FAQ
What does error code 1505 mean on my Generac generator?
It means the controller did not detect engine rotation during cranking, indicating an RPM sensor loss.
Can I fix error code 1505 myself?
Yes, if you are comfortable checking battery charge, wiring, and connections, you can perform basic troubleshooting. Otherwise, call a professional.
Does a low battery cause RPM sensor loss?
Yes, a weak or dead battery may prevent the starter from turning the engine, causing the controller to detect no RPM signal.
What is the difference between error codes 1505 and 1511?
Code 1505 occurs during cranking on two-cylinder units when no RPM is detected, while 1511 happens on single-cylinder units that stall or lose RPM signal while running.
Disclaimer: This is general information only. Always follow the manufacturer’s manual and safety instructions for your specific Generac model.
Source: Information adapted from official manufacturer documentation (reference). Always consult your generator owner’s manual for model-specific procedures.