Generac Error Code 1501

What the code means

The controller watches engine speed. When the signal it expects isn't there, it shuts the engine down and posts a code in the RPM Sense Loss group. Generac doesn't publish a separate meaning for 1501 versus its neighbors such as 1505, and says the owner troubleshooting is the same whichever one you have. Generac's app message for this group reports an RPM sensor alarm and tells you to contact a dealer.

On the older air-cooled units in Generac's 2012 owner's manual, the controller shuts down and locks out when there's no valid RPM signal within 3 seconds of cranking, and if the signal drops out while running it retries once before locking out.

Note when it happened. A code that showed up mid-run, with the house on generator power, points a different way than one that appeared on a weekly exercise.

Common causes

Generac's list is short: a weak or bad battery, the fuel system, an overload, a sudden load change, or missed maintenance. The load items are worth a hard look on this code. Motor loads can pull 3 to 4 times their running wattage when they start, so a well pump and an air conditioner kicking on together can drag the engine down.

What you can safely check

1. Battery. If the display says CHECK BATTERY, have it tested and replace it if needed; Generac puts typical battery life at 3 to 5 years. A voltmeter only shows voltage is there, so ask an auto parts store for a load test.
2. Terminals. Above 12.6 volts, check that the cables and terminals are clean, free of corrosion and tight.
3. Fuel. Make sure the fuel shutoff valve is open and the controller's fuel setting matches your gas type. On propane, Generac says fuel pressure may suffer below about 30% in the tank.
4. Air filter. Look for a clogged filter, and in winter, snow or ice in the air path.
5. Load. Turn off non-essential loads and run the unit with no load to see whether load is the problem. Bring critical circuits back first, then the rest a few at a time.
6. Restart. Clear the alarm at the panel and press the blue MANUAL button, and never start the generator under load.

When to call a dealer

Call a Generac authorized service dealer if the code keeps returning after those checks, if the unit won't start in AUTO during an outage even with a good battery, or if it trips during exercise or comes and goes. If it happened during installation, call your installer. Leave the code on the display and have your maintenance records ready.