Generac error 1100 indicates the controller has lost the engine speed signal from the magnetic pickup sensor. The primary fix is cleaning debris from the sensor tip and readjusting the air gap between the sensor and the flywheel teeth.
Code 1100 is honestly one of the more fixable faults I see on Generac standby units. Nine times out of ten it's a dirty sensor tip or a gap that vibrated out of spec. Ignore it and your generator won't start when the power actually goes out, which is basically the worst time to find out. Usually under an hour to fix if you've got a feeler gauge and aren't afraid to get a little dirty.
Phillips #2 screwdriver, 10mm or 13mm socket with ratchet (varies by model)
What Does the 1100 Code Mean?
Here's the deal with 1100. The magnetic pickup sensor reads teeth on the flywheel like a gear-tooth counter, and if that signal disappears, the controller panics and shuts everything down. What catches most people off guard is that this is usually a $20 sensor or a free cleaning job, not a $500 control board. I've seen engines run great for years then start throwing this code just because a field mouse chewed halfway through the wiring over one winter.
Most Likely Causes
Based on aggregated repair data, here is the probability breakdown for this error code:
Debris between sensor and flywheel teeth40%
Sensor air gap too wide from vibration24%
Sensor connector corroded14%
Wiring harness chafed or damaged12%
Magnetic pickup sensor failed10%
Symptoms You May Notice
The controller display locks up with a solid 1100 alarm and the unit refuses to restart until you manually clear it
Engine was running fine then just cut out mid-cycle with zero warning
RPM hunting or surging for a few seconds right before it dies, kind of like it's gasping
Complete loss of output power during an actual outage, which is obviously the worst possible timing
Sometimes shows up alongside 1505 or other speed-related codes all at once
Can you reset a Generac generator to clear the 1100 code?
Hit the OFF button to clear the active alarm. Once you've cleaned the sensor and set the gap to 0.030 inches, press MANUAL and let the engine run five full minutes without the code returning. If it holds steady, press OFF then AUTO to drop it back into standby mode. If 1100 comes back, you've still got an issue in the sensor, wiring, or flywheel.
Tools Required for Diagnosis
Phillips #2 screwdriver10mm or 13mm socket with ratchet (varies by model)Digital multimeter set to ohmsFeeler gauge set with 0.030-inch bladeElectrical contact cleaner sprayShop rag or paper towelsFlashlight or headlamp
Diagnostic Checklist
Follow these steps in order. We start with the easiest external fixes before opening up the machine.
ComponentComponent Under Test
Expected Range900–1200 ohms
ConditionIf Open (OL) or infinite, replace component.
Replacement Parts
If your diagnostic testing proves the component has failed, you will need a replacement. We recommend OEM parts over aftermarket for water-handling components.
Part Name
OEM Number
Estimated Price
Generac RPM Magnetic Pickup Sensor0G5445 · $30–$60
0G5445
$30 – $60
Feeler gauge setN/A · $5–$10
N/A
$5 – $10
Dielectric greaseN/A · $5–$8
N/A
$5 – $8
Frequently Asked Questions
Can 1100 cause engine damage?
No, the shutdown is actually protecting the engine. The controller lost the RPM signal and doesn't know if the engine seized, oversped, or just lost a wire, so it shuts down fast to be safe. The real danger isn't damage to the generator itself. It's that your backup power is down. Being stuck without power in a storm because the generator threw a code that probably takes 20 minutes to fix is the actual problem here. It's a safety shutdown, not a sign of a blown motor.
My Generac shows 1100 only during exercise. Why not during outages?
Classic symptom of a sensor that's right on the edge of failing. During the weekly exercise cycle, the vibration frequency and load conditions are slightly different than during a real outage running at full load. That subtle difference is enough to push a marginal signal over the edge during exercise but not during a heavier load cycle. If it's only failing during exercise right now, treat it as a warning shot. It will fail during an actual outage eventually, probably on the worst night of the year.
How much does it cost to fix a 1100 fault?
If you just need to clean the sensor and reset the gap, it's basically free. If the sensor itself needs replacing, the magnetic pickup runs about $25-$45 depending on your model, and it's maybe 30 minutes of work. If the wiring harness is chafed all the way back toward the controller, you're looking at $80-$150 in parts plus the time to route and secure new wiring. Flywheel ring gear damage is a bigger job and a lot more expensive, but honestly that's pretty rare on units that've been maintained properly.
How often should the RPM sensor be checked?
Pull it and wipe it down every two years as part of your deep maintenance, same time you're checking valves and swapping plugs. Takes five minutes. Way easier to clean a little metal dust off now than to troubleshoot a dead generator at midnight in a blizzard. If you're running the unit hard during long multi-day outages, bump that to every year. Honestly this sensor is one of those parts that fails silently and slowly, so periodic checks are the only way to catch it before it leaves you in the dark.
What's the part number for the Generac RPM sensor?
The most common replacement is Generac part A0000017735, but it varies by model year. Some older units use 0A4614 or 0C3382. Best bet is to pull the sensor out and look for a number stamped on the body, or plug your full model number into Generac's parts lookup. The connector type and thread pitch have to match exactly or you'll fight it getting the gap dialed in right. When in doubt, call your local Generac dealer with the serial number and they can look it up in about two minutes.