Cummins Generator Error Code 335: How to Fix It
Medium 1-2 hours Medium Severity
Verified June 2026
- Error Code
- 335
- Brand
- Cummins
- Product Type
- generator
- Severity
- Medium
- DIY Difficulty
- Medium
- Estimated Fix Time
- 1-2 hours
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Tools You'll Need
- Multimeter
- Electrical contact cleaner
- Cummins INSITE™ or compatible diagnostic scan tool
- Basic hand tools (screwdrivers, wrenches)
How to Fix Error Code 335
-
Safety First – Disconnect Power and Battery
Always disconnect the battery before working on the ECM or wiring. The generator may start unexpectedly if the battery is connected. -
Inspect Wiring and Connectors
-
Check for Diagnostic Codes with a Scanner
Do not clear codes before documenting them. Some codes may require a specific key cycle or engine run to reappear. -
Verify Sensor Connections and Function
Never short sensor wires to ground or battery voltage. Use proper testing procedures to avoid damaging the ECM. -
Check Power and Ground to ECM
Reconnect the battery carefully. Do not start the engine during this test unless instructed by a service manual. -
Clear Error Code and Test Run
-
Replace ECM if Necessary
ECM replacement is complex and may require professional programming. Consider calling a Cummins service technician.
Parts You May Need
Engine ECM (Electronic Control Module)
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Sensors (coolant temp, oil pressure, etc.)
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Wiring harness or connector repair kit
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Engine ECM (Electronic Control Module)
Check Price on Amazon
Sensors (coolant temp, oil pressure, etc.)
Check Price on Amazon
Wiring harness or connector repair kit
Check Price on Amazon
Engine ECM (Electronic Control Module)
Check Price on Amazon
Sensors (coolant temp, oil pressure, etc.)
Check Price on Amazon
Wiring harness or connector repair kit
Check Price on Amazon
Engine ECM (Electronic Control Module)
Check Price on Amazon
Sensors (coolant temp, oil pressure, etc.)
Check Price on Amazon
Wiring harness or connector repair kit
Check Price on Amazon
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When to Call a Professional
If you have checked all wiring, sensors, and power grounds and the code still appears, or if you suspect an ECM failure, call a certified Cummins technician. ECM replacement often requires specialized programming and calibration tools.Frequently Asked Questions
What does Cummins generator error code 335 mean?
Error code 335 indicates an Engine ECM Warning. The ECM has detected an abnormal condition that could affect engine performance. It's a generic warning that requires diagnostic scanning to identify the root cause.
Can I clear error code 335 myself?
Yes, you can clear the code using a Cummins INSITE™ scan tool or a compatible diagnostic device. However, if the underlying issue is not fixed, the code will return. Clearing without repair is only for testing.
What tools do I need to diagnose error code 335?
You'll need a multimeter for electrical checks, electrical contact cleaner for connectors, and a Cummins INSITE™ or compatible diagnostic scan tool to read and clear codes. Basic hand tools may be required for access.
Is it safe to run the generator with error code 335?
It depends on the severity of the underlying issue. Running the generator could lead to poor performance or further damage. It's best to diagnose and repair the problem before continuing use.
How much does it cost to fix error code 335?
Costs vary widely. Simple sensor or wiring repairs may cost under $100 for parts. ECM replacement can cost $500–$2000+ including parts and labor. Professional diagnostic fees also apply.