EVAP Vent Valve Output Circuit High (Honda)
What does P1666 mean?
The P1666 code means the vehicle's onboard diagnostic system has detected: EVAP Vent Valve Output Circuit High (Honda). This is a low severity code.
Common Symptoms
- Check Engine Light on
- Fuel vapor odor
- Difficulty filling gas tank
- Failed emissions test
- Slow fuel filling at pump
Probable Causes (Ranked by Likelihood)
- Short to voltage in vent valve wiring Very High
- Faulty EVAP vent valve solenoid stuck open High
- Water intrusion in vent valve connector Moderate
- ECU internal short on vent valve driver Low
Step-by-Step Diagnostic Procedure
-
Disconnect the vent valve solenoid connector and clear the code. If the code changes to a low circuit code, the solenoid is shorted.
-
Inspect the vent valve wiring harness for damage, chafing against metal, or rodent damage.
-
Measure voltage at the vent valve connector with it disconnected and ignition on. Should read 0V when not commanded.
-
Check for water or corrosion inside the vent valve connector, especially on vehicles driven in wet climates.
-
If wiring is good and the solenoid resistance is correct, suspect an ECU driver issue.
Frequently Asked Questions
What does a high circuit code mean?
A high circuit code means the ECU is detecting higher voltage than expected on the vent valve control wire, indicating a possible short to power or internal solenoid fault.
Can rodent damage cause this code?
Yes. Rodents commonly chew wiring under the vehicle near the fuel tank area where the EVAP vent valve is located.
Is this code related to the gas cap?
Not directly. P1666 is specific to the vent valve electrical circuit, while a loose gas cap typically sets P0455 or P0456.