P2420EVAP System

Evaporative Emission System Switching Valve Control Circuit High

The control module has detected high voltage in the EVAP switching valve control circuit, usually indicating an open circuit, a short to power, or a valve that has failed open.

🚗 Yes. This emissions fault does not affect drivability, but repair it to pass emissions inspection.

LOW

severity

🎯 Top Causes, Ranked by Likelihood

#1Open in control wiring$80-$250

35%

A broken wire leaves the circuit open and reading high voltage.

#2Faulty switching valve$100-$300

30%

An internally open solenoid stops drawing current, raising the circuit voltage.

#3Short to voltage$80-$250

20%

The control wire contacts a power source and reads high.

#4Poor connector contact$40-$150

15%

Spread or corroded terminals create high resistance and a high reading.

🩺 Common Symptoms

Check engine light is on
EVAP monitor will not complete
No performance change
Possible failed emissions test

💰 Repair Cost: DIY vs Shop

DIY Cost

$100-$300

Shop Cost

$180-$450

📋 Free OBD2 Code Cheat Sheet

The 50 most common codes with likely cause and DIY fix cost. Sent once, no spam.

🔧 How to Diagnose P2420

1Inspect the valve connector and wiring for opens and corrosion.

2Check continuity of the control circuit and look for a short to power.

3Measure the solenoid resistance and replace if it reads open.

4Clear the code and complete an EVAP drive cycle to confirm.

❓ Frequently Asked Questions

What causes a high circuit code?

An open circuit or a valve that has failed open, both of which leave the control wire reading high voltage.

Can I keep driving?

Yes. It affects emissions only and does not change how the vehicle drives.

Is this usually a wiring problem?

Often yes. An open wire or bad connector is a common cause before the valve itself.

🔗 Related Codes

P2418P2419P2401P0455P0446