P2420

Switching Valve Control Circuit High (Evaporative Emission System)

P2420 is a generic OBD-II powertrain diagnostic trouble code: Switching Valve Control Circuit High (Evaporative Emission System). It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P2420
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
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What P2420 means

P2420 is set when the PCM detects a high-voltage condition on the control circuit for the EVAP switching valve, also referred to on some platforms as the EVAP vent valve or a secondary switching valve in the evaporative emission system. The PCM drives this valve to open or close the EVAP canister vent path during diagnostic testing; monitoring of the driver circuit detects electrical faults in real time.

A high-circuit fault on a valve control circuit usually indicates a short to battery voltage on the solenoid control wire. This condition can hold the valve in the wrong state, preventing the PCM from executing the EVAP large-leak test or the purge flow diagnostic, which will cause one or more EVAP monitors to fail to run. The valve is normally located near the charcoal canister, which may be under the vehicle or in the engine bay depending on the platform.

Diagnosis should start with a visual inspection of the valve and its harness. Measure the control circuit voltage, confirm the supply and ground are correct, and perform a PCM-commanded solenoid test if the scan tool supports it. Repair wiring faults before replacing the valve.

Common causes

Most-frequently reported root causes when P2420 is logged.

  • 1
    Short to battery voltage in the EVAP switching valve control wire.
  • 2
    Damaged harness where the control wire contacts a 12 V source.
  • 3
    Failed valve solenoid with internally shorted windings.
  • 4
    Corroded connector terminal creating a high-side leakage path.
  • 5
    PCM driver circuit fault producing an out-of-range output voltage.
  • 6
    Water intrusion into the valve or its connector causing an internal short.
  • 7
    Prior wiring repair that inadvertently connected the control wire to a supply circuit.

Symptoms drivers notice

MIL on with P2420 stored.
EVAP system monitors incomplete or flagged as failed.
Possible fuel vapor odor if the valve is stuck in the wrong position.
No significant drivability concerns in most cases.

How to diagnose P2420

A typical diagnostic flow when this code is present.

  1. 1
    Read all DTCs and note any companion EVAP system or purge-related codes.
  2. 2
    Locate the EVAP switching valve and inspect the connector and harness for damage.
  3. 3
    Measure the control circuit voltage at the connector with key on; it should not exceed battery voltage on the signal side before PCM actuation.
  4. 4
    Measure valve solenoid resistance and compare to specification.
  5. 5
    Use a scan tool to perform a solenoid actuation test and observe circuit response.
  6. 6
    Trace the control wire for shorts to battery voltage between the connector and PCM.
  7. 7
    Repair identified faults, clear codes, and verify EVAP monitors complete on the next drive cycle.

Vehicles where we've handled P2420

Platforms in our catalogue with confirmed P2420 coverage.

BMW 320D
2016

Related powertrain codes

Frequently asked questions

Will P2420 cause drivability problems?

Usually not directly. The main effect is that EVAP diagnostic monitors will not complete, and the MIL will be on.

Is the EVAP switching valve the same as the purge valve?

Not necessarily. Some vehicles have separate purge and vent/switching valves. Check the wiring diagram to confirm which valve is associated with the P2420 circuit on your specific application.

Can P2420 cause a fuel smell in the cabin?

If the valve is stuck open due to the circuit fault, vapor may not be properly managed, potentially resulting in a mild fuel odor.

Do I need to replace the PCM if the wiring checks out?

Test the PCM driver output as directed in the service manual before condemning it. PCM failures causing this code are uncommon.

Disabling P2420 in software

RaceTune can permanently disable P2420 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

ECUs with a P2420 disable in our catalogue

Confirmed coverage from our recipe database — we support many more families. Upload your file and our identifier will match it automatically.

  • Bosch EDC17C50 verified 1 software version

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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