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P2426 — Egr Cooling Valve Control Circuit Low

Manufacturer-specificPowertrain (engine & transmission)

OBD-II code P2426 indicates that the powertrain control module (PCM) has detected a low voltage condition in the control circuit for the exhaust gas recirculation (EGR) cooler bypass valve. This valve regulates exhaust flow through the EGR cooler to manage gas temperatures and prevent cooler clogging. A low circuit voltage typically points to a short to ground, an open circuit, or a faulty valve solenoid.

Symptoms

What causes it — most likely first

1. Faulty EGR cooler bypass valve solenoid

The solenoid coil may be shorted internally or have high resistance, causing the control circuit voltage to drop below the expected range.

2. Wiring harness short to ground

Chafed or pinched wiring in the EGR cooler bypass valve circuit can contact the engine or chassis ground, pulling the signal voltage low.

3. Open circuit in the control wiring

A broken wire or disconnected connector between the PCM and the valve solenoid interrupts current flow, which the PCM interprets as a low voltage condition.

4. Poor electrical connections at the valve or PCM

Corroded, loose, or bent terminals at the valve connector or PCM harness can increase resistance and cause a voltage drop.

5. Short to voltage in the signal return circuit

A wiring fault that allows the signal return line to contact a power source can create a voltage offset that mimics a low control circuit reading.

6. Failed PCM (rare)

An internal fault in the PCM's EGR cooler bypass valve driver circuit is possible but highly unlikely; this should only be considered after all other causes are ruled out.

How it's diagnosed

  1. Visually inspect the EGR cooler bypass valve, wiring harness, and connectors for obvious damage, corrosion, or disconnection.
  2. Check the valve solenoid resistance with a multimeter and compare to manufacturer specifications; replace the valve if out of range.
  3. Test the control circuit for a short to ground by disconnecting the PCM and valve, then measuring resistance between the control wire and chassis ground.
  4. Verify the control circuit for an open by checking continuity between the PCM connector and the valve connector.
  5. With the valve connected and engine running, use a scan tool to command the valve on/off and observe the control circuit voltage; a stuck-low reading suggests a wiring or PCM issue.
  6. If all wiring and the valve test good, perform a PCM self-test and check for internal driver faults, but only after eliminating all other possibilities.

Code facts & related codes

SystemPowertrain (engine & transmission)
StandardizationManufacturer-specific (P1/B1/C1/U1)
Related codesP2420 — Evap System Switching Valve Control CiP2421 — Evap System Vent Valve Stuck OpenP2422 — Evap System Vent Valve Stuck ClosedP2423 — Hc Adsorption Catalyst Efficiency BeloP2424 — Hc Adsorption Catalyst Efficiency BeloP2425 — Egr Cooling Valve Control Circuitopen

Frequently asked

What does the P2426 code mean?

It means the PCM has detected a low voltage condition in the electrical circuit that controls the EGR cooler bypass valve, which manages exhaust gas temperature through the EGR cooler.

Is it safe to drive with a P2426 code?

In most cases, the vehicle remains safe to drive, but prolonged operation may lead to reduced fuel efficiency, increased emissions, or potential damage to the EGR cooler if the valve is stuck in the wrong position.

What is the most common fix for P2426?

Replacing a faulty EGR cooler bypass valve solenoid or repairing damaged wiring/connectors in the control circuit are the most frequent repairs.

Could a bad PCM cause the P2426 code?

It is extremely rare. The PCM is often misdiagnosed as the cause, but the issue is almost always a wiring fault, connector problem, or a failed valve solenoid. The PCM should only be suspected after thorough testing of all other components.