OBD-II Code P1400 — What It Means & How to Fix It

What Does This Error Mean?

P1400 is a manufacturer-specific code with different meanings depending on the vehicle brand. On Nissan and Infiniti it indicates a DPFE (Differential Pressure Feedback EGR) sensor circuit fault. On Mitsubishi it points to a Cold Start Emission Reduction Control System fault. On Honda it may indicate an EGR valve position sensor fault. The common thread is an emissions or EGR-related circuit issue.

Affected Models

Common in Nissan Altima, Maxima, and Frontier with EGR systems
Common in Mitsubishi Eclipse, Galant, and Outlander
Common in Infiniti G35 and I30
Common in Honda Accord and Civic on some model years

Common Causes

Faulty DPFE sensor or EGR pressure sensor sending out-of-range voltage
Clogged or stuck EGR valve preventing proper exhaust gas recirculation
Cracked or disconnected EGR vacuum hose reducing pressure signal
Damaged wiring or connector at the EGR sensor or solenoid
Carbon buildup in EGR passages blocking flow and causing pressure irregularities

How to Fix It

Look up the exact P1400 definition for your specific vehicle make and model year before starting diagnosis.

P1400 means different things on different vehicles. A generic scanner may not display the correct definition.
Visually inspect all EGR vacuum hoses for cracks, kinks, or disconnections.

Cracked hoses are a common cause of EGR system faults and are inexpensive to replace.
On Nissan and Infiniti vehicles, locate the DPFE sensor and check the wiring harness and connector for damage.

Measure sensor output voltage with a multimeter and compare to specification.
Inspect the EGR valve for carbon buildup. Remove it and check if it opens and closes freely.

Carbon-clogged EGR valves are common on high-mileage engines. Cleaning with EGR cleaner spray often restores function.
Replace the faulty sensor or EGR valve as indicated by your diagnosis. Clear codes and drive through a complete drive cycle.

The EGR monitor must complete to confirm the repair. This usually requires a warm engine and steady highway driving.

When to Call a Professional

DPFE or EGR pressure sensor replacement is $50 to $120. EGR valve replacement is $100 to $300 in parts. Carbon cleaning of EGR passages is $150 to $400 at a shop. Always confirm the exact definition of P1400 for your specific make before replacing parts.

Frequently Asked Questions

Does P1400 affect how my car drives?

It depends on the severity. In many cases the car runs normally with only a check engine light. If the EGR valve is stuck open, the engine may idle roughly and hesitate during acceleration. A stuck closed EGR valve usually has little effect on driveability.

Can I clean the EGR valve myself to fix P1400?

Yes, in many cases. Remove the EGR valve and spray EGR cleaner or carburetor cleaner into the valve. Work the valve open and closed by hand while cleaning. This often restores proper operation without buying a new valve.

Will P1400 cause me to fail an emissions test?

Yes. Any code that turns on the check engine light will fail an emissions inspection. Also, if the EGR monitor has not completed, your vehicle may fail for incomplete readiness monitors.