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P1400 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


P1400 is an OBD-II Code that refers to Engine Coolant Overtemperature Protection Mode Active


A P1400 code is a manufacturer specific trouble code related to vehicles such as BMW, Chevrolet, Ford, Mitsubishi, and Nissan and refers to failure for the Emissions Reduction Control System when performing a cold start. 

The purpose of the catalytic converter or to perform properly, which is efficiently reducing emissions, it must be maintained at a high temperature. That is why a cold-start strategy is implemented, which lowers the time it takes for the catalytic converter to reach operating temperature. During a cold start, the engine idle speed is high and the spark timing is delayed, allowing the catalyst to heat up faster. 

The fault code P1400 is set after a cold start is discovered, diagnostics are run, and if the actual exhaust power model does not match the expected exhaust power model.


Common causes for this code include:

  • There might be blockages or restrictions in the air intake system
  • The condition of the air filter may be poor
  • The throttle body or MAF Sensor may have some obstructions
  • There might be vacuum leaks in the engine
  • It’s possible the intake manifold is leaking
  • Recent modifications or obstructions in the exhaust system might be to blame


The symptoms of a P1400 code are:

  • The Check Engine lamp is lit
  • After a cold start, the car’s RPM drops to the point that it tries to shut down


To diagnose a P1400 DTC code, a technician would:

  1. Scan for codes in the ECM and look at the freeze frame data
  2. Examine the air intake system. Look for signs of damage, modifications, and restrictions in the system.
  3. Check the air filter element for dirt or signs of wear and damage.
  4. Check the crankcase ventilation system for proper operation. You can refer to the Crankcase Ventilation System Inspection/Diagnosis.
  5. Check for a vacuum leak and unmetered air flowing past the MAF (mass airflow) sensor.
  6. Examine the exhaust system for any signs of water intrusion or an exhaust leak.
  7. Next, look at the engine’s mechanical components for anything that might impact the amount of air entering the combustion chamber.

Common mistakes

The following are some of the most common mistakes that a technician may make when diagnosing a P1400 code:

  • Not checking the freeze frame data to determine the conditions under which the DTC was set
  • Not checking for proper operation of the Crankcase Ventilation System
  • Failure to check the engine’s mechanical components, which can impact air flow into the combustion chamber
  • It must be noted that this list is not complete and only contains some of the most common mistakes. Other mistakes may exist, so it is always best to consult with a professional technician if you are having trouble with your car.

How serious is this?

A P1400 code is considered to be moderate, meaning the car will still run, but there might be a considerable decrease in performance.

What repairs can fix the code?

The following are solutions that may fix this problem:

  • Repair damage or replace the air intake system
  • Remove any carbon that has collected in the throttle bore
  • The MAF (mass airflow) sensor elements should be cleaned

Related codes

A P1400 is related to and may be accompanied by the following codes:

P0100 – Mass or Volume Air Flow Circuit Malfunction

P0101 – Mass or Volume Air Flow Circuit Range/Performance Problem

P0102 – Mass or Volume Air Flow Circuit Low Input

P0103 – Mass or Volume Air Flow Circuit High Input

P0104 – Mass or Volume Air Flow Circuit Intermittent


In conclusion, the P1400 code is a diagnostic trouble code that refers to a malfunction in the vehicle’s exhaust power model. This code can be caused by a number of issues in a vehicle’s components, including any obstructions in the intake or exhaust system. Other mistakes commonly made when diagnosing this code consist of not checking for proper operation of the Crankcase Ventilation System and neglecting to check other engine mechanical components that may impact air flow into the combustion chamber.

The P1400 code is considered to be moderate, meaning it will have an affect on performance but won’t keep the car from running properly. If you suspect your car has this DTC, make sure to get it repaired as soon as possible before your vehicle becomes undrivable.