Fault code P1144 – a step-by-step guide to diagnosing and fixing it

Error code P1144 is displayed and the check engine light is on - what does this mean?

DTC P1144 is triggered by the OBD/EOBD system if the lambda sensor upstream of the catalytic converter (bank 1, sensor 1) does not show sufficient activity or does not switch properly between rich and lean. This manufacturer-specific trouble code mainly occurs in Ford, Mazda and some other vehicles and indicates problems with the fuel-air mixture control.

What can cause this error code?

• Defective lambda sensor upstream of the catalytic converter
• Contaminated or poisoned oxygen sensor
• Damaged cables or plug connections to the lambda sensor
• Defective lambda sensor heater
• Vacuum leaks in the intake tract
• Blocked fuel injection valves
• Defective fuel pump or low fuel pressure
• Dirty mass air flow sensor
• Defective engine control unit (ECU)
• Exhaust leaks upstream of the lambda sensor

What symptoms occur in parallel with fault code P1144?

• Engine performance: Reduced engine power and poor acceleration
• Fuel consumption: Increased fuel consumption due to inaccurate mixture control
• Idle problems: Unsteady idling or idling fluctuations
• Exhaust emissions: Increased pollutant levels and poor exhaust emissions
• Starting behavior: Difficult cold starts or prolonged warm-up
• Engine noise: Irregular engine running or jerking while driving

How can the problem with fault code P1144 be rectified?

• Repairing fault code P1144 requires a systematic diagnosis of the fuel-air mixture control system.
• Replace the lambda sensor upstream of the catalytic converter (bank 1, sensor 1) completely, including a new seal and professional installation with the correct tightening torque
• Check wiring harness and plug connections to oxygen sensor for damage, corrosion or loose contacts and repair or replace if necessary
• Locate and seal vacuum leaks in the entire intake tract, checking hoses, gaskets and intake manifold in particular
• Clean the fuel system by replacing the fuel filter, cleaning the injection valves and checking the fuel pressure
• Remove the mass air flow sensor, clean it with a special cleaner or replace it completely if it is very dirty
• Check the exhaust system for leaks before the lambda sensor and weld leaks or replace pipes