If your vehicle is showing engine goes into limp mode or displays a reduced engine power warning, here are the most likely causes and the parts you'll need to fix each one.
A failure in the throttle body, throttle position sensor, or accelerator pedal sensor is the most common trigger for limp mode. The computer restricts power because it cannot safely verify the driver's throttle input.
If the engine computer receives erratic or missing data about incoming air, it will default to a safe, low-power mode. This frequently happens if the MAF sensor is left unplugged after checking the air filter, or if the sensor is dirty.
A dead ignition coil or severely worn spark plug can cause a major misfire. To protect the catalytic converter from unburned fuel, the engine computer will flash the check engine light and cut engine power.
The VVT system relies on engine oil pressure to adjust valve timing. Low oil levels, dirty oil, or a clogged VVT solenoid will cause timing to fall out of spec, immediately triggering limp mode to prevent internal engine damage.
If the transmission control module detects internal slipping, low fluid, or receives a bad reading from a speed sensor, it will lock the transmission into a single gear (usually 2nd or 3rd) and command reduced engine power.
In turbocharged vehicles, if the boost pressure sensor detects too much or too little pressure due to a failing wastegate or vacuum leak, the computer cuts power to prevent the engine from blowing up.
A rare catastrophic failure where the main computer itself shorts out or suffers internal board degradation, causing it to falsely trigger limp mode or lose communication with the rest of the vehicle.