The computer system that controls your car has a built in safety feature called "Reduced Power" or "Limp Mode" which is designed to get the car where it is going under low engine power while protecting the car's engine and transmission. When a malfunction is detected by the computer either from the engine management system or transmission the car should show a Reduced Power and/or the Check Engine Light, some cars will also trigger a Traction Control Light. This can sometimes be reset by pulling over and shutting the key off, then once the car is restarted the limp mode can be reset as well, this can help get you to your destination. The Limp mode condition will return until repair or services have been performed and codes are cleared. Sometimes it can take being in this mode for some time before the check engine light will illuminate.
Engine: The number #1 problem to cause limp mode is a dirty throttle actuator which can be cured by a simple throttle body cleaning. This condition occurs after the car ages and begins to develop a substance call "Coking" which resembles a thin brown tar on its throttle bore actuator and butterfly. When this happens the response time between the throttle pedal sensor and the actuator increases causing a correlation issue. This condition can also be accompanied by either throttle pedal or throttle actuator trouble codes.
Transmission: The internal parts of the transmission such as the shift solenoids are controlled using wiring for their connections which over time can become shorted causing the computer to detect a fault. This can happen for the various transmission feedback sensors such as the fluid pressure and temperature as well. Also, shift solenoids are subject to metal debris which occurs naturally over time inside the transmission's moving parts. Because if this a shift solenoid can become unresponsive which can cause the reduced power condition.
The cost for this repair can be surprisingly inexpensive depending on the failure. To determine what the failure is a CAN or Engine scan will need to be performed. This can be done with a simple scanner which costs about $40.00 on Amazon. Here is a link to one of our favorites, CAN scanner this will help determine what the issue is.
You can avoid the limp mode issue by keeping up and the maintenance of your vehicle such as an engine tune up which include the throttle bore service and changing out the transmission fluid and filter at the regulator recommended intervals.
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