What is the C1201 engine control system fault?
2 Answers
C1201 engine control system fault indicates an engine malfunction. The relevant explanations are as follows: 1. Introduction: This fault code is triggered when the engine malfunctions, causing the VSC skid indicator light to illuminate. The main inspection focuses are the engine and ABS system. 2. Additional notes: For the Toyota Crown 3.0, the fault code "C1201" means the starter is incompatible with the vehicle's computer or there is an issue with a small connector on the transmission. For the Toyota Camry, the fault "C1201" is often caused by issues with the catalytic converter, throttle body, or ABS sensor. After a series of troubleshooting and measurements, if no sensor issues are found, a road test should be conducted. When the engine reaches 2500 RPM, if the car shows signs of shaking, inspect the spark plugs. A slight damage to the spark plug in cylinder 5 may be found, and the ignition coil should be replaced.
Last time my car threw the C1201 trouble code, I specifically researched this issue. It's typically a problem with the electronic throttle control system. The most common causes are abnormal throttle position sensor signals or throttle plate sticking, causing the opening to not match the ECU's expectations. I've encountered this fault after cleaning the throttle without performing a relearn procedure - carbon buildup can cause the plate to stick in a mid-position and not return properly. A less common situation is wiring harness damage from rodent chewing leading to short circuits and incorrect signal voltage. When this happens, the car enters protection mode, and you'll noticeably feel lack of power during acceleration with RPMs not climbing properly. I recommend first reading the detailed fault flow to determine deviation values. If there's unstable idle accompanied by obvious jerking, don't force it - just call a tow truck.
