The engine C1242 Code is very important thing and getting the true meaning of the code is necessary to know. Do not follow common meaning for solving the car engine. The engine code C1242 OBD2 may also be generated by the faults former down the line. Such as a dirty MAF sensor might be producing the car to overreact in its fuel-trim adjustments. So, the oxygen sensors are likely to report fuel mixture problems. The C1242 engine code is a kind of chassis problem and it is easy to solve. The oxygen sensors on your car count the oxygen in the finish to determine how rich the ratio of fuel and air are in the cylinders.