The engine P1694 Code problem may arise for different car engine problems. You need to fix problem but before that you should test the car engine properly. If you do not know the process of solving the car engine. Do not try to check or fix. The main problem of the car engine can be here depleted coolant. For this problem, leaks or faulty hoses may occur. So always test the car engine for the underlying cause before merely filling it up with more. That is why, you must not take any risk with the car engine. You fix the car engine under an expert engineer.