The B1638 Code is related with the engine and every manufacturer setup the engine code but different manufacturer set the meaning of the code differently. The dictionary meaning of the code is B for Body Code Problem is antilock brake system, electronic suspension and steering systems. 1 for MFG – Manufacturer Specific. 6 for Vehicle Speed Control and Idle Control System. 3 for Cruise Control Servo Indicates Low and 8 for PCM Stack Overrun. The body of the engine has the main problem and the component from the engine is not necessary to remove or change. You should take the car for test drive.