The B1390 Code is a fault code of an engine and this code is not easy to describe until you get the name of the manufacturer and model. The code may have different meanings. The meaning of the code is B for Body Code Problem is antilock brake system, electronic suspension and steering systems. 1 for MFG – Manufacturer Specific. 3 for IC Module 4X Ref Circuit Intermittent, No Pulses. 9 for Crankshaft Position Sensor Circuit Performance and 0 for Transmission Engaged at High Throttle Angle. Now it is easy to understand what the problem is of the engine of the car.