1999 GMC Jimmy V6 4.3L with P1902 and Multiple DTC Codes: Engine Hesitation, Brake Light On, Power Loss on Hills

I own a 1999 GMC Jimmy (4WD, SLE trim, V6 4.3L engine) with approximately 140,000 kilometers. The vehicle has recently developed several driving issues and I'm seeking help to diagnose the root cause. SYMPTOMS: - Engine warning light comes on steadily while driving - Anti-lock brake (ABS) warning light activates during operation - On hills, engine power is noticeably weak; acceleration feels sluggish or hesitant - During acceleration, the vehicle hesitates and occasionally jerks - Backfiring through the exhaust pipe occurs while driving - From a stop, initial forward movement is slow (sluggish), then improves after a few seconds - During at least one gear shift, the engine races before the transmission engages, accompanied by a bouncing tachometer needle - In wet weather conditions, the engine light flashes yellow and then stabilizes to steady after deceleration; it turns off when roads dry out I recently performed maintenance including: plug and wire replacement (cap and rotor not replaced), fuel filter change, water pump replacement, coolant flush, idler arm, tie rod, and front wheel bearing repairs. DTC CODES RECORDED AT LOCAL SHOP: - P1902 – Transmission-related code (GM-specific) - P03003 – Cylinder misfire detected - C0225 – Left Front Speed Sensor fault - C0226 – Right Front Speed Sensor fault - C0227 – Left Front Wheel Speed Sensor erratic reading - C0225 (duplicate) – Left Front Speed Sensor open circuit WHAT IS WRONG WITH MY CAR? I understand that P19xx codes are specific to GM transmissions. However, I'm unsure what the exact meaning of P1902 is and how it relates to my symptoms. Can anyone explain what P1902 means in a 1999 GMC Jimmy? How do these DTCs affect engine performance, transmission behavior, or safety features like ABS? Any insights into potential causes — especially related to sensor faults, misfires, or transmission issues — would be greatly appreciated.