2010-2014 Hyundai Sonata (YF)HYBRID: Hybrid System Warning! Safely Stop and Do Not Drive. P1B77

TOOLS, STEPS, DIAGNOSTIC/STORY Power Relay Assembly Part Number 37514-4R000 Safety Connector (Electrical plug on internet) Part Number 37586-4R000 TOOLS NEEDED DTC Scanned which can access your car different Modules. Wrench Extensions 10mm, 12mm sockets Screwdriver (cross) Non contact voltage tester OR insulated electricians GLOVES rated for over 300 Volts. STRONGLY RECOMMENDED. YOU CAN DIE DOING THIS WORK. Steps Disconnect (-) cable from 12v battery Open little door behind the seat and pull the SAFETY PLUG for the hybrid battery unmount covers around the back of the rear seat (right side) Take your Rear seat and back rest off, pop the front (knees Part) of the seat, then wiggle it out (if you have rear heated seat be careful and unplug connectors), you will have access now to the 4 bolts (12mm) which hold the back part of the seat, remove and wiggle the Back part of the seat until it POPS out Remove the black cover for the hybrid battery about 6 screws cross heads Now remove the metal plate on the right side of the hybrid battery, one 10mm bolt and 3 Torx T35 bolts on the front and some 10mm in the back (trunk side) Now you can see the Power Relay Assembly. CHECK IF THE CABLES HAVE CURRENT OR USE GLOVES HERE Two 10mm nuts for the cables on top, three 10mm nuts on the front, unplug white harness on the back, take out three 10mm nuts holding the PRA at the bottom. Install everything following this steps backwards. At the end, use new SAFETY PLUG OR SAFETY CONNECTOR Diagnostic/Story time Strolling at a parking got the Dreaded "Hybrid System Warning! Safely Stop and Do Not Drive" After turning the vehicle off it wont start again. No "READY" indication on dash, hear a humming in the engine compartment and the ORANGE WRENCH shows on the dash. After many failed attempts the 12V battery was drained, towed home and proceed to diagnose here with the battery fully charged and booster connected to it to avoid discharge. Looking for fault codes HISTORY (NOT CHECK ENGINE LIGHT CODE, LOOK IN THE MODULES) I found the "P1B77" HISTORY not PENDING, as in, it was a detected problem but not a current problem. I cleared the CODE and it reads NO FAULTS now. When I push start with brake pedal in (as in to start the vehicle) WHILE MONITORING THE LIVE DATA ON THE SCANNER, It triggers the code fault again (P1B77) under the Battery Management System (BMS)MODULE. MORE DETAILS, when I go on the LIVE DATA on this MODULE BMS, with the KEY ON ENGINE OFF, I have: Available charge power 32000W (normal reading) Available Discharge Power 45490W (normal reading) As soon as I push start with the brakes in (to start the car) the WATTS GO TO ZERO ALSO on LIVE DATA SAME MODULE (BMS) BMS main relay on status indicator reads NO (Should Read YES) BMS controllable state reads NO (should read YES) BMS WARNING reads NO (correct) BMS FAULT reads NO (with KEY ON ENGINE OFF, Changes to yes when I try to start the vehicle.) Thus indicating there is a FAULT in the BMS module and the PRA is the culprit.