302: Access 3 Logic Error #2, error in the U,V,W voltage feedback circuit: STEP1: Check line contactor is connected and getting proper voltage, 36v at pull-in then 24v continous. Check tips. STEP 2: Check traction motor cables at motor and Access 3 for shorts and continuity.

306: Voltage present at B+ terminal before powerup. STEP 1: Check line contactor tips. STEP 2: Check power cables are not shorted, if OK replace Access 3.

312: Line contactor driver open. STEP 1 Disconnect CA403 at Access 3 and check resistance between pin 26 and pin 27 on wire harness, should be 70-78ohms. If OK, step 3, if not ok, Step 2. STEP2: Disconnect line contactor coil wires and measure coil resistance, should be 70-78ohms. Out of range, replace coil, if in range, issue lies in wiring from Access 3 to coil on aformentioned pins. STEP 3: Replace Access 3

317: Brake Pedal Error, Brake Switch BRKS1 and brake pot POT2 mismatch. Go to Analyzer menu A2.2.3 and verify brake pot is between 15-20% when BRKS1 changes from zero to one as you slowly depress the pedal. Calibrate in calibration menu or manually adjust as required. There are a lot more fault finding steps for this code but normally its just a mismatch and I can't be bothered typing them all in.

Your major issue is in the first 3 codes, worry about those first...hope someone hasn't plugged a charger into the truck by mistake and fried Access 3!