KT200II & FoxFlash Volvo TRW EMS 2.2/2.3/2.4 Checksum Fix: Exact Tools, Tips & Step-by-Step Guide to Keep Your New FH4 Starting Every Time The Elephant in the Room: Why Your New Volvo FH4 Might Not Fire Up After a Tune Hey there, fellow wrench-turner! So you’ve just dropped some cash on a KT200II (or maybe the FoxFlash) to read and write the TRW EMS 2.2 v3, 2.3 and 2.4 ECUs found in the Volvo FH4, Renault T-Range and a handful of UD rigs. You already know these ECUs are built on rock-solid NXP MPC55xx / MPC5674F silicon and that you can hit them on the bench without popping the lid. That’s the easy part. The part that keeps tuners awake at night is the checksum. You’ve heard the horror stories - truck cranks, tach sweeps, no start, dashboard lit up like a Christmas tree. Nine times out of ten the culprit is an orphaned checksum. Let’s fix that once and for all. Quick Recap: What Is a Checksum Think of the checksum as the ECU’s “digital signature.” Every byte inside the cal...