How to back up your Nissan ECU with a KKL cable

Before you change anything on your ECU, save a copy of what's on it now. If a tune doesn't work out, you can flash the backup and the car is exactly as it was. Reading the ECU doesn't change anything in the car, and with VQLab Lite it's free.

What you need

• A Windows 10 or 11 laptop you can take to the car, and its charger.
• A K-line (KKL) USB cable with a CH340 chip, sold as a "VAG 409.1 KKL" cable for about $10. FTDI cables look the same but don't work. See the cable guide.
• A supported Nissan or Infiniti with a healthy battery.
• VQLab. Backing up works in the free Lite edition.

Step 1: install the cable

Plug the cable into the laptop. Windows usually installs the CH340 driver by itself; if it doesn't, install it from wch-ic.com. In Device Manager, under Ports (COM & LPT), the cable shows up as a COM port.

Step 2: connect to the car

Plug the cable into the OBD2 socket under the dash. Turn the ignition on, but don't start the engine.

Step 3: read the ECU

Open VQLab, click Car on the toolbar, then Back up ECU. VQLab finds the cable, connects, checks your ECU's software ID and reads the whole ECU. When it says Backup saved. You can turn the ignition off., you're done.

Step 4: keep it safe

The backup is saved in Documents\VQLab\Backups. Copy it somewhere else as well, like a USB stick or cloud storage. It's the one file that can always put your car back to stock.

What you can do with the backup

Open it in VQLab to look through every map your ECU uses: ignition timing, fuel, limiters and more. VQLab tells you whether your ECU is supported and what it found. When you want to change maps and flash them, that's VQLab Pro.

If it doesn't connect

• Check the cable is in both ends and the ignition is on.
• Check Device Manager shows the cable as a COM port (install the CH340 driver if not).
• Make sure it's a CH340 cable. ELM327 "OBD scanners" and Bluetooth dongles can't read the ECU.