Best OBD2 Scanner for HHO Owners in 2025: Top 5 Picks

What HHO Owners Need from a Scanner

A generic code reader that just reads and clears CEL codes isn't enough for HHO tuning. You need: live fuel trim data (STFT and LTFT), O2 sensor voltage streaming, real-time MPG calculation, and ideally the ability to log data over time. These five scanners deliver all of that.

#1: ScanGauge II — Best Dashboard Display

The ScanGauge II mounts to your dash and displays 4 live parameters simultaneously. Set it to show STFT, LTFT, instant MPG, and O2 voltage — your complete HHO tuning dashboard at a glance. $149, plug-and-play, no phone required.

#2: BlueDriver Bluetooth — Best Phone Integration

The BlueDriver app on iOS/Android displays all OBD-II parameters with graphing, logging, and professional-grade freeze frame analysis. Excellent for documenting LTFT trends over time. $100 adapter + free app.

#3: OBDLink MX+ — Best Protocol Support

Fastest response time of any Bluetooth OBD adapter, supporting manufacturer-specific PIDs that can unlock additional parameters beyond standard OBD-II. Pairs with multiple apps. $100.

#4: FOXWELL NT301 — Best Budget Wired

For HHO owners who want a standalone unit without phone dependency at a lower price point. Displays live O2 sensor data and fuel trims clearly. $50.

#5: Ultragauge MX — Best Trip Computer

More parameters than ScanGauge, color display, and extensive customization. Shows fuel cost per mile, historical MPG graphs, and acceleration timing. $90.