LAMBDA SENSOR BOSCH LSU 4.9 LONG WIREThe Bosch LSU 4. 9 wideband lambda sensor (part number 258017025) is the go to solution when you need precise air fuel ratio readings for serious tuning or motorsport use. This is not your average narrowband O2 sensor it reads across a broad lambda range (from around 0. 65 all the way to free air), giving you accurate data you can actually trust when dialing in your setup. It runs a monotonic output signal that works perfectly in closed loop systems,