CEL bulb working or not, a blown bulb wouldnt prevent the car from running... i trust my code reader, it has pulled codes on the audi recently when the check engine light came on. it was just a random miss fire, but enough to prove that the code reader works. let alone i get live data from it, such as coolant temps, speed, throtle position and a bunch other. so we can stop doubting the scan tool. it worked before on the audi, its still working (on other cars), and is now powering on, but showing no data

 

This is all true. However, if the bulb is operational, but does not come on, AND the code reader will not talk with EITHER ECU, most likely they're both shot. This is what we're trying to explain.