TX inspection rejection guide · Glass Box Diagnostics
In the counties that add an emissions test to the safety inspection, the analyzer measures HC, CO and NOx at two speeds and the result either passes or it doesn't. High numbers feel like an environmental mystery, but they map to a short list of engine conditions: unburned fuel (a misfire, a stuck injector, a chronic rich trim), a converter that isn't doing its job (often because something upstream is killing it), or air leaking in and throwing every calculation off. The analyzer's failure pattern points at which family to test first.
The clock: Same clock as a light-on failure — the rejection slip states your repair window, and re-testing before the underlying fault is confirmed just costs you a second line at the station. One diagnostic visit beats three failed re-tests.
A $2,400 cat quote off the analyzer printout alone — while the injector causing it stays in place and the OBD check still fails on monitors. Aftermarket converters then fail the next test for the wrong compound.
Typical guess-and-swap cost: $1,200–$2,800 (converter swap) when the real fault was a $60 sensor, hose, or injector
Live data from cold start: fuel trims, front-vs-rear O2 waveforms, per-cylinder misfire counters, injector balance, fuel pressure, then a smoke test. If the converter really is done, the data proves WHY — and that's what makes the repair last.
We come to you — Canyon Lake, San Antonio & Austin. Written report naming the root cause — see a sample. Already have a repair quote? Run it through the numbers.