Engine & Performance
Exhaust, Catalytic Converters & Smog
A P0420 does not automatically mean a catalytic converter. An upstream leak or a lazy oxygen sensor will set the same code for a tenth of the price.
Signs you need this
- Catalyst efficiency below threshold codes
- Rattle from under the car that changes with engine speed
- Smog test failure or readiness monitors that will not set
- Sulphur or rotten-egg smell from the exhaust
How we approach it
We diagnose catalyst efficiency faults by comparing upstream and downstream sensor waveforms under controlled conditions, and we pressure test the exhaust for leaks before condemning anything. When a converter genuinely has failed we fit CARB-compliant units so the car passes California inspection. We also repair the flex pipes, resonators and rear boxes that rot out on coastal cars — and living in Huntington Beach, that is most of them.
What the job includes
- 01Upstream and downstream oxygen sensor waveform comparison
- 02Exhaust leak pressure testing and back-pressure measurement
- 03CARB-compliant catalytic converter supply and fitting
- 04Oxygen and air-fuel ratio sensor replacement
- 05Flex pipe, hanger and muffler repair
- 06Drive cycle to set readiness monitors before smog testing
Common questions
Will an aftermarket converter pass smog in California?
Only if it is CARB-approved for your specific application, which is what we fit. Cheap online converters without an EO number will fail a visual inspection.
My car failed smog. Can you fix it and get it retested?
We repair the cause and complete the drive cycle so the monitors are ready, then you take it back for the retest. We will tell you honestly beforehand what the repair is likely to cost.
Let us take a look at it.
Call and describe what the car is doing. We will give you an honest assessment before any work begins.
7492 Slater Ave, Huntington Beach, CA 92647 · Mon–Fri 8:00am–5:00pm
Related services
Engine Rebuild
Complete rebuilds to factory tolerances for M272, M273, M156, M271, M274 and more.
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Stretched chains, worn guides and failed tensioners — caught before they cost you an engine.
Balance Shaft & Idler Gear
The M272 and M273 gear wear issue — diagnosed by serial number, quoted honestly, fixed once.