What to know — Diesel smog rules in California
What does a diesel smog check involve in California? 1998 and newer diesel vehicles at or under 14,000 lbs GVWR require California smog inspection using OBD-II scan plus a visual check of all emissions control equipment.
- Diesel Particulate Filter (DPF) must be present and unmodified — removal is an automatic fail on visual inspection and OBD.
- Exhaust Gas Recirculation (EGR) system must be intact; deleted EGR triggers fault codes and visible fail.
- Diesel Exhaust Fluid (DEF) system on 2010+ diesel vehicles must be functional; limp-mode from DEF faults equals automatic fail.
- Opacity (visible smoke) test is performed — excessive black or blue smoke is grounds for rejection.
- Aftermarket tuners that alter emissions calibration are prohibited; OBD scan reveals tuner presence.
- Deleted emissions equipment can be restored before testing — some test+repair shops offer OEM restoration.
Per BAR diesel inspection criteria and CARB diesel emission control device rules.
About Diesel Smog Check at APEX Smog Check 2
Specialized diesel smog check performed at APEX Smog Check 2, our Temecula location.
Visit us for diesel smog check
- Address: 41892 Enterprise Cir S Suite C, Temecula, CA 92590
- Phone: (951) 296-3040
- Website: https://temeculasmogcheck.com/
- Hours: Mon-Fri 8 AM – 6 PM · Sat 8 AM – 4 PM
What we do
- California-required smog inspection
- OBD-II readiness verification
- Same-day electronic DMV certificate filing
- Walk-ins welcome (no appointment needed)
- Bilingual English / Spanish service
*Regenerated 2026-05-25 from GBP-verified canonical data.*