A failed smog check tells you which part of the emissions system is out of range. The right response is diagnosis, then a targeted repair, then a retest. This guide covers the common causes and your options for help with cost.
Key takeaways
- The failure report points to the system, not the part.
- Diagnose before you buy parts.
- State assistance may help eligible owners.
Read the failure report
The report lists readings for hydrocarbons, carbon monoxide and nitrogen oxides, or a failed monitor, visible or functional check. Each points to a different set of causes. Keep it. Our first-steps guide shows what to do before the car goes back on the road.
The check engine light
A lit light fails the test and is its own diagnosis problem. See our guide to the check engine light and smog.
The usual suspects
Catalytic converter wear, oxygen sensors, evaporative leaks and EGR problems cause most failures. Each has its own page: catalytic converters, oxygen sensors, evap leaks and EGR valves.
Readiness monitors
A not-ready result after a battery change is not a failure of the equipment. Our monitors guide explains the drive cycle.
Help with cost
California's Consumer Assistance Program may help eligible owners with repairs or vehicle retirement. Read our CAP guide.
After the repair
Retesting should confirm the fix. We cover timing in our retest guide. Peña's diagnoses, repairs and retests in the same shop.
Questions to ask a shop before you authorize a repair
Ask which test led to the diagnosis and what the failing reading was. Ask whether the repair addresses the cause or only the symptom. Ask whether the shop will retest and how long the retest window is. Ask for the estimate in writing. A shop that can show the data behind its recommendation is one you can trust, and one that cannot is guessing with your money.
In this guide
- Failed Smog Check in Bakersfield: What to Do First
- Check Engine Light and Smog Check: Why It Fails
- Catalytic Converter Failure Signs and Why It Fails Smog
- Oxygen Sensor Replacement: Smog Fixes in Bakersfield
- Evap Leak or Loose Gas Cap: A Cheap Smog Failure
- EGR Valve Problems and High NOx Smog Failures
- Smog Monitors Not Ready: Why and How to Fix
- Smog Repair Help in California: The Consumer Assistance Program
- Smog Retest After Repair: Timing and What to Expect
Need help in south Bakersfield?
Questions about smog repair? Read our Smog Repair page, call (661) 599-9098 or request a time. Peña's Auto Electric, Smog & Repair, 303 Taft Hwy, Suite B, Bakersfield, CA 93307. Mon to Fri 9:30 AM to 5:30 PM, Sat 8 AM to 1 PM.
Frequently asked questions
Can I retest right after repair?
Sometimes, if monitors are ready. Otherwise a drive cycle comes first.
Is every failure expensive?
No. Some are small fixes such as a gas cap or sensor.
Should I buy parts myself?
Diagnose first. Guessing wastes money.
Where do I start?
Bring the failure report to the shop.
Related reading
- Failed Smog Check in Bakersfield: What to Do First
- Check Engine Light and Smog Check: Why It Fails
- Catalytic Converter Failure Signs and Why It Fails Smog
- Oxygen Sensor Replacement: Smog Fixes in Bakersfield
- Evap Leak or Loose Gas Cap: A Cheap Smog Failure
- EGR Valve Problems and High NOx Smog Failures
- Smog Monitors Not Ready: Why and How to Fix
- Smog Repair Help in California: The Consumer Assistance Program
- Smog Retest After Repair: Timing and What to Expect
Sources
- California Bureau of Automotive Repair, Smog Check program and consumer information
- California Bureau of Automotive Repair, Consumer Assistance Program (repair assistance and vehicle retirement)