William Brown
Clean Truck Check tester in Sonora, CA (Tuolumne County).
- Mobile testing
- OBD test
- Motorhomes
William Brown appears on CARB's public list of credentialed Clean Truck Check testers. It lists mobile testing, OBD testing, motorhome testing. Mobile testing means the tester can come to your yard or job site.
- Location
- Sonora, CA 95370
- County
- Tuolumne County
- Phone
- (209) 540-7887
- Mobile testing
- Yes — comes to your yard
- OBD testing
- Yes
- Smoke opacity (non-OBD)
- No
- Motorhomes
- Yes
- Credentialed testers
- 1
- Last verified
Call (209) 540-7887 Open in Google Maps
The street address is not published for this listing (mobile or home-based tester). Call to arrange the test.
Before you call
- Have your VIN, odometer reading and plate number ready.
- Your vehicle must be registered in CTC-VIS and the annual compliance fee paid; the tester submits the result to CARB.
- Ask for the price per vehicle and any mobile trip fee. Typical published prices for an OBD test are $50–$135 per vehicle (see cost guide).
Which trucks William Brown can test
The test CARB requires depends on the engine's fuel and model year. Based on the services William Brown lists on CARB's tester list:
| Your vehicle | Test required | This tester |
|---|---|---|
| Diesel, model year 2013 or newer | OBD scan | Yes |
| Alternative fuel (natural gas, propane), 2018 or newer | OBD scan | Yes |
| Diesel, model year 2012 or older (no OBD) | Smoke opacity test (SAE J1667) plus visual inspection | Not listed |
| California-registered motorhome | Same test as above by engine year, once a year | Yes |
For a 2012 or older diesel, the nearest listed tester with smoke opacity testing is Sundborgs Repair Service in Sonora, about 1 mile away. See listing.
Clean Truck Check testers in Tuolumne County
William Brown is one of 5 testing businesses in Tuolumne County on CARB's public tester list. 4 of them offer mobile testing and 1 do smoke opacity tests. In Sonora itself there are 5 listed businesses, 4 of them mobile. All testers in Tuolumne County.
When your truck is due
Most trucks test twice a year, on a schedule tied to the DMV registration expiration date. CARB says OBD trucks move to four tests a year beginning October 2027. California-registered (non-commercial) motorhomes and agricultural vehicles test once a year. See the deadline guide. You can test up to 90 days before a deadline. Get a free email reminder before each one.
How to check a tester's credential
CARB publishes its Clean Truck Check tester list, where William Brown appears as of November 1, 2026. Listing there is optional, so a missing name does not always mean a tester is not credentialed. After the test, check that the passing result shows for your vehicle in CTC-VIS; that is what counts for compliance.
Frequently asked questions
Does William Brown offer mobile Clean Truck Check testing?
Yes. William Brown says on CARB's tester list that it offers mobile testing, so it can come to your yard or job site. Ask about a trip fee when you call.
Can William Brown test a 2012 or older diesel truck?
William Brown does not list smoke opacity testing, which older non-OBD diesel trucks need. The nearest listed tester that does is Sundborgs Repair Service (about 1 mile). Trucks from 2013 on get an OBD scan instead.
How much does William Brown charge for a Clean Truck Check?
William Brown has not published prices with us; call (209) 540-7887 for a quote. Published California prices are usually $50–$135 per vehicle for an OBD test and $190–$200 for a smoke opacity test, plus CARB's annual fee ($32.13 in 2026). See the cost guide.
Is William Brown a CARB-credentialed tester?
William Brown appears on CARB's public Clean Truck Check tester list, last checked November 1, 2026. Only credentialed testers can submit results to CARB; after the test, confirm the passing result shows for your vehicle in CTC-VIS.
Other testers near Sonora
-
Auto Tech and Tires
- Mobile testing
- OBD test
- Motorhomes
-
Brooke’s Mobile Truck Check
- Mobile testing
- OBD test
- Motorhomes
-
Sundborgs Repair Service
- OBD test
- Smoke opacity
- Motorhomes
-
TES
- Mobile testing
- OBD test
- Motorhomes
-
A1clean Check
- Mobile testing
- OBD test
- Motorhomes
-
Rorys Fire Apparatus & Diesel Repair
- Mobile testing
- OBD test
- Motorhomes
Source: CARB's public Clean Truck Check tester list, last checked . Listing on CARB's list is optional for testers, so some credentialed testers are not shown. Services, hours and prices change; please confirm with the tester before you go. Something wrong? Send a correction.