---
title: "Piedra's Smog Test Only — Clean Truck Check, Walnut, CA"
description: "Piedra's Smog Test Only in Walnut, CA is on CARB's Clean Truck Check tester list with 2 credentialed testers. Offers mobile testing, OBD testing, smoke opacity…"
url: "https://ctcfinder.com/tester/piedras-smog-test-only-walnut/"
updated: "2026-11-01"
publisher: "CTC Finder (independent directory, not affiliated with CARB)"
---

# Piedra's Smog Test Only

Clean Truck Check tester in Walnut, CA (Los Angeles County).

> CTC Finder is an independent directory, not affiliated with CARB. Tester data: CARB Clean Truck Check public tester list, last checked November 1, 2026. Confirm services, hours and prices with the tester.

| Field | Value |
|---|---|
| Location | 19939 Valley Blvd, Walnut, CA 91789 |
| County | Los Angeles County |
| Phone | (909) 869-8056 |
| Mobile testing | Yes |
| OBD testing | Yes |
| Smoke opacity (non-OBD) | Yes |
| Motorhomes | Yes |
| Credentialed testers | 2 |
| Last verified | 2026-11-01 |

## Which trucks Piedra's Smog Test Only can test

| 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 | Yes |
| California-registered motorhome | Same test as above by engine year, once a year | Yes |

## Clean Truck Check testers in Los Angeles County

Piedra's Smog Test Only is one of 516 testing businesses in Los Angeles County on CARB's public tester list. 465 of them offer mobile testing and 190 do smoke opacity tests. In Walnut itself there are 3 listed businesses, 3 of them mobile.

## 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](https://ctcfinder.com/guide/deadlines-2026-2027/). You can test up to 90 days before a deadline. Free email reminders: https://ctcfinder.com/reminders/

## Frequently asked questions

### Does Piedra's Smog Test Only offer mobile Clean Truck Check testing?

Yes. Piedra's Smog Test Only 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 Piedra's Smog Test Only test a 2012 or older diesel truck?

Yes. Piedra's Smog Test Only lists smoke opacity testing, the test CARB requires for diesel trucks of model year 2012 and older (no OBD). See [OBD vs smoke opacity](https://ctcfinder.com/guide/obd-vs-smoke-opacity-test/).

### How much does Piedra's Smog Test Only charge for a Clean Truck Check?

Piedra's Smog Test Only has not published prices with us; call (909) 869-8056 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](https://ctcfinder.com/guide/cost/).

### Is Piedra's Smog Test Only a CARB-credentialed tester?

Piedra's Smog Test Only appears on CARB's public Clean Truck Check tester list with 2 credentialed testers, 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 nearby

- **[Walnut Smog Center](https://ctcfinder.com/tester/walnut-smog-center-walnut/)** — 319 Lemon Creek Dr Ste L, Walnut, CA 91789 — (626) 202-2827 — 1 mi. Services: mobile testing, OBD testing, motorhome testing.
- **[Walnut Smog Check Center](https://ctcfinder.com/tester/walnut-smog-check-center-walnut/)** — 319 Lemon Creek Dr Suite L, Walnut, CA 91789 — (909) 594-1913 — 1 mi. Services: mobile testing, OBD testing, motorhome testing.
- **[California CARB Check](https://ctcfinder.com/tester/california-carb-check-west-covina/)** — 2329 E Regina St, West Covina, CA 91792 — (626) 736-7797 — 3 mi. Services: mobile testing, OBD testing.
- **[Joseph Avila-Castro](https://ctcfinder.com/tester/joseph-avila-castro-west-covina/)** — West Covina, CA 91792 — (626) 383-3036 — 3 mi. Services: mobile testing, OBD testing, smoke opacity (non-OBD) testing.
- **[Fridda Vanegas Cabrera](https://ctcfinder.com/tester/fridda-vanegas-cabrera-diamond-bar/)** — Diamond Bar, CA 91765 — (626) 588-7416 — 3 mi. Services: mobile testing, OBD testing.
- **[Fleet Cert](https://ctcfinder.com/tester/fleet-cert-west-covina/)** — 521 South Lark Ellen Avenue, West Covina, CA 91791 — (626) 610-8533 — 4 mi. Services: mobile testing, OBD testing, smoke opacity (non-OBD) testing, motorhome testing.