OBD or Opacity? What Your Truck’s Year Decides About Clean Truck Check

Two trucks pull into the same yard for the same Clean Truck Check. One is done with a cable. The other needs a machine that costs as much as a used pickup. Same test on paper. Completely different job.

The thing that decides which one you get is your engine year. Here’s how to know before you drive anywhere.

The line is 2013

Engine year 2013 and newer: OBD test. Your truck has an on-board diagnostics port. The tester plugs in, pulls the emissions data your engine has already been recording, and submits it. Nothing gets revved. Nothing gets measured out the stack. The truck reports on itself.

Engine year 2012 and older: opacity test. No usable OBD port, so there is nothing to plug into. The only way to find out what is coming out of your truck is to measure what is coming out of your truck. That is the opacity test — sometimes called a smoke test.

Go by the engine year, not the year on the title. A 2014 truck with a rebuilt older engine follows the engine.

What an opacity test actually involves

A probe goes in the exhaust. The engine gets run up under load while a meter reads how much light the smoke blocks — that is what “opacity” means. Clear exhaust lets light through. Heavy soot does not.

It needs a calibrated opacity meter that gets checked against a known standard. That machine is the whole reason this is a different conversation.

Why some places quietly turn older trucks away

An OBD test needs a laptop and a cable. That is why so many mobile testers exist — the entire kit fits in a van, and one person can run it.

An opacity meter is a seven-thousand-dollar piece of equipment that has to be maintained and calibrated. Most mobile operations never buy one. It is not that they will not test your 2009 — it is that they cannot.

You have probably already met this. You call, you give the year, and suddenly they are booked, or they refer you somewhere, or the price changes. That is the meter, or the absence of one.

We run both. Plug-in for 2013 and newer, opacity for 2012 and older, same shop, same day.

Motorhomes and RVs — read this part twice

If you own a diesel motorhome, two things are usually true at once.

• It is probably old enough to need the opacity test. Motorhomes get kept, not traded. A rig from 2008 that has been babied in a barn is still a 2008 for testing purposes.
• A lot of owners do not know they are in the programme at all. People hear “Clean Truck Check” and picture semis. If your coach is a diesel over 14,000 pounds, it is the same programme and the same schedule.

And RV owners hit the equipment problem harder than anyone. You are calling around asking who can test a motorhome, and most of the people who answer only own a cable.

What it costs here

$75. Both tests. Same price.

We do not charge more for the opacity test even though it needs the expensive machine. One price is easier for you to plan around, and it is easier for us to stand behind.

Fail and the re-test is free. Sort out what is wrong, come back, we test it again at no charge. That matters more on older trucks, because they are the ones more likely to need a second run.

How often you need it

Twice a year for most vehicles in the programme. It is not a one-and-done — and DMV can hold your registration over a missed one, which is the part that catches people out. The compliance deadline does not care whether your truck is OBD or opacity. Both count the same.

The wider programme rules are covered in our Clean Truck Check guide.

Before you come in

Nothing complicated. A warmed-up engine reads truer than a cold one, so if you have been sitting, take it around the block. If your check-engine light is on, say so when you call — on an OBD truck that will usually fail the test outright, and it is better to know before you drive over. If soot is the problem, our DPF and DEF guide covers what is usually behind it.

Bring your registration. That is it.

Get it done

Gomez CARB Clean Truck Check — Bakersfield
4615 E Brundage Ln, Unit 7, Bakersfield, CA 93307
(661) 360-1717
Open 7 days. No appointment needed.

Semis, box trucks, service trucks, motorhomes and RVs. 2012 and older welcome — we have the meter.

Program details can change year to year — call us for the latest, or check CARB’s Clean Truck Check page.