CA Diesel Emissions Testing

Testing Procedures & Regulations


California Diesel Emissions Inspection

Effective January 1st, 2010, light duty diesel vehicles model year 1998 and newer are required to undergo diesel emissions inspections - yes, you have to SMOG your diesels in CA. Similar inspections are also required in Nevada, New York, & Colorado, while other forms of inspection are required in additional states as well. Liight duty diesels are classified as a diesel powered vehicle with a gross vehicle weight rating (GVWR) below 14,000 lbs. Vehicles with a GVWR above 14,000 lbs are exempt from the testing requirements. In this 3 step emissions inspection, the procedures are:

1. Visual inspection of the engine's emissions control equipment.
2. An OBDII (on board diagnostics system) check.
3. A visible smoke test from the tailpipe and crankcase.


CA Diesel SMOG Smoke Test Procedures, as outlined by the California Bureau of Automotive Repair:

1. Idle Smoke Test: The tailpipe emissions are observed with the vehicle idling for 10 seconds.
2. Crankcase Smoke Test: The crankcase is observed for smoke for 10 seconds at idle.
3. BAR Snap Test: The will be quickly accelerated between 2,000 - 3,000 rpm. Using the side mirror(s), a technician will watch for excessive exhaust soot. The throttle will be snapped 3 times, with 3 second pauses between snaps. The first snap does not count, meaning any visible smoke that is emitted on the 1st snap will not conclude in a failure of the test. Any smoke plume that appears 5-15 feet from the tailpipe and lingers for more than 3 seconds on the 2nd or 3rd snap will result in a failure of the test.


Visual Inspection:

During the visual inspection, technicians will be looking to ensure that all factory emissions equipment is in tact. This includes, but is not limited to, positive crankcase ventilation (PCV), crankcase depression regulator (CDR), catalytic converters, diesel oxidation catalysts (DOC), diesel particulate filters (DPF), selective catalytic reduction (SCR), and exhaust gas recirculation (EGR) systems. They will also be looking for aftermarket components such as exhaust systems, air intakes, etc.


Modifications that DO NOT require a CARB Executive Order (will not result in failed inspection):

- Air horns (intake elbows).
- Modifications to air cleaner assemblies (cold air intakes, aftermarket filters).
- Exhaust system modifications made AFTER the last emissions control device.
- Auxiliary/aftermarket fuel filters or fuel-water separators.
- Aftermarket lift pumps & auxiliary fuel tanks.
- Water injection systems.


Modifications that DO require a CARB Executive Order (you will be failed without one):

- Turbocharger modifications or aftermarket turbos.
- Aftermarket intercoolers.
- Modified or aftermarket injectors or injection pump(s).
- Propane, methanol, hydrogen, or nitrous oxide injection.
- Aftermarket exhaust gas aftertreatment controls (DPF, DOC, etc.).
- EGR/EGR cooler modifications.


The Problem With Diesel Emission Testing:

The problem with diesel emissions testing in CA is that the technicians are not formally trained. They are used to inspecting gas powered cars/trucks and any shop that does so now has the ability to inspect diesels, even with minimal knowledge of them. When diesels get some miles on them, it is common for them to produce some visual exhaust soot. We worry that the technicians lack of experience with diesels will make them unfit to judge whether soot is the result of modifications, or a just a well worn truck. Testing Experience:

We had to get our 2003 6.0L Power Stroke tested recently. The procedure was painless, and took all of 5 minutes. The truck passed with flying colors, even though it's been known to blow a light haze of smoke with the 200,000 miles we have on our motor. With heavy throttle inputs, this truck smoked from the moment it left the show room floor, so we had some concerns. Unfortunately, while at our local smog shop we had the misfortune of witnessing another Super Duty fail. The owner, an older gentleman, also had a 6.0L Power Stroke. The truck, which he claimed had never been tampered with, blew a gentle haze of soot on the 2nd and 3rd throttle snaps. The technicians did not provide him with any useful advice as to how to get his truck fixed, other than to take it to the dealership. As we said before, even a stock diesel can blow a little smoke, especially when you mash down on the throttle and the turbo is not spooled. Another truck we witnessed fail was a 2003-2005 Dodge Ram with the 5.9L Cummins diesel. The owner had smoke stacks coming out of the bed of the truck, so the technicians refused to proceed with the inspection. According to the owner, all emissions components were still intact and the truck had not received any further modifications. We consider this an injustice, because the Bureau of Automotive Repair clearly stated that exhaust modifications performed downstream from the emissions equipment is not grounds for a failure. While we understand the need for inspecting diesels, we're disappointed in the how the system has been implemented.

















































































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