Just over a year has passed since the OBD-II mandate came in, and while testing facilities are now comfortable with the new onboard diagnostic system test, technicians are still seeing a lot of readiness issues.
“The most common things we see are that the newer cars are failing, because the check engine light is on. We also have a lot of cars coming in that are not ready for testing because the battery went dead, or someone has cleared the check-engine light, and the car has not been through a proper drive cycle to qualify for testing. Those are the two biggest issues we see,” says Mitch Beck of Beck’s Auto in Toronto.
The Drive Clean test uses the vehicle’s onboard computer to identify emission problems. During the test, the information stored in the onboard computer is checked to determine if the emissions systems are working properly and are not releasing pollutants beyond the vehicle’s emission standards.
“Most of what we get calls about are the EVAP systems,” explains Will Carcone, trainer for CARS OnDemand. “The biggest thing is not knowing to take the time to do the correct drive cycle. The generic drive cycles don’t always work, so you have to refer to the specific drive cycle that the manufacturer has set out for that particular vehicle. Vehicles often come in with the codes cleared, but haven’t done the appropriate amount of driving for the necessary cycle of events to occur,” explains Carcone.
Some shops are seeing check-engine lights for items that appear to be unrelated to the emissions testing, when in fact they are related.
“In some cases we will get a check-engine light for a transmission problem or for an A/C problem that seems to be unrelated to the emissions, so we are unable to complete the test,” explains MD Shahin Miah of Mak Auto Service, in Scarborough, Ont.
“The transmission codes could interfere because they can be deemed as an emissions-causing issue,” explains Carcone. “If the vehicle is not shifting correctly, it won’t allow the engine to work efficiently, and that can change the tailpipe emissions and could cause a test failure. If you have an engine that is slipping, you’re going to have the engine revving too high and that’s going to cause more misses out the tail pipe, so that’s why they get flagged.”
A/C codes can also be deemed that way, because some vehicles will increase idle RPM, which in turn can cause an enrichment problem or a lean problem that creates higher NOX – and the enrichment situation could cause higher HCs.
“Anything that’s going to change the final fuel ratio, or any situation that may cause the vehicle to create more emissions, will cause the vehicle to fail. These issues can be challenging to troubleshoot if they are deemed as a non-emission issue when technically, in the computer’s mind, it does affect the drivability of the vehicle. Anything that might cause a drivability issue will cause a failure,” explains Carcone.
Under the Drive Clean program, regulated vehicles from model year 1998 to 2000 inclusive will fail if three or more monitors are set as “Not Ready,” while model year 2001 and newer vehicles will fail when two or more monitors are reported as “Not Ready.”
One reason some vehicles cannot complete the test is when the onboard diagnostic (OBD-II) system readiness monitors are not set. The fact that readiness monitors won’t set does not necessarily mean there is a malfunction.
Under certain conditions, even when a vehicle is not suffering from a malfunction, some readiness monitors will not run. When it is particularly cold, for example, an EVAP monitor will not run, as it often requires that the outside temperature be between 4 Celsius and 30 Celsius and the fuel tank between 15% and 85%.
Often, a situation where readiness monitors are not running can be caused by erasing the memory from the OBD system, either by clearing any diagnostic trouble codes or disconnecting the battery. Either of these strategies can often be employed by consumers armed with a scan tool or a wrench, thinking that no MIL light means no problem.
A professional technician may employ a similar strategy as a quick check of the validity of a diagnostic trouble code, but in both cases it requires that the readiness monitors be reset (either naturally through daily driving, or more quickly by using a drive-cycle reset procedure).
The best advice you can give your trade customers is to leave the DTCs in place and the MIL light lit, perform their diagnostics and repairs, and then perform the drive cycle procedures to spur the readiness monitors to completion. However, you should be aware of the fact that, depending on the repair, on many vehicles if you do not clear codes or reset the engine computer, the flags will not switch from not ready to ready.
It sounds simple enough, but in the real world getting those monitors to run properly can be a source of frustration for technicians. At the very least, it can be a time-consuming procedure that many shops still struggle to charge for.
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