湿度传感器产品说明书

Ready Now?
We’ve had a state EPA-administered vehicle emissions inspection program here in Ohio for the past several years. Several counties within the state, including the county where our shop is located, have been targeted for special vehi-cle testing procedures, due to their “nonattain-ment” status.
At the beginning of this year, our state EPA began testing 1996 and later OBD II-compli-ant vehicles using a “plug-and-play” test. The technician at the testing center plugs into the vehicle’s data link connector (DLC), then checks for stored diagnostic trouble codes (DTCs). He also checks to see whether the OBD II Readiness Monitors have run to com-pletion and are flagged as “Ready” or “Com-plete.” If the Check Engine light is on, the ve-hicle cannot pass. And if the Readiness Moni-tors haven’t run to completion, the vehicle gets
a conventional tailpipe emis-sions test.
Since the new testing p r o c e d u r e s went into ef-fect, we’ve been seeing a lot of vehicles that have failed the test because one or more of the Readiness Monitors have reported “Not Ready” or “In-complete.” I u n d e r s t a n d there are many different time frames and special driving p r o c e d u r e s that must be
followed to get these monitors to report
“Ready” so our customers can pass their emis-sions tests. Some of them involve some pretty bizarre sequences, like accelerating from 0 to 30, then coming to a complete stop. (Ever try that one in traffic?) Is there an easier and quicker way to ready these vehicles? Also,how do we charge a customer for a service that we once offered for free? We have consid-ered discontinuing emissions-related repairs due to these new testing changes, but this would certainly hurt our business.
John Krouse Concord, OH Federal regulations required Ohio to implement the new OBD II test you’ve described. Extensive field research has already been conducted, and it’s been determined that the OBD II systems on these newer vehicles do a very good job of de-tecting emissions control system problems before they cause costly damage and allow harmful pol-lutants into the air. When a vehicle fails a plug-and-play emissions test, its OBD II system issues specific diagnostic codes and other information that can help a tech pinpoint the problem and make quicker, more effective repairs. OBD II in-spections also can be administered more quickly than the previous emissions tests.
It all sounds pretty great, doesn’t it? What your shop needs is a strategy to deal with cars that have failed the new test.
There are two general monitor classifica-tions—continuous and noncontinuous. Continu-ous monitors run all the time. Noncontinuous monitors may run only once per drive cycle.When a vehicle comes in with a DTC relative to a continuous monitor, don’t erase it. For some reason, the first thing many techs want to do is turn off the Check Engine light and clear the stored DTCs. This is the wrong approach for a number of reasons.
Fix the problem and drive the vehicle to en-sure the light remains out. If you’ve performed a code erase procedure either before or after re-
Trouble
Shooter
Karl Seyfert
Repairing an emissions failure is no longer enough. Changes in testing procedures mean it’s also necessary to return the vehicle properly prepped and ready to pass the retest.
On 1996 and later OBD II-compliant vehicles, the
PCM does a very good job of spotting problems that
could increase emissions to an unsafe level. Some
emissions testing programs now are tapping into this information to verify vehicle compliance.8
June 2004
P h o t o : K a r l S e y f e r t
pairs were completed, you’ve also reset all of the monitors to “Not Ready” or “Incomplete.” The car must now be driven until all of the required monitors have run. Even if you’ve been properly trained and have the needed drive cycle information, this adds to your repair time. And if you don’t have the drive cycle information, you could be driving around for days before the vehicle runs all the needed monitors to completion and is ready to pass a retest. That means wasted time and money.
Don’t worry about the original DTC.If you’ve successfully repaired the origi-nal problem that caused the vehicle to fail the first OBD II test, the DTC will remain in the PCM’s memory as a his-tory code for about 60 warm-up cycles before it’s erased. The MIL will not be on or commanded on during the retest.And as long as the vehicle meets other test requirements (monitors complete),the vehicle should pass the retest.
A different approach is required if a DTC was set when a noncontinuous monitor was run. Diagnose and repair the problem, then drive the vehicle at the same speed, load, temperature and rpm that were recorded in freeze frame data when the original DTC set. It may be necessary to repeat the drive cycle three or more times, but the PCM should eventually shut off the MIL and the vehi-cle will be ready to pass the retest.
Once again, you can see the advan-tage of not erasing the DTCs and reset-ting the monitors to “Incomplete.”With good drive cycle information, it will be necessary to run only the small part of the drive cycle that involves the original DTCs. If you erase the DTCs,you’ll have to extend the drive cycle or possibly drive the vehicle several times before all the monitors will have a chance to run.
Although it may be tempting, don’t rely on the customer to try to run the drive cycle and complete the monitors for you. Without the necessary drive cy-cle information, he may never drive the vehicle in the manner required to run all of the required monitors. By con-trast, a properly trained repair techni-cian can run the monitors to comple-tion in as little as 10 minutes and in a distance of two miles. Your goal should be to make the proper repair, then send the failed vehicle back for a retest with
all the monitors run.
If you’re doing performance work,you need drive cycle information, re-gardless of your state emissions re-quirements. The M OTOR OBD II Drive Cycle Guide is an excellent source for this information. It details the exact procedures you’ll need to follow and the driving conditions that must be sat-isfied to get the required monitors to run to completion. Procedures and conditions vary from manufacturer to manufacturer, and even among differ-ent models from the same manufactur-er. Without this information at your dis-posal, getting the job done is a hit-or-miss proposition at best.
Customer education, as well as addi-tional technician training, may be re-quired regarding these types of repairs.Your customer needs to understand the steps your shop must take to ensure that his vehicle will pass a retest. Be-fore you begin an OBD II repair, check the monitor status. This will ensure that your shop allots enough time (in-cluding road tests) to handle the job.Refer to Sam Bell’s “How Not to Get MIL-Stoned” in the April 2004 issue of M OTOR for OBD II customer relations help. And if you’d like to learn more about Ohio’s E-Check program, refer to . Information about available OBD II technician training opportunities can also be found there.。