Photo : Retired master technician Kris Lewis of the Automotive Training Group stressed homework and using new resources as a way for techs to keep up to date with changing vehicle technology.
Learning emissions control diagnostics.
Diagnosing the “catalytic converter” code for fun and profit, and no comebacks.
The 420 code comes up on your scan tool, with the data message, “converter efficiency below threshold.”
Does that mean your diagnosis is now complete, and it’s time to replace the catalytic converter? The short answer is “no.”
The longer (three hour) and thorough answer was recently presented to technicians attending the Walker Emissions Control Diagnostic Workshop, in Newmarket, Ontario, in October. It was one of 20 such seminars conducted in Canada by Tenneco’s Walker brand this year, to help technicians understand the tricky nature of emissions control diagnosis and repair.
“Replacing the catalytic converter doesn’t correct the root cause of the problem,” said Mark Potts, an Area Sales Manager at Tenneco. “The seminars focus on getting to the root of emissions control issues; what caused the converter efficiency code in the first place.”
Potts added that this enlightened approach means fewer catalytic converters (or CATs) get needlessly replaced, and fewer fail in the future. In other words, “fewer comebacks.”
Inputs critical to CAT performance
Conducting the Newmarket seminar — and all the others — was Kris Lewis of the Automotive Training Group. Potts noted Lewis is consistently rated very highly by attendees, and judging by the Newmarket seminar, it’s not hard to see why.
The straight talking Lewis hails from New Jersey, where he spent 38 years “in the bays,” honing his diagnostic skills and strategies. His seminar is a potent blend of overall philosophy on how techs must approach their craft in this day and age of electronics and changing technologies, and very specific emissions control diagnosis procedures, with numerous tips and tricks thrown in for good measure.
But he started his seminar with a brief chemical lesson on the combustion process, discussing what goes in, what happens during the process, and what intended and non-intended chemicals are now headed toward the catalytic converter.
“A catalytic converter doesn’t reduce those chemicals, it just re-arranges those chemicals,” said Lewis. So that was the first main point of the seminar: The converter is not designed as a trash receptacle to catch stuff when the engine is running poorly, but as a system for rearranging bad chemicals into good chemicals when the engine is running correctly and producing “intended” outputs.
“Anything else, and it won’t work as designed,” said Lewis. An incorrectly running engine also has the potential to ultimately destroy the converter.
New technology requires new diagnostic philosophy
Catalytic design is not overly complicated, and hasn’t changed much since they were first introduced in the 1970s. But two things have changed that’s transformed the technician’s relationship with them.
One is the rising cost of converters, driven by the rising prices of the precious metals needed for their construction. Lewis noted customers are becoming less and less tolerant of replacing converters. They are no longer a semi-disposable item, like a burned out headlamp. He cited the VW Touareg, whose replacement catalytic converters retail at the dealership level for about $4,500. Two, everything upstream of the converter, where technicians need to do
the majority of emissions control diagnosis, has changed.
“A car is nothing more than 50 or 60 computers on a set of wheels,” said Lewis. It’s a world where you need your scan tool just to replace the wipers and rotate the tires.
Therefore, one of the essential elements needed for learning to how to diagnose changing technology today is homework. “It’s back with a vengeance,” said Lewis, who added that it’s much more productive to sit in front of the computer after supper at home, than it is to try and squeeze in some learning time during a busy shop workday.
Lewis also noted that now that we’re “scanning for all codes”, it’s essential techs have familiarity with all those codes, and it looks like the only way to obtain that familiarity is through after-hours homework. The other essential element is technology itself — fight fire with fire. “You have to learn how to use technology to fix technology,” said Lewis.
He advocates that technicians have their own computer stations in the bay, so they‘re able to print out scan tool data (to see better), and to more quickly access diagnostic information that can only be obtained from Internet-based sources. He added that leveraging manufacturer-based websites for diagnosing has, or will, become imperative, and strongly advised techs to visit the website, natacanada.ca. The “OEM Website Matrix” button you will find there under the Training menu, will bring up all the OEM website links. OEMS are required by law to give emission-related diagnostic information to the aftermarket service industry.
The other big Internet resource is iatn.net,the website for the International Automotive Technicians Network. “Last time I looked there were 75,000 techs chatting on the forums,” said Lewis. “If you ever think you’re the only person that’s ever had a certain problem, you’ll soon see you’re not. It’s a phenomenal resource.”
Back to Basics
Lewis noted that many techs might feel apprehensive about the increasing number of computer-based systems in vehicles, but they shouldn’t… “No matter what they do in a car, now and in the future, one thing they can’t change is the basic law of electricity. If you can master that, it won’t matter if the car has 5 or 50 computers.”
In addition to mastering electricity, Lewis advised technicians get proficient again at using the Five-Gas Analyzer. “We need them more than ever,” noted Lewis. According to him, the best way to use the analyzer is in tandem with the Lambda Calculator. Those calculations covert the ratio of the various chemicals coming out of the exhaust, into their ratios going in. If the ratios “going in” are off, you know the car has an issue. As stated in the Walker Diagnostic Training Manual: “Unless you have another clear direction to go, you should perform a Lambda calculation on every emissions failure to be sure the mixture is correct.”
Concluded Lewis: “Five gas analyzers and Lambda were used for diagnosing by the auto industry way before there ever was a computer on this planet. I’ll say it to the day I die… The trick is to go back to basics. Five-gas analyzers and Lambda. Lab scopes. Basic electrically. Tell me what I can’t fix?”
Tips and Tricks
• Match the converter to the customer.Tenneco manufactures Walker EPA-compliant aftermarket converters as well as Walker CalCat converters for regions requiring the use of California Air Resources Board (CARB) compliant units. Tenneco also offers Walker Ultra EX converters for certain highly sensitive applications.
• Send a customer a questionnaire by email, for critical personal driving and vehicle history.
• Road test each vehicle.
• Flushing the coolant system is no longer an up-sell; it’s required to keep back cylinders clean.
• Take pictures of dented converters when customer vehicles are in for other repairs.
• Engine management issues can result in converter failure before specific codes come up.
How Catalytic Converters Prematurely Expire
• Poisoning by leaded gas or silicon.
• Accumulation of exhaust deposits. Converters that don’t reach operating temperatures often enough, don’t burn these deposits off.
• Overheating inside the converter. Many causes, but fuel control issues is a leading one.
• Thermal shock. Driving over asnow bank?
• Structural damage.
Wrote by: MIKE GOETZ