The Trouble With Diagnosing Emissions Systems

For a few years now a number of vehicle emissions testing programs in the U. S. have been conducting a new type of emissions test on OBD II-compliant vehicles, nicknamed a “Plug & Play” test. This test does not directly measure the vehicle’s emissions. Instead, the technician at the test centre plugs into the OBD II data link connector (DLC) and scans the information available there. If the malfunction indicator light (MIL) is on or if any diagnostic trouble codes (DTCs) are stored in the PCM’s memory, the vehicle fails the emissions test right off the bat.

According to Counter Point, a seasonal newsletter produced by Wells Manufacturing Inc., it states the following:

“If no DTCs are stored, testing moves to the next level. The technician at the test centre uses his test equipment to retrieve information about the vehicle’s OBD II monitors — specifically to see how many are reporting as ‘Ready.’ In many cases, if more than two monitors report as ‘Not Ready,’ the vehicle will be deemed not ready for further testing. Newer vehicles may fail if even one monitor is reporting ‘Not Ready.’ The vehicle owner can’t re-register the vehicle until the reason is found and repaired.”

“The way a code works is that it’s either pending, current or it’s history,” adds Ben Johnson, product line director for North America service product development and sales for Delphi Corporation, “And even if it’s history it would not be a far reach to say that the

EPA would say, ‘Well, it’s history because it happened, but as far as we’re concerned unless it’s cleared it may reoccur’. So I can see where they might not consider that a healthy vehicle.”

Now whether or not this remains an issue when it comes to emissions testing for Ontario’s Drive Clean program or British Columbia’s AirCare program is uncertain; but just the fact that it’s a possibility makes this piece of information a worthy tidbit for upcoming repairs.

Reflashers & the Modern Tune-up

Back in the early-90s, the government’s logic was if they could mandate the amount of monitoring systems in cars, they could also pull out the necessary information related to emissions and emissions control. Thus OBD II came into being and since the mid-90s has been the standard for on-board diagnostic testing. However, a vehicle’s ECM is a whole different story altogether.

For the past four years, Delphi Corporation has been selling its Universal Reflash Tool for the purpose of keeping a vehicle’s ECM updated with the latest calibration available from the car’s manufacturer. There are advantages to making reflashing part of your daily maintenance repertoire, even with the training that will be involved to do it right.

“Technicians definitely need good training if they wish to undertake the reflashing task. Training isn’t the only requirement. They need reliable equipment (J2534 device and PC), a stable Internet access connection (high-speed Internet preferred), and a stable DC power supply,” says Chuck Gonwa, senior product manager of the Bosch Group for diagnostics business unit. “With all these requirements at hand, the technician is more likely to perform a correct reflash procedure without damaging or destroying the vehicle ECU,” Gonwa indicated.

For Bosch, the reflash market lies in its Flasher Pro, a universal style J2534 vehicle interface box that cover all makes, models, and reflashing protocols, and covers Ford, GM, Chrysler, and Imports.

“It literally is affecting the control systems for every control system on the vehicle. With a reflash they can adjust how much EGR pressure is applied, whether there’s a [more efficient] RPM and load, how the MAF sensors should be interpreted, it’s kind of a balance between emissions control and performance,” says Malcolm Sissmore, general manager for Canadian aftermarket and country director for Delphi.

While this might be true, Delphi’s Johnson notes that shops are a very reactive environment. If a guy brings in his car to a shop with an oil leak, a technician will do everything to solve that oil leak, but may not notice his windshield is cracked, or that his headlights don’t work unless they’re a very proactive shop.

“The reflash checks are really a part of the modern tune-up,” continues Johnson, “Whatever you’re in that vehicle for you should at least look to see what’s available (update-wise) because (a) it may solve a problem for the purpose of what the vehicle was originally brought in for and (b) it may also identify things the customer might not have known about.”

He also notes that reflashing is a good proactive course for a shop owner since it has the potential to increase the revenue count without increasing the car count. Not bad for the two minutes it takes to diagnose with the reflasher tool.

The Oxygen Sensors

While oxygen sensors are a very reliable component in the emissions system, even so they can difficult to diagnose for both the technician and the consumer, even from a head-on visual inspection. An oxygen sensor might have heavy black deposits on it and while it might appear damaged at first glance, it is more likely it’s a sign of normal wear from years of regular operation.

“Oxygen sensors have gotten better, but they are in a tough environment being in an exhaust,” says Mark J. Hicks, technical service manager for Wells Manufacturing Inc. “And what happens a lot of the time today with oxygen sensors is they’re all heated since OBD-II and a lot of times the heaters go out.”

Delphi recently released its line of planar oxygen sensors which feature a patented protective sensor coating increasing its resistance to contaminants such as silicone, phosphorous and other fuel/oil additives. A unique multi-layer construction, made of zirconia and alumina, also makes Delphi’s sensor elements stronger and more resilient to thermal shocks and engine vibration.

“Oxygen sensors today are durable and reliable for thousands of hours of driving, but can be damaged when contaminated by excessively rich fuel, oil or additives in the fuel, some sealants around the engine, occasionally made inoperative by thermal shock, or simply worn out after immersion is hot exhaust gases for tens of thousands of miles. Spark plugs can suffer from an eroded center and ground electrodes which effectively widens the spark gap, fouled by excessive oil consumption and over time suffer carbon buildup which can cause misfire or less performance,” said Al Krenz, director of service for the Bosch Group.

O2 sensors are also a very fickle component in the sense that it’s very easy to blame a misdiagnosis on the sensor when another problem is running a bad fuel mix or a leak somewhere else.

“The oxygen sensor can only compensate for so much if there are other issues with the fuel/emissions systems. If you have a lean condition in the vehicle, the oxygen sensor will tell the ECU that a lean condition exists and the ECU will consequently enrich the mixture, but the vehicle will continue to run lean,” says Chris Harrison, product manager for NGK Spark Plugs Canada, “While the code that’s going to come out is for the oxygen sensor, replacing that oxygen sensor will not solve the inherent issue.”

“You can have a vacuum leak, for example, and you see this typically where it works the other way; technicians may incorrectly blame the oxygen sensor. The ECU will store a fault code that may be specific to the oxygen sensor and unfortunately the problem with today’s diagnostics I think is people rely on [scan tools] so much so that whatever that code is they immediately say that is the problem and decide they must replace that part. Then it becomes a game of ‘What now?’”

While O2 sensors bear the brunt of the exhaust, be aware that when diagnosing emissions systems that inaccurate readings might the symptom of a different problem altogether.

Spark Plugs

The problems with spark plugs are more apparent to the consumer if one is dam
aged or extremely worn — poor throttle, hesitation when hitting the gas, hard starts (especially in winter) — when compared to a lower fuel economy with a damaged 02 sensor which is harder for the consumer to detect immediately.

Similar to the example of vacuum leaks damaging O2 sensors, it’s possible a leak can occur involving spark plugs but from an entirely unrelated system.

“A spark plug well can fill up with water from either condensation, wash in the engine, or A/C compressor tubes that drip water into a certain cylinder or tube and fill it up. They’ve also found instances where the seal in the back of a hood can be defective and leak rain,” says Hicks.

The latest development in OE spark plug technology is what NGK calls Double Fine Electrodes (DFE). “What we’ve done now is basically laser welded a fine electrode on the ground, so it’s two fine electrodes pointing at each other. And what that does is provides more room for greater flame front propagation,” says Jeff Desveaux, North American product manager for NGK Spark Plugs Canada. ” With better flame front propagation you get better ignitability.”

Without going too much into the knitty-gritty of spark plug diagnosis, other things to watch out for include checking for dark brown or black deposits (which may not be a sign that the spark plug is worn, but rather a sign that the spark plug has become fouled as a result of the engine) and gap growth (whereby the centre electrode rounds off making the electrode tougher for the spark to generate).

One issue that’s worth stressing is the need for consumers to come in for regular maintenance intervals with their car, as spark plugs only last for a certain amount of time. While the ‘Check Engine’ light will surely go off if there’s something wrong in the engine, this is a simple measure that can help, not only add revenue to your business, but also prevent problems before they occur if the spark plugs have passed their recommended allotment.

While this article doesn’t come close to covering all of the components that make up the emissions system (i. e. the catalytic converter, EGR valve, distributor cap, etc.) it never hurts to be reminded to the basics, especially when it comes to diagnosing these systems.

SSGM

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RefeRence List:

Delphi Corp. www.delphi.com

NGK Spark Plugs Canada www.ngk.com

Robert Bosch www.bosch.com

Wells Manufacturing Corp.