Auto Service World
Feature   February 1, 2013   by Steve Pawlett

CounterTalk: Drive Clean, Emissions Controls, and OBD-II

As of January 1, Ontario’s Drive Clean vehicle emissions testing program began using onboard diagnostics, or OBD-II, to read a vehicle’s computer history and determine if its emissions controls are functioning properly.

According to Drive Clean officials, the new test is 20% more effective at identifying emission problems because it reads the emission information stored in each car’s built-in computer.

Previously, testing required running on a rolling chassis dyno, requiring shops to read tailpipe emissions under simulated driving conditions.

“The testing is a lot quicker and you have to take pictures of the car, plus the Ministry can do an online audit with you live via the new system’s webcam,” explains Chris Owens, owner of Durham Auto Works in Oshawa, Ont.

Although OBD-II testing is new to Ontario, it has been operational in more than 33 provinces and states in North America for some time now. It has proven to be faster and more accurate than the old tailpipe test. It’s also better at identifying any needed repairs.

“They can actually talk to me live, which is much better than calling me up to ask about a car I looked at three or four weeks ago,” adds Owens.

Drive Clean tests are mandatory for the 2.1 million drivers who live in the corridor from Windsor to Ottawa. They are required for vehicles that reach seven model-years old and are sold to non-family members. The price of the test ($35) remains the same.

Cars and trucks are responsible for nearly one-fifth of all Ontario-generated smog-causing pollution. Every year, Drive Clean removes more than one-third of this pollution. This is a real health benefit to us all, and particularly to anyone with respiratory challenges.

“So far so good,” says Raymond Lee of Lee Automotive, in Thornhill, Ont. “The testing does go much faster with the new system. Before, there was a lot of setup time involved when using the dyno and tailpipe sensor. Now, if the vehicle is a 1998 or newer, we just hook it up to the new OBD-II scanner, which is connected to a desktop computer that the new unit comes with, and the information is uploaded to the Ministry automatically. If there are any issues with the vehicle, they can contact me via webcam and discuss the issue while the car is still in the shop,” explains Lee.

While the new OBD-II test is faster and more accurate, there will be a bit of a learning curve for those consumers who tend to ignore their check-engine light and show up for their emission test on the last day.

“If the check-engine light is on the vehicle will fail the test, so the problem has to be diagnosed and fixed, then the owner will have to drive their car for two or three days to reset everything before it can be re-tested.

“I can see this being a real problem for people who tend to leave their emission test to the last minute,” says Owens.

Recent Changes to Standards

While the Drive Clean program continues to play an important role in keeping our air clean of smog-causing pollution, emission testing and repair staff could have a huge impact on verbal pollution by giving clients a heads-up on these recent changes.

It’s safe to say that everyone wants to reduce the amount of pollution produced by motor vehicles. In order to encourage this, governments have introduced tougher and tougher exhaust gas emission legislation.

The most popular method used by vehicle manufacturers is the three-way catalyst. This device converts the main pollutants in the exhaust gas to less harmful gases. However, the three-way catalyst only works efficiently if the air-fuel ratio can be kept within very tight limits. This is where the oxygen sensor fits into the picture.

The oxygen sensor is typically situated in the exhaust pipe just before the three-way catalyst. The central element of the oxygen sensor is exposed to the exhaust gas.

The oxygen sensor continually detects the oxygen content in the exhaust gas. Its output signal is connected to the ECU and changes to indicate a rich or lean fuel mixture. Through its output signal, the sensor “informs” the ECU if the vehicle is running rich or lean. The ECU uses the information supplied to it by the sensor to decide whether it needs to strengthen or weaken the fuel mixture to achieve optimum air-fuel ratio. This is referred to as “closed-loop control,” because the output (oxygen content in the exhaust gas) is measured and fed back to the controller (ECU), which can then correctly control the fuel mixing system. By ensuring that the mixture strength is always correct, both combustion and catalyst efficiency are optimized.

Visual inspection by itself is not usually sufficient to determine if an oxygen sensor is functioning correctly; however, the lead wire and connector should be checked for damage. Any damage will interfere with the sensor signal. The sensor body should be checked for dents, which are a sign of mechanical shock that can crack the sensor element. Also, the appearance of the sensor’s protection tube can give an indication of possible problems.

“Now most vehicles have four oxygen sensors on a car, versus the one or two we’d see a few years ago,” explains Owens.

“OEMs now do pre- and post-converter, left, and right sensors. And these oxygen sensors can cause a lot of problems. They can cause misfires, driveability problems, and there is no code for them, so it takes a bit more diagnosing to find the actual problem,” he adds.

“Many technicians will say, ‘Oh, I have an O2 sensor code,’ so they change the sensor, but they still have the same problem. Just because there is a code for an oxygen sensor doesn’t mean that’s what it is. Something is affecting that sensor and you have to figure out what it is,” says Owens.

Increasingly strict, federally mandated emissions regulations demand that technicians ensure the vehicle’s emissions controls are in optimal form, and the oxygen sensor plays a vital role in this process. In fact, bad/poisoned oxygen sensors are the leading cause of excess harmful exhaust emissions, contributing to the greenhouse effect.

Because of the importance placed on the service life and role of the oxygen sensor on a vehicle’s emissions controls, much has been written by aftermarket manufacturers and suppliers attempting to determine the life expectancy and replacement intervals of oxygen sensors. Real-world conditions, however, truly dictate an oxygen sensor’s life span. Due to the hostile environment in which sensors operate and the very different circumstances and drivers each vehicle experiences, it would be impossible to definitively establish what the service life of a sensor should be.

Oxygen sensors are subjected to a considerable amount of wear and tear, aging, and extreme temperatures even under normal operating conditions. Harmful contaminants that may be present in a vehicle’s exhaust stream can significantly reduce the lifespan of an oxygen sensor. Factors that affect the lifespan of the oxygen sensor include the location of the sensor on the vehicle’s exhaust system. Sensors located directly in the manifold (usually, one- and two-wire sensors) typically have a shorter lifespan, due to the higher temperatures under which they operate and the increased exposure to harmful exhaust particulates (unspent fuel/oil).

Conversely, sensors that have a heater in the thimble element (three- and four-wire sensors) are more quickly brought up to operating temperatures, and therefore are exposed to less harmful contaminants and operate under lower exhaust temperatures, as they can be located further downstream in the exhaust system.

Many automotive manufacturers, like Honda, Toyota, and Nissan, specify when to replace these oxygen sensors, usually somewhere between the 160,000- and 200,000-kilometre mark. This technology doesn’t normally wear out as long as everything is kept up.

“But I find a lot of people don’t maintain their cars and end up ruining a lot of sensors, which costs them a lot of money in the long run,” adds Owens.

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