Troubleshooting exhaust emissions

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TROUBLESHOOTING EXHAUST EMISSIONS EMISSIONS ALL PHOTOS COURTESY OF SOUTHEAST MOBILE TECH

The best tools i n your arsenal are your sense of smell, your sight and your ears W By Edwin Hazzard When a vehicle comes into your service bay with a drivability problem you immediately start to wonder if this is could an ignition problem, a fuel problem or some kind of electrical issue that’s happening that would make this vehicle act up enough for the customer to bring it into your shop. As vehicle technology has changed drastically over the years, there are still some things you have to remember that haven’t changed. Even though the internal combustion engine platform has evolved over the years, the same basic principles have stayed the same. e same old adage is true. Every four stroke engine is the same. ey perform intake, compression, power and exhaust. No matter what the problem could be with an engine that has a drivability-related issue, the mechanical integrity has to be working absolutely correct. is is especially important on today’s engines that have a control module keeping an ever watchful eye on any problems that could crop up. When I go into a shop to perform a diagnostic repair I try to give the technicians who are with me an impromptu training class. One of the things that I like to drive home is the fact that if it’s a drivability problem we will know that no matter what the culprit is that is causing the issue, it can be said that there are only four possibilities that we have to look at. It can be a mechanical problem, an electrical problem, a fuel 38

Figure 1: A turbo charger on a 2019 Chevrolet Traverse.

problem or an ignition problem. at’s it. ose are your only choices. e fun starts when it could be more than one of those four scenarios at the same time! Determining the issue is what makes a service technician a drivability technician. Figuring out how to put together a diagnostic game plan and applying that to pinpoint the problem is what separates a good technician from an elite technician. In this article I will show you an easy way to help you tackle some of these tough drivability problems that can arrive in your service bay.

Emission issues One of the issues that can crop up on a tough diagnostic job is nding out that the cause can be from an emissions-related problem. As you are aware, vehicle design evolution has incorporated multiple emission monitoring and control devices to control the air pollution problems that we have faced over the last three or four decades.

Unfortunately, while they are good for our at-

Figure 2: The arrow indicates the oxygen sensor on a 2001 Izusu NPR.

mosphere they can play havoc on how our vehicles operate at times. These emission-related systems can affect the fuel systems, exhaust systems and mechanical systems of the vehicle.

Diagnosing exhaust emission system problems can sometimes be challenging. The exhaust system’s job is to carry the byproducts of a combustion event safely and efficiently out of the tail pipe. The exhaust piping has a few jobs it must handle besides deliver exhaust gases away from the vehicle. The exhaust system houses some vital components that control emission system operations. Components such as oxygen sensors, NOX sensors (for diesels), exhaust brakes that aid in warm up on medium- and heavy-duty vehicles as well as turbo chargers (see Figure 1) that help aid in the performance of engine emissions. These components not only have to work correctly, but the components have to be securely attached to the exhaust tub-

Figure 5: This shows a cracked exhaust manifold.

ing without any leaks, structural damage and proper placement.

Let’s focus on the gasoline exhaust emission type issues and we will save talking about diesel emissions for another time.

On a modern gasoline engine we can have as many as six, possibly more, sensors that are mounted in the exhaust piping. is can include air fuel ratio sensors, oxygen sensors or catalyst e ciency sensors. On these systems, a turbocharger could be added along with a couple of catalytic convertors.

An example of a failed emission scenario would be an oxygen sensor that is mounted in the exhaust pipe and there is a crack in the mounting area that is not only causing a leak in the system but the sensor is picking up extra air that shouldn’t be there (see Figure 2). When that happens it will make the fuel trims start to rise and start demanding more fuel to be added as the ECM is seeing the extra air as a lean running condition.

You can see in the screen shots that bank 2 is going lean at idle as there is more air in the system due to a small leak by the exhaust sensor mounting area (see Figures 3 and 4).

Other areas of the exhaust system that can cause a drivability issue include a cracked exhaust manifold (see Figure 5), manifold gaskets that don’t seal at the cylinder head due to a loose manifold mounting issue or even broken manifold mounting bolts.

When diagnosing exhaust-related drivability issues, the rst step is to do a complete visual inspection along with looking at scan data and watching fuel trim movement. Using a CO2 tester such as the ATS Bullseye leak detector (to cite one example — see Figure 6) will work to nd an exhaust leak in short order. Other methods of checking an exhaust system for leaks include the use of a thermal imaging camera (see Figure 7). Looking for the “hot spots” will reveal a potential leak point. 40

Figure 6: The ATS CO2 detector, as an example.

e electronics in today’s vehicles are programmed to the tightest tolerances when it comes to monitoring the emission systems due to the fact that the vehicle manufacturers have to meet a certain criteria that is mandated by the federal government. Any deviations or compromises in the exhaust will skew the emission monitoring process and alert the vehicle’s on-board diagnostic system that there is a problem. So what does this all mean?

Let’s take a look at a common scenario. A 2005 Ford F-150 with a 5.4L rolls into the service bay with the check engine light illuminated. I scanned the truck for codes and nd a P0174 stored. is code is for a lean condition on Bank 2.

I started the engine and immediately noticed that the truck sounded a little louder than normal. e one thing that I stress when I’m conducting training classes is that the best tools you have in your arsenal are your sense of smell, your sight and your ears. No matter how focused you are on the repair, always pay attention to your surroundings. Because I was able to hear the unwanted noise in this truck I immediately focused

Figure 8: A screen shot using the ATS Escan showing a lean condition.

Figure 7: Here’s an example of a thermal imaging camera.

my testing procedures based on my sense of hearing the noise rather than to start testing for the most common issue involving the fuel system and/or vacuum leak tests.

To verify that the engine is running lean I connected my scan tool and took a look at the oxygen sensors. I wanted to see if they were switching and moving correctly.

In Figure 8 you can see that the sensors are switching but the oxygen sensor on Bank 2 isn’t moving while the sensor on Bank 1 is moving. Notice the lack of movement or hesitation you see in the voltage travel? This is verification that Bank 2 is showing a lean condition just as our code indicates.

Notice to the left of our oxygen sensor screen shot that it shows a fuel control problem along with a fuel trim issue being in orange instead of green like Bank 1. Here is another screen shot (Figure 9) showing this verification. So what’s our next step? We know what code is set.

We have verified that Bank 2 is running lean compared to Bank 1. Let’s do a visual inspection and see where our noise is coming from and if in fact that is what’s giving us our lean running issue.

We see in Figure 10 that there is a broken mounting bolt that attaches the exhaust manifold to the cylinder head. With the mounting bolt not 42

Figure 9: A screen shot using the ATS Escan showing a fuel control problem.

holding the manifold tight to the cylinder head as the engine is running it is picking up unwanted outside air entering the exhaust system and the oxygen sensor is picking up that unwanted air and reporting it to the vehicle’s engine computer.

As the engine reaches operating temperature the exhaust manifold expands and creates a bigger air gap to allow more air into the exhaust stream.

When diagnosing a problem like this you have to put together a game plan. You have to have an understanding on how the system operates. Doing that will go a long way in nailing down the problem at hand.

Other exhaust-related drivability problems that can arise would possibly involve catalytic convertor problems that could set codes like a P0420, P0430 or even rich or lean codes depending on the condition of the catalytic convertor. A catalytic convertor is usually tested for efficiency by the vehicle’s engine computer. A convertor can have issues that can make it fail due to a rich running condition such as a fuel injector dumping too much fuel or a cylinder misfire that is pumping unburned fuel through the exhaust system and contaminating the insides of the convertor assembly.

Figure 10: Example of a broken exhaust manifold stud on a 2005 Ford F-150.

When that happens it can deteriorate the efficiency of the convertor which could set codes P0420 and P0430.

Looking at the screen shot of a catalytic efficiency test (see Figure 11) on a 2002 Nissan you can see the percentage of the deterioration of the cat — but look closely at the rear oxygen sensor on Bank 2. Notice that the movement mimics the front sensor as the rear oxygen sensor on Bank 1 looks completely different.

Does this mean than the catalytic convertor is bad on Bank 2? Not necessarily. Could there be something that is causing the rear oxygen sensor to read like that? Or could the convertor just be deteriorated internally and the reading of the rear oxygen sensor is correct and doing its job?

This is where a good diagnostic game plan comes in. If you are familiar with working on these vehicles you probably are aware of the many technical service bulletins that are out there con-

Figure 11: An example of a bad rear oxygen sensor reporting a bad catalytic convertor.

cerning these catalytic convertor issues. They range from replacement to ECM recalibrations — or maybe both. It’s always a good idea to do a bulletin search on any vehicle before you tackle a tough diagnostic problem.

Exhaust system diagnostics are not really that complicated. What you have to remember is that the computer systems that are in place on these modern vehicles are always looking at emissions.

Now more than ever these vehicles have to run to the best of their ability. There isn’t much room for error. States that have emission inspection laws know more than anything how critical this is.

My opinion is that all 50 states should have emission laws. Keeping the environment clean and safe just makes good sense.

So with the right knowledge, tools and the proper training, exhaust emission repairs should be second nature. Paying attention to detail when a vehicle is brought into your service bay will not only bring you increased profits but you will be doing your part in repairing these vehicles so the environment and atmosphere is kept clean. ■

Edwin Hazzard owns South East Mobile Tech in Charleston, S.C., which is a mobile diagnostic and programming service providing technical service to many automotive and body repair shops. He has 37 years’ experience in the automotive industry. He currently is an automotive trainer, a board member of TST (Technician Service Training), a member of the MDG (Mobile Diagnostic Group), a member of the Professional Tool and Equipment advisory board for Pten magazine, a committee member of Nastaf, and is a beta tester for multiple tool makers.

TOYOTA STOP/START BATTERY CAUTION

Some 2017-2019 Toyota Highlander vehicles are equipped with an engine Stop & Start system. If the battery is to be replaced, it is important to use P/N 28800-31550. There is no recommended Truestart battery that is applicable for Stop & Start Highlanders. The Stop & Start-equipped battery is specially designed for dep discharges and it is of a design called enhanced flooded battery (EFB). Characteristics of EFB-type batteries are the ability to quickly discharge and recharge.

When testing batteries for Stop & Start-equipped Highlanders, use the battery type “enhanced flooded” (EFB) when using the battery tester. If you are not sure if the Highlander is equipped with Stop & Start functionality, there are several ways to identify them. Stop & Start-equipped vehicles have a Stop & Start indicator light and a button on the dash to turn the system off temporarily. Stop & Start is standard equipment on V6 Highlander LE Stop & Start-equipped Highlanders will feature an indicator light and a push button on the Plus, XLE, SE and Limited models. dash for temporarily disabling the system.

You can also identify the correct battery by looking at the battery label, which should have the part number 28800-31550. The battery manufacturer “GS Yuasa” can be seen on the front of the battery in raised letters and on the battery label. It also has screw type vent caps, not press-in vent caps.

ALL TSB INFORMATION IS COURTESY OF MITCHELL 1

GENERAL MOTORS ROLL AWAY This bulletin applies to a number of GM vehicles, including 2013-2017 Buick Verano models. A recall was announced due to the possibility of the electronic park lock lever potentially allowing the ignition key to be removed without the transmission being placed in Park. In addition, some vehicles may have been serviced with similar defective replacement electronic park lock levers.

If the key is removed without the transmission in Park, the vehicle may roll away as occupants are exiting. Other vehicles involved include Chevy Equinox, Buick Regal, Chevy Cruze, GC Terrain, Buick Encore and Chevy Malibu.s

DODGE WATER PUMP WOES This bulletin applies to 2013-2017 Ram 2500, 3500, 4500 and 5500 vehicles built from October 2012 to February 2017 and equipped with a 6.7L diesel engine that features a Concentric-brand water pump.

A recall was issued because these pumps may not feature a vent hole and may leak coolant.

CHEVROLET FILTER FAIL This bulletin applies to 2017- 2019 Chevy Colorado and GMC Canyon trucks equipped with a 3.6L engine. Some customers may comment on engine noise or engine failure shortly after an engine oil change and a MIL on. The condition may be caused by a missing oil filter adapter insert/bypass valve that was inadvertently removed during The photo on the left shows the center bypass valve in place. The photo on the right shows the valve missing. Whenever performing an oil change, make sure that the bypass valve is in place. a previous oil change. Also, the retaining tabs on the insert may not be robust enough oil galleries causing an upper engine noise. If no to retain the insert during an oil service if the filter mechanical damage is found, inspect the oil filter is crushed. for damage. If there is paper debris, codes and/or

If a vehicles comes into your shop with one cam actuator noises, that does not require engine of these conditions, inspect the oil filter adapter replacement, repair and/or replace the affected to see if the center insert/bypass valve is miss- components and clean the engine thoroughly. ing. Upon inspection, the technician may find If engine noise is present, it will be necessary to that the oil filter has been damaged or material inspect the engine to see if any damage has ocfrom the oil filter may have been pushed into the curred such as a damaged rod bearing.

MERCEDES-BENZ BENZ OVERFILL On Mercedes-Benz gasoline engines, equipped with an oil level/oil pressure sensor, the instrument cluster indicates that the engine contains too much oil. The cause is likely that the vehicle is mainly driven in the city or used for short, frequent trips where engine operating temperature might not be reached.

With frequent cold starts and lots of short trips, fuel can enter the engine oil in non-combusted form. Fuel outgassing through crankcase ventilation is only possible once the operating temperature is reached.

If operating temperature is not reached, the ingressed fuel collects in the engine oil which in turn leads to a significant increase in the oil level. The reduced viscosity can cause engine timing malfunctions and the engine oil’s lubricating characteristics are reduced.

On vehicles that are primarily used for short trips, the engine oil level should be checked on a regular basis. Replace the engine oil and filter.

TOYOTA DON’T FORGET THE BREATHER Toyota strongly recommends replacing the breather plug whenever servicing any differential/transfer case to prevent possible repeat failures. The use of the original breather plug after a repair has been found to contribute to the failure of the differential/transfer case components.

Applicable vehicles include 4Runner, FJ Cruiser, Land Cruiser, RAV4, Tacoma and Tundra.

PORSCHE INTERMITTENT PORSCHE CONTROL This bulletin applies to 20142017 Porsche Cayenne S and GTS vehicles. You may experience a symptom wherein the engine will not start at times and the fault code P0607 (control unit faulty) is stored in the fault memory.

The DME control unit can become damaged via the electrical wires as a result of electrostatic discharge of the throttle housing. The optimized throttle housing with insulation has been installed during production since Aug. 24, 2016. For vehicles built before Aug. 24, 2016, the DME control unit and throttle housing must be replaced in the event of a complaint.

LINCOLN PARKING SENSOR ISSUE This bulletin applies to 2017-2019 Lincoln Continental, 2019 Nautilus, 2015-2019 MKC, MKT and MKZ, 2015-2018 MKX and 20152019 Navigator models. Some vehicles may experience front or rear park aid sensor false alerts with no diagnostic trouble codes present.

False park aid alerts with no DTCs in the park aid system are usually due to snow, slush, fog, salt, ice, frost buildup, car wash or heavy rain. Each sensor features a silicone ring designed to absorb vibration and to reduce false alerts. A thin film of ice, etc., may bridge over the silicon ring and/or sensor, causing a false alert.

Upon visual inspection, there may be no obvious obstruction with the sensor. Often, when the vehicle is brought into the service bay, the ice will melt and all evidence of frost/ice will no longer be present. Diagnostics should be performed but if no DTCs are present, then the ice bridging on the sensor was likely the issue.

Verify that sensor alignment and ring place-

Example of a parking aid sensor. 1) Sensor; 2) Park aid sensor silicon ring; 3) Park aid sensor retainer.

ment is symmetrical. If no issues are found, advise the customer that this is a normal vehicle characteristic. Advise the customer that they have the ability (on some vehicles) to turn the park aid system off in certain weather conditions.

FORD AMBULANCE BRAKE LIGHT ISSUE Taylor Made Ambulances is recalling certain 2017-2018 Ford E-350, F-450, E-450 and F-550 ambulances equipped with Whelen brake lights. Depending on the specific wiring of the vehicle, the brake lights may illuminate when the brake pedal has not been depressed.

CHRYSLER BAD WELD Chrysler issued a recall for certain 2018 Jeep Compass vehicles built in January 2018. The front lower control arms may be incorrectly welded, potentially resulting in a control arm separation.

MAZDA SLOW MAZDA? • Select Modules • Select PCM • Select the following PID from the PID table: Owners of 2016-2018 Mazda CX-9 vehicles – FP_DUTY (fuel pump control module conproduced before Nov. 10, 2017, may experience trol duty value) a lack of power with no warning lights illuminated • FUEL_LO_T (fuel temperature inside the and no related DTCs stored. This concern most fuel supply line) likely occurs when fuel temperature is high and • Mark a point on the graph for the PID data during situations where high power is required. and verify if the point is located above the line (in

This concern may be caused when the learn- the poor performance area) or below the line (in ing value for the low pressure fuel pump exceeds the normal performance area). a certain level and the PCM limits engine power For example, if FP_DUTY is 55% and FUEL_ to avoid a lack of fuel injection. Even if the low LO_T is 40 C, the point is located in the poor perpressure fuel pump has a problem, no DTCs are formance areas. stored. • Reboot the IDS to clear memory before re-

To eliminate the concern, the PCM control programming. logic has been modified not to limit engine power. After this modification, DTCs P0192:00 or P0087:00 are stored when the fuel injection amount is insufficient.

P0192:00......high fuel pressure sensor circuit low input

P0087:00.....high fuel pressure sensor circuit range/performance problem

Inspect the low pressure fuel pump using the Mazda Modular Diagnostic system (M-MDS). If the low pressure fuel pump exhibits normal performance, reprogram the PCM without replacing the fuel pump. If the low In the example shown here, 1) Poor performance pressure fuel pump exhibits poor per- area. 2) Normal performance area. formance, replace it after reprogramming the PCM. • Using IDS 108.03 or later software, repro• Connect the M-MDS to the DLC-2. gram the PCM to the latest calibration. • Warm up the engine and leave it at idle with • After performing the PCM reprogramming the least amount of electrical loads on. procedure, clear all DTCs. • After the vehicle is identified, select the fol- • After clearing DTCs, start the engine and lowing items from the initialization screen of the confirm that no warning lights are on. M-MDS: If the PID data is in the poor performance • Select Datalogger area, replace the low pressure fuel pump.