Auto Repair Diagnosis
Let’s go through a few car repair diagnostic processes to see whatâs really involved in diagnosing a number of problems.
Now clients often are concerned about the cost of diagnosis. They donât understand whatâs involved.
âDonât you just plug a computer in and tell whatâs wrong?â If only it were that simple!
Diagnosis for Check Engine Lamp – Acura 3.2 TL
Customer complaint was that the check engine light is always on yet the vehicle runs fine.
Once we plug the computer inâ¦ that only gives us some clues as to the problem. To find out whatâs wrong we have to follow up with further tests.
We can scan the vehicleâs computer and get the basic information about what codes are stored in the computer.
The scan tool shows there are several codes that are stored. First, the P1676 Iâm not certain of so weâll have to look that code up. Thereâs a number of engine misfire codes from cylinders 1, 4, 5, 6 and thereâs also a code for the Evaporator system.
Next, we take the vehicle on a road test. Driving for a little while reveals the engine doesnât appear to be misfiring. It seems to be OK.
Back at the shop, letâs break down those trouble codes that were shown on the scan tool referring to 3 different systems of the vehicle. The first issue P1676, is a communication issue between the transmission computer and the vehicle computer.
The second issue is the many engine misfire codes. The third issue is the P1456 Evap code and that seems to be involved with the fuel cap. That has been a very common failure on this vehicle.
These are the first steps in diagnosing a modern vehicle that has the check engine lamp on. The test procedures vary based on the vehicle, the type of concern, and the codes provided.
It is not simply a matter of plugging in the diagnostic computer and having it tell us exactly what is wrong. The computer is only part of the diagnostic process, giving us trouble codes and feedback information that the vehicle computer stores.
From here, we must test specific components and wiring circuits to find the real cause of the concern.
How to get Commercial Auto Repair
Vehicle History Overview
- They don't make them like they used to.
The First Cars
- The first motor cars were nothing more than a buggy and engine (Generally repaired by blacksmiths and carpenters. These cars were very expensive, which only the wealthy could afford)
- Model T was the first car mass production on an assembly line in 1908 (Ford's Vision was to produce an affordable car the average person could purchase)
- Model T's came in black only to keep the costs down. (The price came down once the assembly line was streamlined, but in 1908, the cost for a Model T started at $825. By 1913 the cost of the car reduced to $550)
Cars in the 1960s
Cars were made the same basic way up through the 60s
- Body Over Frame
- Rear Wheel Drive (Same concept, but the cars were very big, bulky, and heavy)
Except people in the 60s wanted SPEED! They achieved this with Big Block Motors, which created a lot of Horsepower. (The Birth of Hotrods, Rat Fink, Flames, and Pin Striping).
Cars in the 1970s
- The government place strict fuel economy and emissions control laws
- Customers demanded cars with increased fuel economy
- New laws and customer demands started the automotive explosion of engineering ideas and changes in the automotive industry
Changes to comply with Demands and Laws
- Smaller bodied cars and smaller engines
- Aerodynamics (Increase Fuel Mileage)
- Lighter cars by using different materials and designs
- More work-hardened areas created during formation of panel (Body Lines)
Construction of Interstate Highways + Higher Speed Limits + More High Performance Cars = Accidents and More
Deaths from Auto Accidents
Federal Laws were passed to regulate safety. These laws included:
- Installation of seatbelts
- Safety glass windshields
- Head restraints
- In 1979, the first driver side airbag was introduced
- Airbags are mandatory in motor cars produced after 1990
- Unibody Torque Boxes: Allow controlled twisting and crushing
- Crush Zones: Made to collapse during collision (To act as an absorber, absorbing the impact)
Modern Day Cars
- Carbon Fiber Parts
- Aluminum Parts
- More Plastic Parts
- High Strength Steel
- Boron Steel
- Unibody Construction
- Space Frame Construction
- Hybrid Cars
Now they even have cars that will tell you when you're lost, where to turn, Parallel Park for you.
While the modern day cars appear to be made cheap and unsafe, they are actually designed to crush or collapse, while transferring the energy around the stronger passenger compartment to protect the passengers from injury.
There is considerably more damage to modern day cars during a collision than the older vehicles, which gives the perception that "they don't make them like they used to". However, in reality the cars are taking the impact instead of the passengers.
The lesson was designed to give you a little history, but to also emphasize that just a hammer, dolly and a few wrenches are not going to repair today's cars. We need highly trained collision repair and automotive technicians to repair today's vehicles.
Water Leak Diagnosis Lexus RX300
There was a lot of water in this vehicle; the carpet was completely soaked. In fact we could hear water sloshing around through the carpets. The front and back seats, passenger and driver side were completely soaked with water. A real mess. It didnât smell very good either, the leak had been there for quite some time.
To find the water entry point, one of the simplest things we check in any vehicle that has a sunroof is the sunroof drains. Often they will plug up with debris and that will cause water leaks to come into the vehicle. We tested the sunroof drains and in this particular vehicle, they were OK. Some vehicles also have common leak spots and so weâll and check those particular areas. With this vehicle there was nothing, the sunroof drains were good, and the common leak areas were all fine.
From there… things became really complicated. We sprayed water all around the vehicle from every angle and didnât see obvious leaks. There are many places water can leak into a car so this is the first checking action.
We had to strip the interior out of the vehicle so we removed the front and back seats, removed the console, the carpets, removed everything on the floor. We dried everything out because thatâs critical to figure out where the waterâs coming in. We removed everything, hung the carpet out to drip dry, after wringing it out. We drained the water out and dried the inside out, and then from there we were able to spray the car down again and find the leaks.
We found a few things. We found there was a leak in the floor of the vehicle on the passenger side. Thereâs rubber plugs in the floor and one of the plugs was missing.
That was probably a very minor source of water but nonetheless it was a source especially as water will spray up when you’re driving and then can seep in under the floor. Another leaking spot was the right rear door; the seal around the door at the top leaked, and a lot of water was coming into through that.
We were able to reinstall the seal and it worked properly. The seal had slipped out of position, wasnât obviously noticeable beforehand but once we started spraying water, we could see water coming in.
The third leak was the more complicated one. We could see water leaking in under the dash near where the driverâs left foot would be… called the dead pedal. Itâs a spot where you can rest or brace your foot. There was a leak from there as well as a bolt missing so that was allowing water spray in. However, there was another leak further up in the front as well and we couldnât quite see the source of it.
It was coming from somewhere in the front of the vehicle and to find exactly where required a lot of disassembly. There’s much wiring and other equipment located in that area of the firewall. With the fender in place and the wiper linkage and the panels in there, it wasnât obvious where the water was coming from. It could have been ten different places at the back of the firewall. We removed the front fender off the vehicle, the wiper linkage and everything else in the way to finally spray water and found there was a leak at the very bottom left corner of the windshield.
We sent it to a windshield shop and had it resealed.
Then before putting everything back together, we resprayed the vehicle to verify that there was no water leaking. It was fine.
We also had the carpet shampooed as it was in bad stinky condition and dirty so itâs a good thing to do while itâs out.
This type of job is an hour by hour charge, as we have no idea of knowing when we start out where the leaks come from or what itâs going to entail. We can give a rough estimate, of how many hours we think itâs going to take but really it can be anywhere from a couple hours to 10 or 12 depending upon what we have to remove to find the problems and then what needs to be fixed.
In the past; we had a Mazda once where it was a cracked body seam on the passenger side front and the water would just spray in, in certain conditions. We had to pull everything apart inside the car to find it.
When you get this much water in your vehicle you really want to take it apart and dry it out. You can get mold in the car and it’s best to avoid the health issues with that.
2005 Mercedes Benz E320 Electrical Diagnosis
The vehicle was brought to us because the owner was concerned about some rodent chewed wires under the hood. He was also concerned that his battery would go dead over night and there was a couple of dash lights and other lights like the gear shifter light that remained on.
Where we started first was a visual inspection under the hood. Fortunately it turned out that it was really minor. They just nibbled a little bit on the outside of the insulation of a couple wires. We taped it up and it was fixed and done and was no cause for any of the other concerns in the vehicle.
The next step was to hook our diagnostic scan tool up and do a full vehicle system scan. You can scan all the modules of this vehicle.
Many modern cars enable us to scan the whole car, we do that a lot in diagnosis. We look and see which modules have trouble code.
We found a few codes that were related to body control and the CanBus System so thatâs where we started with our issue, but also verified that there was a four amp power draw from the battery when the key was shut off. Thatâs huge, thatâll kill a battery pretty quick and was a big part of why the battery was dead overnight.
CANbus – stands for Controlled Area Network and itâs a communications system used in vehicles to communicate between various modules. On this Mercedes there are at least ten to fifteen different modules, for body control, for lights, for the power door locks, the suspension system, the anti lock brakes, etc. All these modules communicate with each other thru the Canbus. It saves on an awful lot of wiring and allows a lot of complexity and intelligence in the vehicle. Can is used in a variety of different vehicles. Mercedes were early adopters, like they are for many types of technologies.
The problem with this car was there were some communication errors. We started our diagnosis looking into the CANbus system. The way the diagnostic procedure works with this is we disconnect different modules to see which one might be causing the system error. Any particular module might cause the other ones to miscommunicate. Itâs a matter of disconnecting each module and checking for where the error lies… why these lights were staying on and where the excessive battery drain was.
We disconnected everything and were puzzled because the power drain was still there and the lights were still remaining on! We had ruled out any actual problem with the CANbus even though the codes were all from that area.
At this point, we were reduced to disconnecting various components in the vehicle, unrelated items, to find the problem.
What we found was really interesting, something completely unrelated, nothing to give us any clue, but the radiator fan was actually causing the whole issue. The radiator fan is an electric fan with four wires; a power and a ground and a couple for communication, signal wires to turn the fan on and off. The fan wasnât running, it wasnât buzzing, it wasnât doing anything but yet, once we unhooked that all the problems went away which is really, really bizarre.
We looked at the fan and it looked quite new, like this part has been replaced. We call the owner he said âA few months ago the radiator fan motor was dead so I replaced it myselfâ. He did a great job by the way, installed it nicely, and heâs like âcome to think of if, thatâs kind of when all the issues started happeningâ. Turns out he fan motor was defective!
We installed a new fan motor… all the lights were off, battery drain reduced down to about 30 milliamps. Perfectly normal and the car worked great.
The owner installed fan was seemingly working fine. As far as our diagnostic we never looked at the fan because normally if thereâs a fan malfunction on a Mercedes, it sends a trouble code for a malfunction. It did not so the fan I believe was probably working fine if you warmed the engine up. We never got to that point because we were chasing a power draw. More obviously if the fan was actually running while the key was off, well ok thereâs a problem there. Some kind of an electrical fault inside the control units in the fan. Again these things have like little inside, some little malfunction.
As automotive technicians, we follow a diagnostic procedure based on the best information we have. We have to start somewhere.
There were codes for the CANbus and various systems so we followed that and it turned out to be a rabbit hole. What would of been really useful is for the owner to have said, âYou know, one thing that I did do was I did change the radiator fan and the problems seemed to happen from then”.
People tend to forget that almost everything is relevant! Itâs good to think back to anything that may have happened recently; when does the issue occur, is it hot, cold, after running for 10 minutes, those kinds of bits of information are really really helpful for us to diagnose the vehicle.
During these diagnoses you got to see both a simple and a complex diagnosis and we hope that this helps you understand whatâs involved in properly diagnosing and repairing a modern vehicle.
Getting Needed Auto Repair Fixes
If you see fewer auto repair shops in your area then you are witnessing a trend that is spreading throughout the auto repair industry. The small independent auto repair shop is getting squeezed by both the dealers and the 'backyarders' creating shrinking margins and putting many auto repair independents out of business.
The global problem is the auto repair and service market has been shrinking in the last ten or fifteen years. Technology has made cars much more reliable with fewer breakdowns, repairs and scheduled maintenances.
Many manufacturers offer some sort of 100,000 mile warranty meaning that the independent will get little chance to work on that car for the first 5-10 years it is owned.
As new car sales margins have gone down, VW, Chevrolet, Toyota and other manufacturers are looking to their service departments to make up the difference.
Additionally many dealers such as Porsche and Saab have been adding other value added benefits such as a loaner car while repairs are being made. Independents are now being forced to give courtesy rides to customers in an effort to keep up with the dealers since customers now expect this service.
Furthermore dealers such as Mercedes and Ford are now directly offering specials on services making their dealer prices comparable to independent repair shop prices.
But it's not just competitive pricing that is worrying the independents.
The battle for skilled labor is also being won by the dealers: the dealers have always competed for skilled labor and now have become even more aggressive. With fewer young people entering the auto repair profession and opting instead for careers such as health and technology, the total talent pool of the top skilled auto technicians is shrinking.
Increasingly it is becoming harder for independents to hire and retain these highly skilled employees. As an automotive technician, would you rather work for Audi or Joe's Garage?
The dealers are picking up the best 'mechanics' or as they are known today, 'technicians.' A top end dealer technician can make $100,000 a year with benefits while an independent shop owner would have to gross over a $1,000,000 a year to make that and still have to pay for their own benefits and social security.
Because of these economic realities many independent owners are now closing their shops and going to work for GM, Nissan and other dealers.
This puts the independent auto repair shop at a distinct disadvantage when diagnosing and repairing difficult drivability, fuel injection, electronic and computer related problems.
Additionally, if a diagnosis is made and a part needs replacing the dealer will have it in stock, not only verifying the diagnosis but greatly speeding up the repair time and increasing customer satisfaction. Big advantage Cadillac and Mercedes.
But it's not just a skilled employee war. Techs cannot fix cars without information and there has been a long and ongoing dispute between the dealers/manufacturers and independents over technical information access and diagnostic tools.
The manufacturers claim that their technical information is proprietary while the independents claim the information should be available to anyone that owns or fixes that make of car.
If the dealers wanted to they could stop all outside repairs on their vehicles but the problem is there are not enough dealerships to service all geographic areas, especially smaller towns and less populated areas. So the manufacturer/dealer gives out some information but not all, often charging the independent repair shops for this information.
Not only does the independent have to buy some parts from the dealer, but also some of the technical information as well. Big advantage Honda and Dodge.
Some independent owners simply watch their business steadily decline over the years as they go out of business. Younger independent owners are willing to work harder and for less financial reward hoping industry conditions will eventually improve.
In essence the independent auto repair industry has matured and is now in a decline. Some consolidation is going on but much of the repair work has either disappeared or is now being done by the dealers, auto repair chains or one person 'backyard' shops.
The opportunities are there for those that want to work hard but those opportunities are increasingly limited. In a declining market, only those independents that can develop new competitive strategies will survive and thrive.
As with all mature and declining markets there will be new opportunities for those owners that can adapt and make the changes. Those independent auto repair shop owners that don't modernize, strategize and compete will go the way of the Edsel and Model T.
2008 BMW 128i Ignition Coil Diagnosis
When this vehicle came to our shop, it was running rough and the check engine light was on.
We connected the scan tool and found there were several codes stored for engine misfire. What our further diagnosis found was two ignition coils were not operating. There are six ignition coils in this engine – one for each cylinder – and if one or two die, usually the others are not too far behind. Typically when they fail like this, we replace all six. Thatâs what our experience has found with these cars. In the past, weâve done one or two and then the customer often was back in a couple months with another dead coil. It just makes sense to change them all at once which saves money and time, in the long run.
Ignition coil failures are common on these cars. We do quite a number of them and this is a pretty common issue. We see this often with Audis and Volkswagens as well; a lot of German cars, the coils fail. Fortunately they are not overly expensive parts, so to change six of them, or four or eight depending on how many your engine has is not hugely expensive. It is pretty common on these BMWâs.
We also changed the spark plugs. This vehicle had enough kilometres on it that the spark plugs were reaching their end of life age where they need to be replaced. Itâs not a lot of extra work once the ignition coils are out to change the spark plugs. So that makes a lot of sense.
We also changed another part as well. We noted there was an oil leak, a small oil leak from a part called a Valvetronic Motor Gasket. So we replaced that as well.
The Valvetronic motor was right in the same area of the engine. Not a lot of extra work when weâre doing the ignition coils. There was a sort of oily film, thatâs where the leak was coming from.
A Valvetronic motor is an actuator for the variable valve timing. BMW uses an extra arm on the camshaft and it adjusts the valve timing. Itâs BMWâs method of variable valve timing and it works really well. Itâs amazing, the power you get out of a modern engine and this is a device that gives you smooth power from low end to high end today. So the motor basically in a very short amount of time will adjust the valve timing to whatever the computer desires it to be based on load, speed, fuel economy needs, exhaust emissions, itâs all taken into account. The vehicle computer and sets everything, itâs pretty amazing.
Itâs another thing to go wrong but generally the system is quite reliable. Weâve rarely replaced any parts or pieces for it, but given enough time, like anything, itâll break down. This gasket is not an uncommon leak. So just fix them and itâs done.
These ars are OK for reliability… ignition coils, we certainly see a number of those and there is the odd oil leak. I think generally, I think the car is quite reliable.
Thereâs an interesting study that came out a couple of months ago about overall car maintenance costs and the BMW came out as the highest maintenance cost vehicle, so just something to note if youâre buying one.
Interestingly enough, the lowest maintenance cost were Toyota products, Toyota Lexus and Scion.