Had you done the work yourself I would be even more inclined to think "coincidence". You're right about one mechanic defending another one, but not for the reasons you think. It's because of the types of things I mentioned previously. Your average car owner today is very unknowledgeable about the cars they put so much trust in and as a result they feel mechanics will automatically take advantage of them. Add to that some independent shops DO take advantage of people and a few chain outfits are just as bad, and you can see why the industry has such a bad reputation. But it's because of that reputation that some people assume ALL shops are out to get them.
I worked part-time for over 30 years in a very small tv repair shop in a tiny community of less than 2000 people. My boss was extremely ethical and honest and squeaked out a modest living for two people, plus me. I also helped out for a few years at a different shop in my extended community of over 100,000 people. That owner's motto was "I have to rip people off as much as possible the first time because they aren't coming back a second time". (His words; not mine). He was a fantastic technician, and I only stayed there because I learned a lot, but I also learned many ways you can be cheated, so I know better what to watch for. He went out of business many years ago due to lack of customers. We had one other shop that was equally as bad. He too went out of business a long time ago. Now we have only one left in town, and fortunately he is also very ethical. Regardless, only the bad reputations stick and apply to the entire industry. The two shops with the good reputations are well-known within their communities but that reputation doesn't extend to the entire industry.
From listening to conversations at manufacturer's schools, it became apparent that a person could be an expert on one brand of tv but appear to be totally incompetent on a different brand. The brand of tv you brought in for service could determine your opinion of that shop. The crook I mentioned was also a franchise dealer for one of the least reputable tv manufacturers. They are well-known for not paying for warranty repairs and for deceptive business practices that, in my opinion, rip customers off. The company name was so bad, they had to introduce a third brand name about 20 years ago to sell to the people who said "never again" to their first two brand names.
Cars can be the same. I became an alignment and brake expert from working at a mass merchandiser's auto shop in the '80s. I became a Dodge expert later while working for a very nice family-owned Chrysler dealership, but even with all my tv experience, I was not the best at diagnosing automotive computer systems. It wasn't until I started teaching that I learned the little details of charging systems and computer sensors. You may feel free to think I'm an expert, but I'm only an expert on the GM, Ford, and Chrysler products the Auto Shop owned for students to practice on. I spent hundreds of hours over nine years breaking those cars and developing the most efficient diagnostic routines with clues and hints. THAT'S what made me an expert on those few systems.
Mechanics are typically people who learn best when they can touch, manipulate, and inspect something. They don't do well with things they have to visualize, like electronics. Simply understanding that they learn better in a certain way opens the way to tailor their instruction around things they DO understand. For that reason I had very good results with my graduates. It helps too that I'm not particularly bright. Very intelligent people do not make good teachers because they get frustrated when other people don't catch on as quickly as they did.
How did I get on that line of discussion? Getting back to defending mechanics and shops, the biggest problem I've seen is poor communication. Mechanics have no trouble explaining something to another mechanic, just like a doctor to a doctor, but they are very poor at explaining things in an understandable way to customers. That adds to a customer's suspicion and mistrust. Add a service adviser to the mix and you have more trouble. Most of them never were a mechanic. They are supposed to be like an advocate for the customer. A mechanic can tell the adviser what problem they found, and the recommended fix, and if you're lucky, he will understand. Next, he has to interpret that to you, and you can be sure in his attempt to make it understandable, something is going to get lost in translation. I was often asked at school to interpret and explain someone's repair bill, and very often simply explaining what their mechanic did and why was enough to calm people down.
Now, as far as outright defending any repair shop just because I'm a mechanic, that is absolutely not true. We are lucky in my city to have a real lot of reputable shops including all but one new car dealer. We have one independent shop that is well-known among other shops to be not the most ethical all the time but people flock to him because he gives the impression of looking out for his customers. There really isn't a good way to fight that undeserved good reputation without a shop cutting itself down in the process, so people just let him be.
We actually find the opposite of what you would expect to be true, and I don't condone this either. Some shop owners will tell you the OTHER guys down the road can't be trusted or are going to rip you off. Those people TELLING those stories are the ones I don't trust. They think cutting someone down is going to build themselves up, but that rarely happens. Who wants to hear people bad-mouthing someone else. Instead, if a shop wants to gain credibility, they can simply provide a second opinion on a planned repair, then do a better job than the other guys at explaining why their plan is better or more advantageous, even though it might cost more. There are so many variables to some repairs, just like you can find different treatment plans from different doctors. In some cases using a used part is perfectly fine. The other guy might want to install a new part. A used mirror will last just as long as a new one, but save you money. One shop might not have a used mirror, but a different shop might be already having other parts shipped in from a local salvage yard, so just add one more part to the order. It takes just as much work to install a new tire as it does for a used tire. The used one might cost less but it won't last as long. YOU have to decide which is more important at that time.
Some mechanics can or will only replace frayed wires between the door hinges by replacing the entire wiring harness from the dealer, but those are ridiculously expensive. In the tv repair business, we regularly troubleshoot right down to the individual defective component(s) and that's all we replace. Because of that experience, and because I never was one to throw money around needlessly, I prefer to repair the frayed wires. The cost of the replacement pieces of wire is extremely low, but it can take a couple of hours to replace all of them. At $100.00 per hour, do you want it fast with an expensive new harness, or lots of labor dollars with almost no parts cost?
Some mechanics are better at finding worn parts in steering and suspension systems, and some only find those parts that are obviously ready to cause an accident. Some cars have "pattern" failures and we know what we're going to find wrong as soon as we see one pull into the parking lot. '80s Ford Escorts and Tempos were called "killer cars" because of their outer tie rods that fell apart, often in as little as 15,000 miles. Almost every one we saw needed both replaced. But what would you think if your mechanic only found one bad? He might recommend replacing just that one; after all, it's unethical to replace parts that aren't bad. Or, knowing their history, he might recommend replacing the second one right away because it has the same mileage and is going to be worn out soon too, right? What he might not know is someone else could have replaced the second one a month ago. So is he trying to rip you off by selling you an unneeded part, or is he looking out for your safety? He might be looking out for your wallet. An alignment is needed after replacing one tie rod end. If the second one is replaced later, the car must be aligned again. Do both tie rod ends now and you only have to have it aligned once. In the long run that can save you over fifty bucks.
I could go on for hours sharing things like these until my fingerprints are worn off from typing, but I think you get the idea. Some shops have lower labor rates when a less-experienced mechanic works on your car. Tires and oil changes don't require much advanced training. Diagnosing intermittent engine running problems can leave the most experienced mechanics perplexed. They earn their bucks by learning how to diagnose things most other people can't. Some shops perform brake jobs like I would do on my 23-year-old Grand Caravan and just replace the pads or shoes and machine the rotors or drums. That minimal service will usually get you perfectly acceptable braking but on occasion the customer might return with a complaint of unusual noise or feel, then the shop has to fix it on their own time. Other shops replace hardware like anti-rattle springs and return springs that have become weak from being hot so often. Doing that is meant to restore the brake system to exactly like when it was new. Most of the time you and I aren't going to tell the difference which kind of brake service we got except by what's listed on the bill. Here again, communication is important. The service adviser should explain exactly what you're going to get for your money, or he should give you well-explained options.
I have one more comment that I couldn't figure out where to squeeze it in. It's related to the very good shops in my city. From time to time a new shop opens up that does poor work, either intentionally to make more money, or just due to lack of training and / or experience. Those shops don't last very long. We still laugh about the wrecks two used car dealers pawned off on people many years ago until they had so many complaints they couldn't find any more customers. In that regard, the industry tends to police itself. There are a lot of people trying to do right by their customers, so there's no need to resort to unethical practices. Reputable shops have plenty of work to keep them busy. Unethical shops, like those two tv repair shops, have to make a living on fewer and fewer customers. That means they have to get more money from each one some how.
Okay, so what was the question again? Oh, yeah, codes.
P0443 Evaporative Emission Control System Purge Control Valve Circuit Malfunction.
P0748 Pressure Control Solenoid Electrical.
P0622 Generator Field "F" Control Circuit Malfunction.
P1495 Leak Detection Pump Solenoid Circuit.
The only service manual I have for an '01 is for a Durango but the code numbers should be the same. I don't have a listing for codes 32 and 38. Other than two different codes, they only list three-digit codes.
443 and 1495 refer to the pump that pressurizes the fuel vapor recovery system so it can be checked for leaks while you're driving. 748 refers to the governor circuit on the transmission. If the transmission is shifting properly, I suspect they set this code by turning on the ignition switch while something was unplugged. That would make sense too with the other two codes. It's unlikely two different problems developed at the same time except by unplugging a connector or connectors and turning on the ignition switch.
622 refers to the alternator field winding which goes to the voltage regulator in the Engine Computer, (PCM). This is the code that would have most people replacing the alternator first, then looking further when it didn't solve the problem. It's the logical suspect but tests should be done first to rule out other possibilities. There's only two voltages to measure on the two small wires on the back of the alternator. Had they done that, they would have known a new alternator wasn't going to be the solution. The computer monitors current flow through the alternator's low-current input circuit. It turns that current fully on then fully off about 400 times per second. It varies the ratio of on-time to off-time to regulate the average alternator output. It sets this code when it doesn't see that switching taking place. If the charging system is working now, that code will no longer be relevant but it will remain in memory until it is erased. What's puzzling though is why that code exists at all in a new computer. Codes are erased when the battery is disconnected or when the computer is unplugged. That code would have been in the old computer. It would only also be stored in the new computer if something was left disconnected when they put the new computer in and turned on the ignition switch. Perhaps, (just thinking out loud), in their testing after installing the new alternator, they left some other connector unplugged, then installed the new computer before they caught that plug. THAT would put that code in the new computer, but in that case they should have tried the old computer once the plug was reconnected. Had they found out your old computer was okay, that can be a problem area. Parts suppliers rarely are willing to accept return of electrical parts, especially computers, for two reasons. First of all they can't easily prove it wasn't damaged by a wiring problem on the vehicle or through careless handling. Second, if you're paying for a new, (or rebuilt) computer, that's what you want. The dealer or other parts stores don't want to be giving you a used part when they're charging you for a new one. That's the main reason we do a lot of testing to rule out other things rather than ordering a new sensor or computer that can't be returned. A sensor that was ordered through misdiagnosis can sit on the shelf until someone else needs it, but a computer might never get sold. That represents breakfast not on my boss' table tomorrow. All shops already have a lot of money tied up in inventory that is never going to be sold. The better ones are very careful to buy parts they know are needed and are going to be sold.
On the other hand, there are so many things today that can't be tested or that can't be verified except by installing a new computer. If something broken now works, you know it's fixed. If you install a computer to fix something that only acts up once a week, and it works with the new computer, is it fixed or has it just not acted up yet? Boy, mechanics love those problems, (and so do owners)!
The point is, what does the shop do with that new computer if they find it isn't needed? The ethical thing to do in my mind is take it out and not charge you for it, but then what if they can't return it? Most will look at it as an unwanted "investment" that might pay off in the future if they can find someone else who needs it. Some shops will outright lie to you or the mechanic might lie to his service adviser to cover his mistake, and you'll end up paying for an unneeded part. The mechanic might not do that all the time but if he misdiagnoses too many expensive problems, his boss or manager is going to start looking very closely at what it's costing them to employ him. Some people will look at it from the standpoint of reliability. Remember my story about pattern failures? GM used to have a lot of trouble with Engine Computers. Out of 100 replaced computers in the '80s and early '90s that really solved a problem, 98 would be on a GM product and the other two on every other brand. Had someone unnecessarily replaced one of those computers they might rationalize, "it's going to fail anyway, and this way they have a warranty on it".
I have the luxury of owning a spare used computer for my minivan, but I only have the one van to worry about. It was so nice to be able to plug it in the few times I had a running problem because that proved the problem was something else. I'm still running on the original computer after 230,000 miles.
Getting back to those codes, every one of them represents a problem that COULD lead to an increase in emissions. Those codes cause the Check Engine light to turn on. If your light is not on now, that means the codes were set in memory earlier and the problem no longer exists. We often set codes accidentally when we have things taken apart, then turn the ignition switch to unlock the steering wheel or shift to neutral. If we go too far to where power to the computer turns on, it will instantly detect many of those problems and set the codes. That happens all the time, but the final step in any repair procedure is to erase any codes. To not erase them will lead to confusion for the next person who tries to diagnose a problem.
There are three ways to erase codes. The poor man's method is to disconnect the battery for a about half a minute. Because of all the computers and their memory circuits charging up when the battery is reconnected, blown fuses sometimes result from the momentary current surges. That is merely an inconvenience. The computer also stores "long-term fuel trim", (LTFT), and "short-term fuel trim", (STFT) data in memory. Those numbers tell it how much fuel to add or subtract from the amounts pre-programmed at the factory. All of that data is lost when the battery is disconnected, but it will begin to be rebuilt as soon as you drive the truck. Except in very rare instances, you won't even notice anything unusual.
On older vehicles, if the problem does not reappear, a code will erase automatically after starting the engine 50 times. That's about two weeks for most people. I don't think that has changed for an '01 model.
If a mechanic connects the Chrysler DRB3 scanner and reads the codes, it will even tell how many starts since those codes were set, and in some cases how many minutes since they were set. That can help determine if a car came in with a code or if the mechanic forced it to set in the shop. The codes can be quickly erased with that scanner. Most aftermarket scanners can read and erase codes but not all of them will show how long they have been in memory.
The evaporative emissions system collects expanding vapor from inside the gas tank, stores it in the charcoal canister, then it is purged and slowly burned in the engine. There's a system that checks it for leaks, including from a loose gas cap, and it monitors the valves that control that purged vapor. Leaks result in vapor going into the atmosphere. A problem with the valves can allow pressure to build up until it vents through a valve in the gas cap. Either of those result in emissions, so the Check Engine light is turned on with those codes.
A charging system problem usually results in low system voltage. Computers get confused and don't work properly, and the spark could be weak resulting in misfires. That and injectors firing weakly will increase tail pipe emissions, so that code will also turn on the Check Engine light.
I think the transmission solenoid code will turn the light on too. The thinking is if it shifts at the wrong time or doesn't go into overdrive, more fuel will be used even though the level of emissions might not go up.
So, ... If the light is off, none of those codes are currently occurring, and the codes should erase on their own. If the light IS on, the problems that set those codes could still be gone. Codes have a level of severity. Minor ones don't turn the Check Engine light on. Emissions-related codes turn the light on but if it's minor, the light will go off as soon as the problem goes away. More serious codes cause the light to "latch" on even if the problem goes away. It will turn off when the engine is stopped and restarted but the code will still be in memory. If it was a more severe problem, the light will turn on anytime the ignition is on even if the problem hasn't reoccurred. If the light is flashing, BAIL OUT! That means stop the engine. Too much raw fuel is going into the engine and the catalytic converter(s) will overheat and be damaged.
To boil that all down, if the light is still on, the first thing to do is have the codes erased, then see if any of them come back. If they do, look for a disconnected electrical connector as the most likely oversight, especially given the recent track record and the type of service performed. One nice thing about Chrysler Engine Computers is when the light turned on, there WILL be a code to be read. On some cars, GMs in particular, there can be "pending" codes that cause the light to turn on when no code is set yet in memory. That can be frustrating for mechanics and owners. All Engine Computers have a set of rules they follow to determine when to set a code. Part of that is to watch some problems it has noticed to see how many times it acts up in a given time period or series of self-tests. On most cars the light is not turned on while the computer is still evaluating a problem that is not severe or constant. Misfire detection is one example. GMs like to turn on the light while a situation is still being watched. Some scanners will display those pending codes but you have to know how to find them. Otherwise you're left scratching your head.
Well, as Paul Harvey used to say, I told you more than I know. Use what information you can. I'll be here if you have more questions or comments. We can continue this conversation too over private e-mail if you want to since this isn't going to help other people researching a possible fix for their car or truck. If I don't know the answer, I'll make something up!
Monday, December 5th, 2011 AT 5:31 AM