1996 Chevrolet Silverado check engine light on

P0161 - Oxygen Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)
P0175 - System too Rich (Bank 2)
P0305 - Cylinder 5 Misfire Detected

For the misfire code, start with the basics, spark plugs and wires. If that code comes back after it's erased, switch two injectors between cylinder five and one other one to see if a code is set for the other cylinder.

For code 161, probably the most common cause is a break in the wire going to the rear oxygen sensor. Look also for corrosion in the connector terminals. Don't worry yet about code 175 until the other problems are solved.

Oops. You might have a pair of injectors in the top of the throttle body. Those don't cause much trouble.

Next I guess I'd start with a compression test and a cylinder leakage test. With the mileage you listed, don't overlook a worn camshaft lobe too.

One at a time you put a cylinder on top dead center, then you pump in compressed air into the spark plug hole through the tester. The percent leakage will be shown on the gauge. Typically anything under ten percent leakage is okay, but the real benefit of this test is you can observe where the leakage is taking place. If an exhaust valve is leaking, you'll hear the hiss at the tail pipe. For a leaking intake valve, you'll hear the hiss at the throttle body. Leaking piston rings will be heard at the oil cap or dip stick tube. A leaking cylinder head gasket will show up as tiny bubbles in the radiator.

First try the auto parts stores. Many of them rent or borrow tools. It really doesn't make sense to buy one because you won't use it very much, but if you do want one, ask at any repair shop or dealership when the guys with the tool trucks show up. They visit most shops every week at the same time. You might try eBay too.

What color would you like them to be?

The cylinder leakage test can show a leaking cylinder head gasket. If coolant is getting into the cylinder, burning it washes the cylinder clean and can lead to the spark plug insulator being a lighter color than normal.

You also have to look at fuel trim numbers on the live data display on a scanner. If they're high positive, it means the computer is seeing the need to add fuel beyond the normal calculated values. A lean condition can cause a cylinder to run hotter than normal and lead to the light-colored spark plug insulator. High negative numbers means the computer is subtracting fuel from the pre-programmed values in an effort to fix the rich condition, but perhaps without success.

Your mechanic will introduce an artificial lean and rich condition to see how the computer responds. There are many things that can cause a rich or lean condition to be detected while the opposite is occurring in the cylinder. That's why diagnostic fault codes are just the starting point. He may also short out each spark plug wire momentarily to see what effect that has on what the oxygen sensors are reporting. The problem is all of these things require a scanner to see what is taking place.

What you're using is an inexpensive code reader. Those are needed on all vehicles except Chrysler products. They just show the codes that are set and most let you erase them too. A few of the more expensive readers will access more than the Engine Computer, but I've never seen one that will access all the computers.

Scanners read codes too but that's a tiny percentage of what they can do. Displaying "live data" means showing the sensor values in real time, including during test drives. It will show which switches are pressed, which ones are released, which relays have been turned on by their computers, and things like that. Scanners are also "bidirectional" which means you can talk to the computers and make them do things. The most common examples include turning on the radiator fan, running dash gauges up and down, and turning on anything else that is run by computers now, like wipers and door locks. That feature allows you to operate circuits so you can troubleshoot them rather than having to do whatever it takes to make them turn on by themselves.

Aftermarket scanners never do all the things the manufacturers' equipment does, but it does it on a lot more brands and models. I have a Chrysler DRB3. A lot of independent shops bought them because with an extra plug-in card, they will do emissions-related stuff on all brands of cars and trucks sold in the U.S. Starting with '96 models. Still, for other brands, you need a different scanner to access all the other dozens of computers like the Air Bag Computer, Anti-lock Brake Computer, Body Computer, HVAC Computer, etc.

I wouldn't get the DRB3 because you want to be able to do more than emissions-related stuff. It depends too on how much you're going to use it. If it's just once per year, you might want to see if you can rent or borrow one from an auto parts store that borrows tools. I have the DRB3 because all of my cars are Chrysler products, and with a different plug-in card it will work on all of them back to '83 models. I actually use it most often for my relatives' Ford products which have the Check Engine light turning on three or four times per year!

I also have a Monitor 4000 for older cars. That one needs cartridges. One cartridge covers Fords, GMs, and Chryslers but it only works on cars up to 1995. It looks just like the Chrysler DRB2 because it was built by the same manufacturer.

The GM dealers used to use a Tech2 but I don't know much about them. EBay is a good place to look for all of these. Look at those the sellers list which cars and years apply. I'd avoid those who don't know or list any details. Some people just buy them from dealership auctions then resell them right away, and they don't know anything about them or if everything works.

At the school I used to work at we had a couple of Genysis scanners that the other instructor seemed to like. The last I remember hearing is you want the third version but there have surely been more updates in recent years.

If you plan on using this on newer vehicles, you'll have to consider the cost of updates. This equipment and the updates are some very high expenses repair shops have to deal with every year. If you buy a new scanner you may get free updates for a few years. When I worked for a very nice family-owned Chrysler dealership, we had the owners' approval to update any scanner anyone bought through us for free. I still get my DRB3 updated there.

Watch out for Snapon scanners if cost is a concern. They make some fine equipment but they're extremely proud of them, and charge accordingly. I have a friend who has one and he pays a couple of thousand dollars every year to keep it up-to-date. Snapon is like GM dealers; they don't do anything for free.

Another place to look is on the tool trucks. Those guys visit most shops every week at the same time. I like Mac Tools, but Matco is good too. Any mechanic at any shop can tell you on which days the guys show up, but a better alternative is to get a business card or phone number from one of them. Good mechanics invest a lot in high-end tools so the tool truck guys are always busy. They may appreciate getting a call from you first, then they'll tell you when it's a good time to stop in. Ask first to see "what's in the used drawer"? They're always trading in tools and equipment. Most mechanics don't buy their own scanners, but sometimes they'll get a trade-in from a shop owner, and sometimes they have repossessed items, especially expensive stuff. It appears to me if you see a scanner that has the Mac or Matco name on it, it's actually built by someone else and is available under that name. If you buy the Mac and Matco-branded product, you may be paying extra for the name, but you also might talk the guys into some free updates or extras.

My DRB3 has graphing, scope, pressure-sensing, and voltmeter capabilities too, but that requires buying a kit with all the leads and sensors. I don't use that stuff. I actually understand the scope more from 35 years as a tv repairman, but for anything I would do on a car, other than for demonstration and training purposes, there are usually easier ways to approach the problem. I wouldn't buy one scanner over another just because one gives you these capabilities unless you know how to make use of them.

Keep in mind too that repair shops are always having to update their equipment to stay current and sometimes they have older stuff they don't know what to do with. You might ask around if a shop has an older scanner you can take off their hands for a few bucks, or you might rent it for a while, then if you like what it can do, offer to buy it.

For my final suggestion, you might search for public auction sites. I get daily e-mails from one called "Public Surplus", or something like that. I know there's others out there. These are sites where government agencies list excess inventory for sale. I see scanners on there all the time from other technical colleges in my state, (WI). Many of them are angry after they get forced into buying from the lowest bid price, usually Snapon, then they get surprised later by the high cost of updates. It's less expensive for taxpayers to have them dump the equipment and buy a different brand than to keep paying outrageous prices for those updates. If you never plan on buying a vehicle newer than what the scanner is updated to, these might be some good choices, but be aware, again like GM, they have a lot of tricks built in to separate you from your money. In this case, suppose your scanner is only updated to 2010 and you buy a 2015 car. To get their scanners updated to 2015, they force you to buy the updates for 2011, 2012, 2013, and 2014! They won't let you skip a year. Their excuse is each update builds on something from the previous year's update. A few people have told me that is a lie perpetuated by the salesmen and if you're on friendly terms with one, they won't make you pay for all those "in-between" updates. I don't know if that's true or not, but it's sufficient reason I won't own one.

Up through 1995 every manufacturer had their own computer systems and languages, and their own proprietary diagnostic connectors. Beginning with '96 models, everything sold in the U.S. Had the "OBD2" emissions system. That's "on-board diagnostics, version 2". All makes and models use the same trapezoidal plug and the same computer language, and they all have a second oxygen sensor right behind each catalytic converter. This was an attempt to standardize things so repair shops didn't have to buy different equipment for every brand they wanted to work on.

By around 2004 the industry started switching over to the new, current "CAN BUSS" system. That's "controller area network". This is an entirely new computer language that is not compatible with your scanner. The plug is the same but that's all. This system turns everything electrical in the vehicle into a computer module. That includes the headlight switch, power window switch, etc. That makes it somewhat nicer for diagnosis, but it adds so much to the complexity that they had better give us some diagnostic capabilities with it.

Basically you're going to need a different scanner for the newer vehicle. Welcome to our world!

If you're going to stick with GM vehicles, I'd look at the Tech2 or Genysis. Look through the listings on eBay to get a feel for what different brands and models are worth and what features they have. All scanners will give you live data. That's a very small, low-level part of what they can do.