The diagnosis

The scanner found three codes on the CRV: P0430, P1166, and P1167.

My secret decoder ring tells me that the “P” means powertrain. The first number is either a “0″ or a “1″. Zero means it is a generic problem, and a one means it is specific to the model. My reader was no help in the Honda-specific codes, directing me to a telephone number.

I went, instead, to the web. There are several sites to help you understand the codes. I found obd-codes.com to be the most helpful. Or google “2002 Honda CRV P1166″ and you’ll find not only the problem code, but descriptions of how to repair it, and trouble spots that other DIY’ers found (and how to avoid them). By then end of a dozen clicks, I knew more about automotive emission systems than I ever though I would need to.

The P0430 code, indeed, pointed to replacing the catalytic converter, but that code (when erased) cleared and has not reappeared.

The other codes, P1166 and P1167, are both related to the oxygen sensor. This is a $150 part and it just screws into the inlet portion of the catalytic converter; hence, it requires virtually no labor. I could see my repair bill drop from $2,200 to about $300. Whew!

The key failure: Oxygen sensor

The oxygen sensor is used to measure the amount of oxygen in the exhaust. That information is fed back into the fuel injection system to determine the optimal amount of fuel and air to let in for every combustion cycle. If it’s not optimized, your gas mileage drops.

An oxygen sensor uses an oxide semiconductor (alumina, zirconia, zinc oxide,…). The oxygen ions move through the lattice carrying charge, creating an electrical current. The number of oxygen ions is proportional to the partial pressure of oxygen at the surface. Oxygen ions are really slow, so to improve the response of the sensor, they heat it up. It is the heater on the oxygen sensor that fails. This is a fairly common item to replace.

Gettin’ dirty

Just for kicks, I crawled under the car to see if I could figure out where it goes. It was a cinch to follow the exhaust pipe back to the catalytic converter. There are two thingys going into the catalytic converter. I was pretty sure it was the one on the left, since it didn’t look like original equipment, and I have had the sensor replaced before.

It looked really easy to replace. Just unplug the sensor and unscrew it. How hard could that be?

So I read some more online, and found one guy who pushed so hard on the wrench trying to get the sensor out, that he broke the wrench. Yikes! I would think if you put that much force on it, you could break the cat converter, and then I’m back to looking at a $2,200 repair — if not more.

Dealing with the repair shop

So I decided to take it to the shop. I had it replaced in about 30 minutes, but they charged me $420. Ouch! Still, better than the $2,200. But I think I might start shopping around for a new repair place.

There are two kinds of repair guys. I can imagine there are repair guys out there who would love to work with a customer who took the trouble to investigate the problem herself — like the Car Talk guys. Then there are the guys who feel threatened by that same customer — like, unfortunately, my current shop.

I’ve decided that there’s a difference between service and repair. I trust these guys to change the oil and to put on new brake pads, but I think I’ll be doing more of the diagnosing myself in the future.

How to become the most popular person in the office

I can reset engine lights. I am powerful. I am sexy. Hear me roar.

So far I’ve “fixed” cars for two colleagues. They are forever in my debt. This is always a useful thing.

Although my experience with fixing cars is extremely limited, what I’ve seen so far is that most CEL’s are caused by one-time-only problems. Reset the engine light, and it doesn’t come back on. Why I should take my car to the mechanic?

An OBD-II code reader may just be the best investment I’ve ever made.

Related Posts: How to Reset Your “Check Engine Light”: OBD-II Code Readers

Disclaimer: No position in any company mentioned in this post.

Image credits: All photos are my own.

The car:  2002 Honda CRV

It’s a 2002 Honda CRV with about 100,000 miles.  Trade-in value is about $6,000.  The Check Engine Light (CEL) came on back in November.  I took it to my mechanic, whom I’ve done business with for about three years. I’ve been pretty happy — he’s always seemed like an honest guy.  He told me it needed a new catalytic converter and oxygen sensor for a total of $2,200.  Gulp.

I told him I’d have to think about it.  He cautioned me that it wouldn’t pass emissions testing without the repairs.  Luckily, it’s not due for inspection until August, giving me nine months to figure out what to do.

Would you:

1. Put $2,200 into a seven year-old car?
2. Get another opinion?
3. Sell the car?
4. Diagnose the problem yourself?

The tool: Actron OBD-11 Code Reader

Opting for #4 might seem like do-it-yourself-brain-surgery, but it’s really not that bad.  Bring on the OBD-II code reader.  For about $50 you can buy a device that reads the same codes that the mechanic sees when he checks your engine, and ta-da! it can reset the engine light.

Every time you start your car’s engine, it does a power-on self test (POST).  The POST checks hundreds of subsystems and sensors to make sure everything is working.  If there’s a problem, the CEL lights up.  Many of these problems are intermittent or are caused by some unusual innocuous event.  The POST is smart enough that if it doesn’t see the problem again in the next several (e.g. forty) times you start the engine, it will turn off the CEL.  If the problem persists, then the CEL stays lit, and you should take action.  The car’s computers also monitor the engine while you’re driving, and error conditions can turn on the CEL, too (not just the POST).

I bought an Actron OBD-II reader for about $50 through Amazon.  There are more complicated (and expensive) readers that let you check timing and monitor signals in real-time, but I just wanted the codes.  My goal was to work better with my mechanic; I wasn’t planning to do the repair myself.

The device is simple-as-pie to use.  All cars sold in America are required to have an OBD connector.  It’s located under dash near the steering wheel.  Put the key in the ignition, turn it to “on” (don’t actually start the engine), and plug in the reader.  It will power on and start reading the codes stored in the OBD system.

Once you’re read the codes, write them down, and then press erase.  This resets the codes and turns off the CEL.  Next time you turn on the engine, if the POST finds a problem, it will turn the CEL back on.

In the next post, I’ll tell you what the scanner found and how I resolved the problem.

Related posts: How to Reset Your “Check Engine Light”: Success!

Disclaimer: No position in any company mentioned in this post.

Image credits: All photos are my own.

Carnivals: This post was included in the The Last Carnival of Personal Finance of the Year! hosted at Gather Little by Little and the 99th Money Hacks Carnival hosted at 20s Money.