Why you shouldn't trust the CEL scan tools at Autozone

[Eikon]

So I got a check engine light a week ago. I went to autozone to have them hook up the scan tool for me (A very nice free service). The guy even printed out the diagnostic for me.

P0037 - "heated 02 sensor bank 2 sensor 1" (WRONG as you'll find out in a minute).

So I bought at 02 sensor (cheap wire-it-yourself from ebay). I chopped the harness below the blue connector on the front of the motor. I spliced the new 02 sensor in and installed it and thought I was fine.

In the meantime I decided that I was tired of going to autozone for the code reading and found a nice one on amazon.com that I ordered.

It came today..

I cleared the codes and went for a drive.. .NUTS... 15 minutes later I had a check engine light again.

I got back home, checked the codes...

P0037P0154P1168

So my codes are having babies now.

This code reader asks you to type in the make of the car before giving you the diagnostic on each code.

This time I got:P0037 - 02 heater bank 1 sensor 2. P0154 - 02 sensor bank 2 sensor 1. P1168 - Closed loop bank 2.

So what happened???

Well, I had bad info on the code and didn't do my homework properly. P0037 is actually bank 1 sensor 2.. But the code and printout I got at autozone had it flipped.. said it was bank 2 sensor 1. So I ripped out a perfectly good 02 sensor and replaced it incorrectly. My ebay special was a 4 wire and the sensor i replaced was a 3 wire.. I thought I wired it correctly, but didn't. The P1168 should go away on it's own since the closed loop diagnostic requires the 02 sensor to work properly.

It'll be fine when I'm done... the P0037 is a 4 wire sensor and will work perfectly with the ebay sensor I bought. I'll rewire the one I took off the car... thankfullly I didn't throw it away.. I've learned that much in my days of wrenching on cars.. lol.

So, the moral of the story. If you get your check engine code read at a car parts store.. it would be wise to double check the code in the FSM from Nissan to be sure of the proper description. If you have the money... it is awesome to have your own code reader.

[MinisterofDOOM]

That's why we have these threads:

Third gen CEL codes (OBD1)4th Gen CEL codes5th gen CEL codes

Always quickly accessible through the FAQ sticky.

[loystock]

It takes courage to admit a mistake, especially given his position in the forum. I applaud him for that. I wish everyone would do the same. The truth may hurt but it will set you free.

[Eikon]

lol.. I think you'll find that I'm the least proud amateur mechanic on this forum.. I am constantly learning from experience and my mistakes. So I figure I might as well share my screw ups with the forum so that others can learn from them also.

[Warped161]

Autozone will give you the right code but they have a crap definition database.

[NutriaforBreakfast]

I had to get my own code readerEverytime I went to get mine checked somewhere theywouldnt believe the 95 Nissan used a OBD2 rather thanan OBD1

[nafddur]

I had to get my own code readerEverytime I went to get mine checked somewhere theywouldnt believe the 95 Nissan used a OBD2 rather thanan OBD1

Why would you use a code reader or, worse yet, take your 95 Maxima anywhere to get the codes read? Just switch (using a small screwdriver, of course) the ECM into the test mode and read the codes out yourself in your own garage.

I've been doing that for years on my 95 Max. By the time you can get into your car and get to the end of your driveway, I can retrieve the codes myself.

[NutriaforBreakfast]

Too much trouble dealing with flashing lights at various intervalsJust want to geter done

[fiveliterbeater]

i also should add that another good reason not to trust autozone's DIY diagnostic tool is that people sometimes forget that an experienced mechanic can not only tell you what that code means but always tell you "why" it came on. anyone can replace a sensor or fix a misfire etc, but figuring out why it failed so that the problem doesnt return takes another set of knowledge skills.

[The Siath]

Autozone will give you the right code but they have a crap definition database.

+1 - get their codes - and look in the manual for the proper explanation.