Sep 122011

As I’ve stated many times on this blog, when you own a BMW out of warranty you need to learn up on maintenance. With some research and a little effort, you can literally save hundreds of dollars on relatively simple maintenance issues.

A good example is how I recently replaced oxygen sensors on my 2002 M5. The dreaded Service Engine Soon (also known as CEL for check engine light) display had lit up on my dashboard. My code reader told me it was the left O2 sensor in front of the catalytic converter. The E39 M5 has four sensors, two pre and two post cat. So I decided it was best to replace both front sensors.

You can save big on parts before  you ever touch a wrench. The best price I could find from BMW for the sensors was $206 each. A little searching on the M5Board revealed many many owners had purchased the same exact Bosch sensor from Amazon for around $50. A really good tutorial from BimmerDIY was also very  helpful.

So right off the bat, two Bosch 13477 sensors cost me $100, rather than $400.

Old sensor top, new bottom -- exactly the same

Removed sensor

Installation took me less than an hour, and I was working very slowly and carefully. I had also purchased the open 22mm. socket from Amazon to remove the oxygen sensors themselves. The sensors plugged into a small black box on the underside of the car, held in place by two 10mm. bolts. There were two boxes, each containing pre and post sensors on that side of the car.

Sensor box

As usual, my repair was made much easier thanks to my friends at Hollin Hall Automotive lending me access to a lift. While the car was in the air, I replaced the right front plastic underbody piece I had stupidly banged up by brushing against a curb. It was one of those “hard to see but I know its there” type of repairs, and I knew it would be easy to replace.

New underbody panel

The swap was somewhat complicated by the fact that the outside temperature gauge connected into that underbody piece. I was careful with the connector and I closed off the opening with some duct tape.

Old vs. new -- note slot for sensor

New panel in place

I’d estimate that dealers would definitely would charge two hours of labor for this job, maybe even more. At $125 per hour, that’s at least $250 labor and the dealer parts cost of $400. So total of $650, vs. $100 for the sensors and my time on a Saturday morning.

So doing this job myself saved around $550. The DIY satisfaction was priceless.

  One Response to “Replacing Oxygen Sensors on an E39 M5”

  1. Thanks so much for this. I am getting an “Engine failsafe program” intermittently when I start my ’01 M5 and I think it’s the O2 sensors. I’ve already found them on Amazon but I was looking for a good tutorial on replacement. Looks pretty simple and straightforward to me. So the walkthrough that you linked to works on the M5 as well? I notice it was specifically for a 540i.


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