Yesterday I got the CEL while driving after about 45 hwy. miles. Scanner brought up P1126, which points to cyl. 4-6 running lean. The TSB has several dignostic tests which look like a lot of work and require tools I don't have. The car seems to run just fine. I'm wondering if I reconnected some stuff improperly after after doing my plug wire and last weekend my decklid shocks. I took my airbox off both times and my right muffler off for the plug wires. I wonder if I didn't seat the muffler clamp on correctly onto the cat pipe, or if I didn't get the airbox seated correctly onto the MAF. Anyway, between the work I did and the CEL coming, I probably drove 200 hwy. miles. Any ideers?

 

I would look at the O2 sensors. They are just pre and post the cat. If the post on the right is reading incorrectly, it may be leaning out that bank.

 

How does one test O2 sensors? With a voltmeter?

 

Hi Rick, You have mentioned having doubts about airbox and muffler replacement.
Airbox mal-mounted on the MAF would not run the mixture lean.
An air leak in the muffler system Will mislead the O2 sensors.
Yes the leak should be before the O2 sensors.
To check an O2 sensor, easiest is to hook a tester-reader on the car and check the O2 voltage with engine running. If sensor is dead, it gives a constant reading and doesn't fluctuate (0-1.0 volts). Normally, the reading in a functioning O2 sensor in a warm engine fluctuates between 0.60 - 0.85 volts, rapidly.

 

"An air leak in the muffler system Will mislead the O2 sensors."

I thought this at first but I was thinking of a header to head gasket leak which is quite easy to have. A leaky slipjoint between pipe and cat though? Not sure if that's likely.

Another test for O-2 sensors. If they are all accessible, switch both rights with both lefts. If the problem jumps sides, it's a bad O-2.

BTW O-2 sensors that have soot deposits don't work because the sensor material is blocked. It is often possible to revive them by heating with a propane torch until the soot disappears and then keeping the heat on for an extra 2 minutes or so.

 

Thanks guys. Will try this sometime this week or next weekend. Crazy busy until Sunday.

 

Update. I was at a PCA tech session a few weeks ago and the shop owner hooked the Porsche PST computer up to my car and went through everything. It found the code, but all the O2 sensors were getting even voltage and he said he couldn't find a problem. So he cleared the code and said if it doesn't come back on in about 200 miles, then not to worry. Well, today it came back on and it's been just about 200 miles. Now what?

 

Hi Rick - as I mentioned on dorkiphus I have the same problem. Same check of the sensor outputs, same results. Have you had the exhaust system apart?

 

I've only R&R'ed the mufflers a few times. Never the heat exchangers or cats. I was able too pull the codes this morning and got P1126 again.

 

I am breaking down and taking the car to a shop. First time she's ever gone to a shop for anything other than alignments and body work. My pride is shot.

 

Don't feel too bad, my guys checked all of the stuff listed here and more (including road tests while watching sensor outputs, etc) and still haven't figured it out - need more data.

 

Super old thread but did this ever get resolved?