986 Forum - The Community for Porsche Boxster & Cayman Owners - View Single Post - Please confirm my diagnosis of one bad O2 sensor

Timbert · 10-02-2015, 05:17 PM

99 stock at 122k with CEL and five different O2 sensor codes. Using older Durametric 5 software and Gen 1 cable. I've read as many posts here on the problem as I could and watched the helpful fuel trim videos, but here's my readings after reconnecting the battery and starting up and getting warm for at least ten minutes when the cooling fans came on:

At idle FRA and TRA are flat at .98, .98, 0.0 and 0.0
Bank 1 O2 sensor ahead of cat voltage is flat at .43
Bank 2 O2 sensor ahead of cat voltage swings from .17 to .89 every four or five seconds.

Inducing lean by removing oil filler cap increases the revs but the O2 sensors follow the same pattern above, with bank 1 not responding at all and just holding at .43 or .45 volts

I happen to have three MAF sensors I have been swapping in and out and while at least one of them is bad, causing different fuel trim values, there is a common denominator so I want to isolate the O2 sensor problem. I did a smoke test for vacuum leaks with a DIY paint can which was a lot of fun but did not reveal any leaks that I could find on my first try.

10-02-2015, 05:17 PM	#1
Timbert Registered User Join Date: Sep 2015 Location: Phoenix Posts: 15	Please confirm my diagnosis of one bad O2 sensor 99 stock at 122k with CEL and five different O2 sensor codes. Using older Durametric 5 software and Gen 1 cable. I've read as many posts here on the problem as I could and watched the helpful fuel trim videos, but here's my readings after reconnecting the battery and starting up and getting warm for at least ten minutes when the cooling fans came on: At idle FRA and TRA are flat at .98, .98, 0.0 and 0.0 Bank 1 O2 sensor ahead of cat voltage is flat at .43 Bank 2 O2 sensor ahead of cat voltage swings from .17 to .89 every four or five seconds. Inducing lean by removing oil filler cap increases the revs but the O2 sensors follow the same pattern above, with bank 1 not responding at all and just holding at .43 or .45 volts I happen to have three MAF sensors I have been swapping in and out and while at least one of them is bad, causing different fuel trim values, there is a common denominator so I want to isolate the O2 sensor problem. I did a smoke test for vacuum leaks with a DIY paint can which was a lot of fun but did not reveal any leaks that I could find on my first try.