Durametric fault code report incorrect?
 

I'm not sure, but I think I found an error in the Durametric software's Motronic fault code reporting. I was getting a pair of codes on a fairly regular basis. I think they happened together. As reported by Durametric 5.1.40 for my 1998 986:

P1121 Porsche fault code 430 - Throttle position sensor 1
P0160 Porsche fault code 20 - O2 sensor behind cat. conv.

But while scouring the web for possible solutions, I found a page that listed code 1121 not as a throttle position sensor error, but rather this for the pair:
P1121 Oxygen Sensor Heating 2 After Catalytic Converter - Below Lower Limit
P0160 Oxygen Sensor After Catalytic Converter (Cylinders 4 - 6) - Interruption of Signal

Now that makes more sense--nothing to do with the throttle position sensor if that's correct. All about the post-cat O2 sensor. I've replaced the sensor and await a hundred or so miles of CEL-free driving so that I can pass a smog test!

Here's the page with the info. The author is Randall who I think might be a frequenter of 986forum.
Boxster Check Engine Light Codes

the first set appears to be for DME5.2.2 and the second set is from DME 7.2 .
based on Bentley manual.
don't know when the transition took place, but isn't the 5.2for the mechanical throttle body whereas the DME 7.2 is for the electronic throttle body cars?

Oh, interesting. It didn't occur to me that the same code would have a radically different meaning depending on model year. My Durametric readout says Motronic 5.2.2, and it is a mechanical throttle body. I think MY2000 (2.7 and 3.2S) was when the change to electronic throttle occurred. It is worth noting that the throttle position sensor might be a totally different thing between mechanical and e-gas.

I didn't think to look in the Bentley manual. In my copy, it shows yet another wording of the codes, and some of them are missorted in the tables so they are easy to miss. It's like people are typing the informational strings in by hand and re-wording them as they go.... I guess I'll wait to see if any code is thrown as I put miles on this week. If not, then I might conclude that Bentley and Durametric are wrong as opposed to Renntech.

SOURCE - DME - CODE - TEXT

Durametric - 5.2.2 - P0160 - "Porsche fault code 20 - O2 sensor behind cat. conv."
Durametric - 5.2.2 - P1121 - "Porsche fault code 430 - Throttle position sensor 1"

Bentley - 5.2.2 - P0160 - "Post-catalyst oxygen sensor, cyl. 4-6"
Bentley - 5.2.2 - P1121 - "Throttle position sensor 1"
Bentley - 7.2 - P0160 - "Post-catalyst oxygen sensor, cyl. 4-6"
Bentley - 7.2 - P1121 - "Heating of post-catalyst oxygen sensor, cyl. 4-6"

Renntech - 5.2.2 - P0160 - "Oxygen Sensor After Catalytic Converter (Cylinders 4 - 6) - Interruption of Signal"
Renntech - 5.2.2 - P1121 - "Oxygen Sensor Heating 2 Behind Catalytic Converter – Below Lower Threshold"
Renntech - 7.2 - P0160 - "Oxygen sensor after TWC, bank 2"
Renntech - 7.2 - P1121 - "Throttle position sensor 1"

Randall - ? - P0160 - "Oxygen Sensor After Catalytic Converter (Cylinders 4 - 6) - Interruption of Signal"
Randall - ? - P1121 - "Oxygen Sensor Heating 2 After Catalytic Converter - Below Lower Limit"

The Mitchell OnDemand service info shows for DME 5.2.2 that P1121 is the O2 Sensor heater (bank 2) ahead of cat conv is below lower threshold. BTW, P1117 is for bank 1.

Another note that the info say s that if P0160 is stored then P1121 may also be stored.

Regards,
paul...

After replacing the secondary O2 sensor (not very difficult) and taking a few short drives over 3 days, no CEL. Then I drove it to work yesterday, intending to go get a smog certification in the afternoon. Unfortunately the CEL came back on. D'oh! But the good news is it's unrelated to the O2 sensor, it's just the P0446 EVAP code I have gotten once in a rare while. So I think the O2 sensor was indeed bad, and therefore suspect that "Throttle position sensor 1" is an incorrect label for P1121.