Trying to complete a drive cycle to set flags so I can get new tags (way out of date),
and I get a CEL. Figured no big deal,as this is a newly rebuilt engine,so I was expecting a bump or two. I am puzzled by 4 O2 codes. (131,151,137,157) I had thought I might get a code on the post cat due to running a 200 cell sport cat.
Checked to make sure the o2 sensors are hooked up correct (black pre and grey post)
No apparently loose vacuum lines.

What am I missing, or what should I be looking for? Thanks for any ideas.


Emerald

 

I searched,and found where a member called Amfab had an issue with the same 4 codes,but he failed to post how it was resolved,and his PM's are full.
I might have to post to his thread as well when I resolve the issue so the info will be out there for the next person needing it.

Emerald

 

If the 993 codes are the same as the Boxster, they look like

P0131 Oxygen Sensor Ahead of Catalytic Converter (Cylinders 1 - 3) - Signal Wire Short Circuit to Ground or Incorrect
P0137 Oxygen Sensor After Catalytic Converter (Cylinders 1 - 3) - Signal Wire Short Circuit to Ground or Incorrect

P0151 Oxygen Sensor Ahead of Catalytic Converter (Cylinders 4 - 6) - Signal Wire Short Circuit to Ground or Incorrect
P0157 Oxygen Sensor After Catalytic Converter (Cylinders 4 - 6) - Signal Wire Short Circuit to Ground or Incorrect

I found these at http://boxster.wikia.com/wiki/CEL_Error_Codes

Do you have an OBD reader that will monitor live data?
It would be really good to see what your pre and post cat sensors are reporting when your engine is running.

Pre-cat, I usually see oscillation between .04 and .85 volts at a frequency on the order of once per second.
Post-cat, I commonly see .625 volts. Not unusual to see it vary, but not oscillating like the pre-cat sensors.

If the pre-cat sensors are not giving reasonable data, then the engine is not running in closed loop mode.
How does the engine run? Is it running rich?

 

If anyone else is interested, the thread that e3photo is referring to is at https://rennlist.com/forums/993-foru...g-me-nuts.html

 

P0131
P0137
P0151
P0157

 

You could try bumping the thread, he or someone else with the issue might have subscribed to it meaning he'll get an email. PM the 'other' person in that thread who had the same issue?

 

Thanks for the great info guys. It looks like I need to take it to my mechanic friend,and plug in his reader. I just have a simple one,and it looks like the live data could be very useful.
We have lousy weather today,so maybe tomorrow.
I will report back with the results.


Thanks again,
Emerald

 

Oh, and the engine seems to running pretty smooth.


Emerald

 

Well I think I may have solved the problem. I spent some time under the car, and noticed that the position of the left sport cat was off a bit,and this pushed the O2 sensor tight against the heater tube. There was exposed wire , so I imagine this caused the short, which caused codes for all sensors to show.
I may try and fix the wire,or just go ahead and replace the O2 sensor.

I'll update in a day or two.

 

Did you read the P0131 diagnostice that Jason posted? I am assuming so.

Per the diagnostic sheet, the one short could cause the other fault codes...

You may very well have solved your problem...You can check your voltages at that O2 sensor after electrical taping the wire. If it were me, I'd do a visual and voltage inspection of all the O2 sensors while under the car...

If the readings are in spec, and there are no other issues present; your drive cycle may be ready to be ran.

 

Yes. I did read the info that Jason posted. I found it interesting that one sensor will trip all 4 codes, so I was confident that the problem I found might resolve things.
I fixed the wire with some liquid tape,and did a visual inspection of everything.

I cleared the codes and went for a drive cycle. The flags didn't set,but I didn't get a CEL either. I will try another drive cycle tomorrow.


Regards,
Emerald

 

Emerald,
Good find. Now stop hitting your thumb with a hammer.



Andreas

 

 

Glad you found the likely culprit. If that's not the problem, looking at the fuel trim via live data will help track the problem. One potential alternative cause could be the MAF. A faulty MAF could affect the mixture enough that the O2 sensors can't compensate. When this happens you may get an 02 code (or several) and not always get a MAF code.

Cheers
Joe

 

Thanks Joe,

I will keep an eye on it. I just cleaned the MAF, so hopefully it won't cause a problem.


Emerald