CEL On, P0130, P1124, P1126

[masterbm]

Hey Friends,

I am Cincinnati's poorest, dumbest Porsche owner, and bad experiences with local mechanics have given me a vested interest in DIY Porsche repair. Now I need a little guidance. I have a 1999 2.5 Boxster (986) with just over 60,000 miles on it. Over the winter my CEL came on, and weeks to months ago, I had the thing back in the shop to find out why, and get it fixed. $300 later, the mechanic had replaced the fuel filter, cleaned out the injectors, and the CEL stayed off for about a week and a half. Meanwhile, my engine has begun to pulse as I idle between about 800 and 1000 rpms. Sometimes worse than others. This ticked me off, so I got a cheap OBD decoder, which had this to say, followed by what the code menu on this site has to say:

P0130 - Oxygen Sensor Ahead of Catalytic Converter (Cylinders 1 - 3) - Intercore Short Circuit or Limited

P1124 - Oxygen Sensing Adaptation Area 1 (Cylinders 1 - 3) - Rich Threshold

P1126 - Oxygen Sensing Adaptation Area 1 (Cylinders 4 - 6) - Rich Threshold

I have seen other similar discussions somewhere on this site, but haven't been able to find them again.

My question is this: Anybody had similar experience, and found solution? I have very little experience with these cars, so if this can be a DIY project, where can I go to get a play-by-play on how to fix this?

Thanks in advance,

Brian

[Loren]

P0130 - possible faults:

Crack in ceramic material

Reference air polluted

Short circuit in signal wire to sensor ground

P0130 - possible causes:

Oxygen sensor

Wiring harness

DME control module (intercore short circuit).

P1124 and P1126 mean that the whole engine is running lean and the DME can not compensate for it making the mixture more rich. In most cases this is caused by:

Intake air system leaking

Fuel pressure too low

Volume supply of fuel pump too low

Fuel injectors fouled (not likely since this would mean all are fouled)

I would solve the P0130 then reset the codes and see if the others still occur.

[masterbm]

P0130 - possible faults:

Crack in ceramic material

Reference air polluted

Short circuit in signal wire to sensor ground

P0130 - possible causes:

Oxygen sensor

Wiring harness

DME control module (intercore short circuit).

P1124 and P1126 mean that the whole engine is running lean and the DME can not compensate for it making the mixture more rich. In most cases this is caused by:

Intake air system leaking

Fuel pressure too low

Volume supply of fuel pump too low

Fuel injectors fouled (not likely since this would mean all are fouled)

I would solve the P0130 then reset the codes and see if the others still occur.

<{POST_SNAPBACK}>

Hmm. . .any tips on how to go about diagnosing the P0130? Is it worth it for a newbie to get a manual or equivalent product and try to proceed, or am I liable to do permanent damage? What I mean is, with some car experience, can joe average jack the car up in the garage, get to things like the 02 sensor, wiring harness, etc without specialized tools, little experience with Porsche, etc?

[Loren]

From the OBD II manual- Testing the Oxygen sensor:

1. Heat the oxygen sensors (road test car under load or run engine without load at high rpm).

2. Connect Porsche System Tester 2 or scan tool and read voltage of oxygen sensor 1 ahead of catalytic converter.

Display: Voltage fluctuations between 100 mV and 800 mV. -- Oxygen sensor OK.

If a value around 0 V is displayed, a short circuit has occurred between the signal wire and sensor ground.

3. Remove H02S connector 1 ahead of catalytic converter.

4. Connect voltmeter at sleeve to pins 3 and 4.

Display: approx. 450 mV. -- Replace oxygen sensor.

Display: approx. 0 V -- Check wiring harness.

If the wiring harness is OK, remove all oxygen sensor connectors and perform measurement to item 4 on all oxygen sensors.

[Tool Pants]

http://www.renntech.org/forums/index.php?showtopic=4331

If you have a problem with an oxygen sensor then this is an example of how valuable a PST2/PIWIS is. After Peter replaced my DME he checked the function of the 4 sensors as my other 5 fault codes were sensor related. I wish I had taken a picture of the screen. The values of all 4 sensors are displayed at the same time and there are numbers for each of the sensors. One sensor was reading below the limit and the other 3 were fine. You do not get this kind of info from a simple code reader.

The sensor that was bad had been replaced twice before. But I had to replace it again. It is easy to replace if you know you must unlock the electrical connector.

This is a pic from a tech session 2 years ago where the PST2 oxygen sensor readings were displayed on a wall so we could all see them. What I saw on the PIWIS was a bit different, but you can get the idea.

I suggest you find a shop with a PST2/PIWIS and someone who knows how to use it. Otherwise you will just be throwing parts at the car thinking it is one thing when it might be another or a combination of things.

[1999/986]

if the whole car was running lean could a failed MAF be the problem?

[Loren]

if the whole car was running lean could a failed MAF be the problem?

Some aftermarket scan tools (like mine) can also display all four sensors and the voltage readings. It is all available via OBD II if your tool supports it.

I guess the MAF could still be part of the problem - but until you fix the first O2 sensor problem you won't know. There are codes specfic to an MAF failure but you don't have those. IMHO - You need to look at the O2 voltages correct that problem then look for other causes and faults. If you have a bad O2 sensor it can mask or cause all sorts of problems/faults.

[1999/986]

There are codes specfic to an MAF failure but you don't have those.

<{POST_SNAPBACK}>

ahh..you're right. i had to replace my MAF a while back but i couldn't remember the codes off the top of my head (in fact, i'm trying to forget them). thanks for clearing that up.

[masterbm]

if the whole car was running lean could a failed MAF be the problem?

<{POST_SNAPBACK}>

The mystery deepens. . .as I was investigating this problem a few weeks ago with a buddy's OBD reader, there was an MAF-related code, as well as a throttle sensor code that appeared. Those have since disappeared. Hmm. . .

Thank you all for your time and expertise. At least I now know that this problem is very out of my league, and to ask my mechanic if he has PST2/PIWIS capability.

I'll keep you all updated!

[1999/986]

if the whole car was running lean could a failed MAF be the problem?

<{POST_SNAPBACK}>

Some aftermarket scan tools (like mine) can also display all four sensors and the voltage readings. It is all available via OBD II if your tool supports it.

I guess the MAF could still be part of the problem - but until you fix the first O2 sensor problem you won't know. There are codes specfic to an MAF failure but you don't have those. IMHO - You need to look at the O2 voltages correct that problem then look for other causes and faults. If you have a bad O2 sensor it can mask or cause all sorts of problems/faults.

<{POST_SNAPBACK}>

loren, what aftermarket scan tool do you have? how much do they cost? i'm looking to start getting some tools and such...starting with the service manuals. since masterbm gets the title of poorest and dumbest Porsche owner in cincinnati, then i get the title of poorest and dumbest in tennessee. cheers to being poor but still buying expensive toys!!!

this is off topic, but could you make a list of recommended "essential" tools for doing basic diagnostic/repair/maintenance"? or is there such a thing as "basic diagnostic/repair/maintenance" aside from an oil change?

[Loren]

I just did a review of it in the new Reviews section. You can find it here.