Check Engine Light / Various OBD II Codes

[stphnsns]

Hi, I have a '97 2.5 Boxster with 115K miles and I recently (per OBD II diagnosis) replaced my mass air flow sensor. My c.e. light went off for a short time. Now it's back on, and the generic OBD II says, O2 sensor and then goes through every cylinder and indicates mis-fire :( A couple of questions:

Does anyone know what could be causing these readings? Or do i suddenly have a bunch of problems? Plugs?

Are they fixables for a willing d.i.y'er? If not what will I be getting into at the dealer? I live an hour from the closest dealer, so even getting to them for diagnosis would be troubling!

I haven't had the car long, and don't have a lot of money to dump into it (there's suddenly a VERY needy '85 944 in my garage too! - wifes gonna kill me). I do have a local shop that can service, but they don't have Porsche Diagnostics.

Confused, frustrated and wondering if I should of stuck to the air cooled ones...Help!

PS - While I retrieve the codes from my local auto parts store, another question: It looks like maybe I need plugs and perhaps an oil separator. Are these very complicated jobs on this mid-engined classic? Thanks again!!!

Edited February 19, 2004 by stphnsns

[Loren]

And the OBD II error codes are?

You can get these with any scan tool. Some auto parts stores will read your codes for free too.

[stphnsns]

Hi, Thanks for the help! Oddly, When I last had the car read (week or so ago), there were numerous error codes (11 I think?). They included the O2 sensor and cylinder mis-fire messages I spoke of in my previous post. He erased them (mistake?). I just went and had them read again today, so I could record them, and there were only two this time: P1124 & P1126, both indicating "Central Fuel Air Metering" as the problem. But those are the only listed faults now. Could the others return with time? What are these indicative of. Finally, with 115K miles, could new plugs help and be in order for me? Thought maybe they'd help the misfire situation, and perhaps the smoking at start-up too. Thanks SO much for your advice!!! D. Reynolds

[Tool Pants]

If a fault has been erased it will only come back if the fault is detected again.

1124 is for cylinders 1-3 and 1126 is for 4-6. The oxygen sensors are detecting a lean condition. The book lists several causes but I would check everything to see if there is a leak in the air intake. Jeff

[Loren]

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

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

The ODB II manual says that these codes indicate your fuel mixture is too lean. That is, the DME can not make the mixture rich enough - i.e. rich theshold exceeded.

It lists as probable cause:

Intake air system leaking.

Fuel pressure too low.

Fuel pump volume too low.

Fouled fuel injectors.

There is a TSB 4/00 03.. Oil Filler Cap (dated 3-24-2000) that states: "If the oil filler cap is not fully engaged, or is tilted, (not engaged on both sides) the filler cap o-ring will not provide a complete seal. This can cause a CE light and Pcodes: P1124, P1126, P1127, P1128." This would be my first try.

If that is not it. You can likely rule out the last one (since you got codes for both sides) - as a having a fouled fuel injector on each side of the engine is very unlikely.

I would look for loose or worn vacuum hoses or other manifold leaks. You might also replace your fuel filter if you have not replaced it in the last 30,000 miles.

[stphnsns]

Hi, you have been so helpful, I hope I'm not wearing out my welcome, but a couple of additional questions, from a novice:

1. Ordered a fuel filter for my '97 2.5 today, just wondering if there were any tips, instructions or diagrams available to help me install it ! I'm not sure where it's located!

2. Have been told (by PCA website) that perhaps a new vapor seporator would help with the extensive smoking at start-up that I get continually. Was wondering what kind of expense and job that would be to either a.) buy and install or have my mechanic (an non-dealer Porsche specialist) do. Car is going to him next week anyway.

Thank you SO much for all of the advice!!! D. Reynolds

[Tool Pants]

http://www.renntech.org/forums/index.php?s...st=0entry5143

[stphnsns]

Thanks! Could I possibly need a new oxygen sensor too? Where are those located? Also, I just received my fuel filter, it's # 996 110 253 52. Is that the right part number? Thank you guys, so much for all your help with my pesky questions!!! D. Reynolds

[Tool Pants]

There are 2 sensors on each side. One before and the other after the cat.

That is the correct part for the filter. Should look like this.

[BryanJ]

Didn't want to let this die without finding out if the problem was solved as I have and am experiencing a similar problem.

I have a 99 Boxster I purchased in January of '03. I experience the P1124/1126 error codes and power loss problems. I eventually changed the MAF and all four O2 sensors with my 'shoot-from-the-hip' diagnosing over the summer. Everything seemed fine throughout winter with no CEL until the beginning of this month.

Now I have on several occasions received the 1124/1126 and 1123/1125 error codes. On top of that, the car seems to have trouble starting (not all the time) but idles fine once it stablizes (which it also did last year). I have recently received error code P0455 which is described by my code reader software as 'Evaporative Emmision Control System Leak Detected (Gross Leak)'.

Also, it seems to only set the error codes only after the car is at normal operating temperature and at idle.

Anyone have any ideas?

Thanks,

Bryan

[stphnsns]

Bryan: hi, are you by chance the person who emailed me a couple of weeks ago on this topic? If so, I owe you a huge apology! I was traveling when I got the email, and it was deleted before I returned home. So, sorry!!

Anyway, that problem sounds familiar and similar to some of mine. After changing the mass airflow, my idle did stabalize for a while, but then began wanting to die occasionally upon engaging the clutch. Some one told me (or I read) that there is a strange tie in to the cooling system, and to try turning off the air!?! That did the trick for a while. Now, it's begun happening again occasionally, interestingly, it's happened right after I reset the obd codes for the C.E. light. I don't know if this is coincidence or not!?! So anyway, try some different settings on the heat/cool setting, specifically turning off the Automatic setting, and see what happens. Let me know, as I am curoius too.

By the way, did you do your work yourself? I'm getting an oxygen sensor code now. Say's I just need one of the 4. Just wondering what kind of job it is for an idiot like me. I've done one on an old 911, but that's much different. Also, does your car smoke at start up? Mine does, and I wonder if it could all be related. Was told to try a vapor seperator, but don't know. getting tired of putting money in this one! Anyway, sorry fot the delay in response, and I hope this helps! D. Reynolds

[BryanJ]

stphnsns: No that wasn't me.

If I were you I would hold off on replacing any O2 sensor. These codes are triggered by their readings and not necessarily by their malfunction. Also, hold onto your old MAF as I don't think the problem is there either. The generic error codes and some of the past advice I've received can be misleading.

I just found the OBD-II codes on this site. It states that 'P0455 = Fuel Tank Ventilation System (Major Leak) - Below Lower Limit'. Also, looking through old data logs from my car I did notice I had a 'P0446 = EVAP Canister Shutoff Valve (Function) - Below Lower Limit' trigger before as well.

P1126 seems to be the most popular code I get but recently it has listed alternately with P0446.

Some parameters when I received a P1126:

Engine Speed......763RPM

Engine Coolant Temperature......194.0 F

Short-Term Fuel Trim (Bank 1)......-2.34%

Short-Term Fuel Trim (Bank 2)......1.56%

Long-Term Fuel Trim (Bank 1)......-3.13%

Long-Term Fuel Trim (Bank 2)......-2.34%

Closed Loop; using oxygen sensor(s) as feedback for fuel control.

----------

Engine Speed......763RPM

Engine Coolant Temperature......195.8 F

Short-Term Fuel Trim (Bank 1)......-2.34%

Short-Term Fuel Trim (Bank 2)......0.78%

Long-Term Fuel Trim (Bank 1)......17.19%

Long-Term Fuel Trim (Bank 2)......16.41%

Closed Loop; using oxygen sensor(s) as feedback for fuel control.

----------

Just noticed some other codes I have received as well with data

P1128 = Oxygen Sensing Adaptation Area 2 (Cylinders 1 - 3) - Rich Threshold

P1130= Oxygen Sensing Adaptation Area 2 (Cylinders 4 - 6) - Rich Threshold

Short-Term Fuel Trim (Bank 1)......6.25%

Short-Term Fuel Trim (Bank 2)......3.91%

Long-Term Fuel Trim (Bank 1)......29.69%

Long-Term Fuel Trim (Bank 2)......28.13%

[BryanJ]

stphnsns,

To answer the rest of your questions....

Yes, I do the work myself. No dealer for 150 miles and I don't trust the local independant as he told me he didn't consider the Boxster to be a 'real' Porsche.

As far as changing the O2 sensors, it is a tight fit. Probably the hardest part is connecting the wires. Have to go through the trunk to do the rear sensors and under the car for the foward two (must easier access).

Yes, my car does smoke upon startup on occasion, about 5% of the time. Pretty much normal as my VW does as well from time to time.

[openwater]

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

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

The ODB II manual says that these codes indicate your fuel mixture is too lean. That is, the DME can not make the mixture rich enough - i.e. rich theshold exceeded.

It lists as probable cause:

Intake air system leaking.

Fuel pressure too low.

Fuel pump volume too low.

Fouled fuel injectors.

There is a TSB 4/00 03.. Oil Filler Cap (dated 3-24-2000) that states: "If the oil filler cap is not fully engaged, or is tilted, (not engaged on both sides) the filler cap o-ring will not provide a complete seal. This can cause a CE light and Pcodes: P1124, P1126, P1127, P1128." This would be my first try.

If that is not it. You can likely rule out the last one  (since you got codes for both sides) - as a having a fouled fuel injector on each side of the engine is very unlikely.

I would look for loose or worn vacuum hoses or other manifold leaks. You might also replace your fuel filter if you have not replaced it in the last 30,000 miles.

I'm getting a 1128 and 1130 on my '99 w/ 56k miles... What is 'Area 2'? Am I looking at different conditions than the 'Area 1' fault noted above? Should I do the 'Carb Spray' test? If so, where do I spray it? If the oil filler system has a leak will the RPMs jump when the spray is in proximity to that type of leak also? Thanks!

[vrauba]

Dear openwater and everybody else, I've gone thru the strings of replies to this OBD II question and can't seem to find an answer. I too have two error codes: P1128 and P1130. Did you get a response on how to fix this problem? Car seems to run fine...gas mileage is good, acceleration is good, smokes for a second on start-up, but that's it. If it's running too rich or too lean, how does one fix these? Or is it a bad oxygen sensor (which one)? Vacuum leak? The car is a 2000 Boxster with only 13K miles. Could it simply be bad gas (not me, the fuel in the car)? I checked the fuel cap, it's tight and I got a fresh tank of gas. Should I simply not worry about it and clear the fault messages off the computer, get that pesky "check engine" light off my dash, and merrily be on my way? Or do I need to fix something before it does some real damage.

[Jeremy Cottrell]

Sorry to resurect an old thread, I know that it is in poor taste, however, have we made any progress getting rid of the 1124/1126 code?

[Krsco]

Don't be sorry about keeping this thread alive. I need to know as well! My situation is mysterious and amusing. I've been driving my '97 2.5 for a solid year with the CEL illuminated and an 1125 error code. The car drives perfectly. No rough starts, no smoke, no loss of power. It's perfect! My mechanic has already cleaned the AMS, which didn't kill the CEL, and he is dying to replace it. I told him "no way." I refuse to believe that anything serious is wrong.

In the absense of any performance problems, what do you think my 1125 code means?

[aak5454]

Like many of the folks posting here, I also have P1124/P1126 always together, but never anything else. My car is '97 2.5 with 95k miles. Recently I am going them more often which made me think something is starting to fail but after reviewing the all the psot one this site I have procrastated about starting the swap-a-part process. I have only had the car about 9 months and its SEEMS to happen more often on warm/hot days (summertime now in LA; plenty hot! so happens every few days) Also, I do a lot of driving in stop-n-go travel (life in the big city :D )

Both my mechanic and I have gone over the car and not found the problem.

Area 1 is for idle and Area 2 for higher RPM range (as I have been told).

P1125 is the opposite problem as it indicates running too rich (check other post on this website for more details).

Let's keep talking about this.

[porscherescuer]

Any update on the 1124/1126 codes? Surely someone has had this fixed since 2005.

Edited July 21, 2011 by porscherescuer