Looking for the last word on P1124 & P1126 fault codes
 

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Hey guys,
I have '99 Boxster with 112K and a manual tranny.
Started the car at work to come home and the CEL came on. I checked the codes and got this...
P1124 Porsche fault code - 167 Fuel pump relay final stage and...
P1126 Porsche fault code - 356 O2 sensing adaption lower load range bank 1

After searching a few web forums I'm confused! Some say it's a MAF (I guess that is Mass Air Flow?), the car is too rich vs. too lean etc... I need to hear from someone who knows what I need to do.

FYI... I've only have the car a couple of months and I've done a few little things to it like change the engine and tranny oils - and changed out a K&N air filter with OEM one (I noticed a few guys say the oil on the K&N can mess with sensors?)

Anyway - any info would be a great help! Thanks!

Joel

Well, with a K&N first thing I would do is remove MAF and clean it. I'd also revert back to the stock air cleaner/filter setup.

Over oiling the filter element will contaminate the MAF and that ain't good.

Besides the stock air filter a pretty good filter and very easy to service.

You can leave MAF installed, disconnect it from wiring harness, clear error codes, then start engine and run it, drive car, for a while and see if the P1124/P1126 error codes return. You might get a check engine light but error code will be due to disconnected MAF.

It can take considerable driving -- 30 or so miles of varied driving -- before CEL can come back on. if you can monitor long term fuel trims at the same time you can note if engine controller moving towards its enrichment limit by the long term fuel trims going higher and higher (+10 is a lot of adjustment).

Wtih MAF disconnected and the above behavior you can eliminate MAF.

If at any time you are running engine though and it starts acting up, surging at idle, smoking, or just doing anything out of the ordinary shut off engine first and ask questions later.

Anyhow, P1124 is oxygen sensing adaptation range 1 (cyls. 1-3) at enrichment limit.

P1126 is same error for cyls. 4-6.

If DTC P1124 or P1126 logged then fuel/air mixture is too lean.

Possible causes: intake system leak; fuel pressure too low; fuel injectors contaminated; volume supply of fuel pump too low.

Air leak would have to be common to both banks. One possible air leak source is the AOS. When this starts to go bad it subjects the engine crankcase to extremely low pressure which can pull in air and ultimately end up looking like an air leak at the engine. Check AOS hoses and connections for any signs of cracked or broken hoses or connections. With engine idling unscrew and remove oil tube filler cap.

While you there, also check that the cap is not leaking. A leaking cap mimiced a failing MAF to perfectly I replaced a $300+ MAF when a $13 cap was all that was needed.

Assuming the gas tank is not low then you have to check for proper fuel pressure and supply.

You can test fuel pressure at fuel rail test point and remove the fuel pump relay and bridge terminals 30 and 87 (id'd as 3 and 5 on the relay panel) with home made test harness. Fuel pump should operate and pump fuel.

Engine off pressure should be 55 +/- 3psi. Engine running 48 +/- 3psi.

Test pressure ports require new seals. Check with Porsche parts counter guy and get extra ones before you test fuel pressure.

Be careful working around running engine and testing fuel pressure and flow.

Sincerely,

Macster.

Thank you! That is a lot of really useful/helpful information! I'll do what I can but when it gets to the fuel pressure testing etc. I might have a professional do the rest. Thanks again, Joel

I had a very small air leak on the intake that cause those codes.

where exactly was the very small air leak on the intake? Thanks in advance..:bowdown:

You are probably wondering : "How do I find a vacuum leak?" Many of the helpful speculation on vacuum leaks never explains how to find them. Someone better qualified than me should write a comprehensive tutorial. As the plastics age and heat cycle this will become a more common problem?
Those of us who have tried to locate a small vac leak know how difficult,tedious and inconclusive this can be.
For example, one of the most highly regarded contributors here(not me !!) struggled to locate the culprit in a vac leak CEL code mystery.Sort version = eventually he found the base of the vacuum accumulator had a hairline crack. Finding leaks like that require a lot of dismantling and then you can't run the engine so you must generate a vacuum artificially to locate the leak .But you won't hear the hiss because of the noise of the vac pump or venturi on the compressor attachment.
I offer 3 useful tools that others can research and comment on:
1. Propane(unlit!),Brake cleaner,water to direct on suspected areas of leakage.Propane is safest but still risky for fools.
2.An Engine Ear to listen for the tell-tale hiss .Has a light on a wand and a great video linked below
3. A very small, very bright LED light array on a gooseneck - to see failed connections
Kobalt also make a smaller one.
I hope this gets you started.
But really you need a Durametric. That would give you a much sharper focus on the problem. The random hunting is not efficient
Others feel free to re-post the links and ideas.

How to find a vacuum/engine intake leak varies somewhat depending upon the engine. Used to be -- in the good old days (not!) -- there was where the carb bolted to the intake and where the intake bolted to the engine heads with one maybe 2 vacuum hoses connected to the intake.

It was easy to move the hoses about to see if the engine reacted to the hose being moved. Or often what I'd do was to just cut a new hose and install it. My auto tech buddies always had vacuum and fuel line hoses in some bulk handy and I followed their lead.

Often it was quicker to replace a suspected hose than to spend time trying find where (if) it leaked.

For the carb and intake gaskets I was taught to use an aerosol can of carb cleaner to spray at the various gasketed areas while the engine was idling. If there were a leak the engine would react and one would know that's a leak.

(Might add my tech buddies impressed upon me the importance of say installing a carb or an intake manifold to do the job right. The best intake leak to search for is *none* because one didn't screw up.)

Anyhow, I used the above aerosol can of carb cleaner technique a few times and with great success. Doing this after installing two Weber side draft carbs on my Datsun 510 engine's head really hammered home the importance of a proper intake installation.

The Boxster engine and this is true of the 996 and the 996 Turbo and well, all modern Porsche engines, there are a lot of hard to reach gasketed areas and hoses. It would be a very difficult job and one that depends too much on luck to reach in with a can of carb cleaner and keep the spray on target and not disturb even damage a vacuum hose -- or something equally important. And what to do about all the hoses? And some run from the engine to the fuel tank and some are not that accessible.

I think in this case a smoke test would probably be a good way to test for a leak.

But even this has some limits if the leak is with say the fuel tank vent/vapor recovery system. However in this case one often has an error code or two to help him narrow the search.

Certainly listening has a place. It was by sound my Boxster's leaking oil filler tube cap was discovered.

The limitation of the smoke test is visibility and the valves.
You need a powerful machine and a warm engine to push enough smoke hard enough to find a concealed small leak. That is why I use baby oil with a fragrance it it. Many of the vac lines have valves in them. Some you can operate with Durametric with KOEO.
Propane is good because it reaches areas you can't see & it is quick. Plenty of Youtube on this. The vac valves are a problem area because if the leak is the wrong side of a closed valve ....
Vacuum leak hunting is an art form - like Paintless Dent Removal.It is easy to buy the tools but a surprisingly steep learning curve to fully use them.

Tell me about it. I have codes p1124 and p1126. From under the car I saw slight trace of oil where the accordion boot of the AOS connects. I found a small slit in the boot. If this was enough to cause those codes I don't know as yet as I am waiting for a new boot and clamp to replace the old one. I had a new AOS put on by a (so called indi) a couple of months ago and found the bottom clip to be an electrical tie wrap. That's where the crack or slit was. The old saying comes in to effect here. "If you want a job doing right, do it yourself" Here is a link at Pelican DIY the AOS http://www.pelicanparts.com/techarti..._Separator.htm

My Boxster OBD2 reference is at home and I'm at the office but I believe the P1124/P1126 error codes are indicative of an air leak at low engine RPMs.

If I'm right then the slit in the AOS is exactly the problem. Regardless the boot should be replaced and properly clamped to where it connects to the AOS and the block to ensure there is no leak at the boot or at its connections.

And you need to be sure any other vacuum hoses/connections to the AOS are likewise leak free.

Once you believe you have accomplished this then clear the codes and road test the car.

OK Macster thanks for answering. You are correct in saying 1124 and 1126 are indicative to low revs. The new AOS boot is much thicker rubber than what was on there. Even without clamps I bet it is more air tight than the old one. Anyway I slipped up releasing the top clamp. I managed to get strong zip ties around top and bottom where the clamps should be. I will test it as it is for now and if the codes come up again or it leaks then I will certainly get metal clamps to take over the job. Right now I am doing an early (not intended) 90,000miles service on the car. new plugs, coils, fluids. Smoke testing, Done all kinds of work and solved the evap leaks. New SA air lines where brittle ones broke on me behind the alternator. I think I have checked every plug and valve on the car lol. Ah well I have nothing better to be doing at 75years of age. I thanks my lucky stars that I have the health and ability to be able to work on the car.

I know I am in the 986 forum and have the 996 car but the job in question is the same for both.

Oh forgot to say I put in new 02 sensors up and downstream for good measure.

Provided the error codes are the same for both models.

I used to rely upon RennTech.org for a list of error codes for the various DME versions but I just visited the site and can no longer find the link to the OBD2 error codes. (And I'm a paying member.)

You need to be sure the error codes are the same for both the Boxster and the 996. I think they are but you need to be sure.

Not all models have the same error code mapping. For example my 996 Turbo: P1124 - 167 Fuel pump relay output stage -- below limit.

Codes:

– Intake system leaking.
– Fuel pressure too low.
– Fuel injectors contaminated.
– Volume supply of fuel pump too low.