Engine Check Light: P1128 & 1130
 

Hi,

I have a 2000 Boxster and I am having issues with the check Engine Light coming on. I am pulling the p1128 code and p1130 code. So have been reading forums and I have cleaned the MAF sensor and Throttle body and rest the codes. They come on after driving. Confirmed the Oil caps and gas caps are closed and the codes come back. I have replaced the MAF sensor and Oil filter , reset the codes and they still come on.

I took it to my Porsche repair guy and after a 10 min ($100) diagnostic , he said the MAF sensor is bad. I told I bought it new at Autozone. He said that it was either faulty or I didn't reset it right (which I think I did). He is charging me $400 for a new MAF sensor.

Does anyone have any advice/ suggestions. I am a little frustrated. Thanks for your help.

those codes refer to a short to battery positive on both of your post cat O2 sensors.
since it is both sensors with the same problem I would look for any fuse or relay that would affect O2 sensor function.
Then I would test the sensors
then look for a wiring issue
then look to a bad DME

I think the info in this post on Renntech is more accurate:
https://www.renntech.org/topic/32802-error-codes-p1128-and-p1130/

Lean condition detected by the primary O2 sensors that cannot be corrected by the DME.
Think: Too much air, or not enough fuel, or sensors on either end (MAF or O2) are reading incorrectly.

and here's a pic that was posted on Rennlist:
https://rennlist.com/forums/attachme...nion-p1128.jpg

...not that I'm particularly smart on this, but I've been dealing with it intermittently over the last month on one of my cars.

Either not enough fuel or too much air.

Pressure test the fuel pump. Replace the fuel filter.

Then check for air leaks in the intake system.

[QUOTE=78F350;600925]I think the info in this post on Renntech is more accurate:
https://www.renntech.org/topic/32802-error-codes-p1128-and-p1130/

Lean condition detected by the primary O2 sensors that cannot be corrected by the DME.
Think: Too much air, or not enough fuel, or sensors on either end (MAF or O2) are reading incorrectly.

and here's a pic that was posted on Rennlist:
https://rennlist.com/forums/attachme...nion-p1128.jpg

...not that I'm particularly smart on this, but I've been dealing with it intermittently over the last month on one of my cars.[/QU


I just looked up the codes in the Bentley manual and relayed them in my post. With the Bentley saying "short to battery positive" I would still check the things I listed in my post to the OP. If all was ok I would then look to the to much air not enough fuel scenario. As the Bentley states the system is calling for enrichment beyond the upper limits of the system. Vacuum test for excess air in the intake. exhaust leaks ahead of the O2 sensors. If all ok then on to fuel issues.

I had these two codes in the past.

http://986forum.com/forums/boxster-general-discussions/72288-p1128-p1130-running-fine-turned-into-barely-running-engine.html

The short version is I had a bad MAF. To get to that conclusion I ended up monitoring the fuel trims. A Durametric or other scan tool that can read fuel trims values will tell you if have a vacuum leak or not. If you can determine if you have a vacuum leak or not then you can focus on either fuel or air as thstone suggested.

What brand of MAF did you buy? You may have gotten a bad or cheap one?

The general consensus I found online was it should be Bosch. If I remember right the Porsche branded MAF sensors are Bosch with a Porsche stamp. Some on the forums state that Porsche hand picks the betters MAFs from the lot for the Porsche branded ones. I can’t confirm or deny this. The moral of this story is maybe you Autozone MAF may be bad out of the box. It wouldn't be the first time a new sensor failed.

$400 to change a MAF is way too high in my opinion. The sensor is about $200 bucks for a Bosch. It takes longer to get to the engine then it does to change the sensor.

What he said . . . . . . Changing the MAF is a 10 minute DIY. Just need the proper tamper proof torx socket.

When I had the issue with bad MAF sensor, I didn't buy a new one. It's crazy expensive. I purchased a used MAF sensor making sure it was the latest revision. It's the Bosch 98660612501 a few years back. There might be a new revision out but that was the latest one for my 01 at that time. I bought it off eBay and the seller was (qualityporscheparts) who I have had good luck with several times.

I tried cleaning the MAF sensor & throttle body like you with CRC products but CEL came back on after a quick drive. It cost me $40 and it's been running great since. I'm not sure that it matters but the used MAF sesnor was listed with around 30K miles of usage at the time.

Changing the MAF sensor requires you to have a security torx bit. I had to buy a cheap set on eBay that cost like $8. It came with magnetic security torx bits among other bits that are not common. I don't recall resetting anything but if I did, I used a cheap OBD2 bluetooth with TorquePro smartphone app. It's a very easy job like paulofto said. You just have to put your softtop in service mode and get access to the engine. You will see it.

I've had so much bad luck with Auto Zone parts that I refuse to go there anymore unless the closest NAPA or Advance Auto is 100 miles away. Or if it can wait, I'll order the part online.

I changed the MAF with a OEM Bosch MAF sensor and after clearing the codes. They came back. So I am back to the drawing board.

Aos
 

Check your Air Oil Separator. Remove the oil fill cap while the engine is running. Is the cap hard to remove? Is there a lot of vacuum from the oil fill tube (does it sound like a shop vac)?

I have recently come up with both codes. Used to get only one every few months or so but now both codes after one day of driving. Haven't really dove into it yet.

Watching this to see how it goes.

Update: My P1128 and P1130 codes were related to a vacuum leak. Turned out it was a cracked dipstick tube. Replaced it and no more codes.

Awesome! Gotta love those simple fixes!:)

But I'm wondering how a broken dipstick tube would cause a lean mixture.