MAF Sensor Issues

[zegypt]

I've long had MAF Sensor issues (CEL comes on, and now ABS (failure) and PSM (turns off) lights are coming on), especially after changing out my air filter to a K & N type filter.

I have cleaned the sensor with electronics cleaner repeatedly, but over time it seems to be failing more quickly even though I suspect that the oil residue from the filter is likely not the issue anymore. The last time I cleaned it was on three days ago. There seems to have more power now, but the CEL already came back after a short period of time (although the ABS/PSM issues seem to have been alievated).

Do the sensors actually fail over time and need to be replaced, or would cleaning them always suffice? I'm reaching the point where I think I need to replace it, but I want to make sure on here first.

My car: 2002 996 with 100,000 miles.

[1999Porsche911]

I've long had MAF Sensor issues (CEL comes on, and now ABS (failure) and PSM (turns off) lights are coming on), especially after changing out my air filter to a K & N type filter.

I have cleaned the sensor with electronics cleaner repeatedly, but over time it seems to be failing more quickly even though I suspect that the oil residue from the filter is likely not the issue anymore. The last time I cleaned it was on three days ago. There seems to have more power now, but the CEL already came back after a short period of time (although the ABS/PSM issues seem to have been alievated).

Do the sensors actually fail over time and need to be replaced, or would cleaning them always suffice? I'm reaching the point where I think I need to replace it, but I want to make sure on here first.

My car: 2002 996 with 100,000 miles.

Not knowing what codes your computer is throwing, it is common and should be accepted that increasing the airflow to the engine which the K&N filter does will cause the O2 sensor to throw a code when the computer has not been properly modified. This does not mean that your O2 sensors are bad or that your MAF is bad but just that the amount of fuel mixture passing by the O2 sensors it too rich for the computer. Sensors vary in their sensitivity and can throw a code when another sensor does not. Most likely the CEL is caused by one of the sensors falling outside it's range at idle (p1123 or P1125 or both).

These codes are telling you that the exhaust has too rich of a fuel mixture and the sensor cannot reduce the amount of fuel injected enough. Most often, the codes are generated shortly after startup with throttle closed. The MAF is reading more air than is getting into the engine and therefore more fuel than needed is being injected into the engine, causing a rich condition that is being reported by the O2 sensors.

Keeping the MAF clean can sometimes maintain a better balance of fuel/air ratio, but not always. Buying a new MAF may or may not fix the problem and can even make it worse depending on the sensitivity of the new MAF.

If you insist on keeping the K&N filter, there are ways to eliminate the problem. You can install a small resistor inline on the MAF wiring harness to reduce the MAF signal which will reduce the amount of fuel injected into the engine yet maintain your current air flow. Because your stock engine is designed to run slightly rich, there is no safely issues with this and you will actually get slightly better performance from the engine. If,you want to maintain a reduced MAF signal only during closed loop operation but have the maximum signal at WOT, you can easily install a vacuum operated switch ($10.00) that will reduce the MAF signal during times there is an angine vacuum (cruising and idle) and remove the restriction of the signal when there is no vacuum. (WOT). However, maintaining a slightly lower MAF signal at all engine speeds will give you the best performance while maintaining safety in your A/F ratio.

Edited September 24, 2008 by 1999Porsche911

[wvicary]

I've done the cleaning thing of MAF loads of time and it's never lasted or even worked most times, just replace the sensor and have it done with.

[zegypt]

[if you insist on keeping the K&N filter, there are ways to eliminate the problem. You can install a small resistor inline on the MAF wiring harness to reduce the MAF signal which will reduce the amount of fuel injected into the engine yet maintain your current air flow. Because your stock engine is designed to run slightly rich, there is no safely issues with this and you will actually get slightly better performance from the engine. If,you want to maintain a reduced MAF signal only during closed loop operation but have the maximum signal at WOT, you can easily install a vacuum operated switch ($10.00) that will reduce the MAF signal during times there is an angine vacuum (cruising and idle) and remove the restriction of the signal when there is no vacuum. (WOT). However, maintaining a slightly lower MAF signal at all engine speeds will give you the best performance while maintaining safety in your A/F ratio.

Can you describe how to install a small resistor inline on the MAF wiring harness? If it isn't too much to ask, would you have a picture of it as well?

I do want to keep the increased air flow filter (it's actually made by BMC) for a couple of reasons: 1) I do feel a definite increase in power (I reinstalled the original air filter and didn't like the way the car felt), and 2) I like the sound of the engine, which is a little louder.

[bmohr]

I must be one of the lucky ones. I've had my K N air filter for over a year 15k miles and not a issue except better tone and throttle response.

[1999Porsche911]

Get your codes read first to confirm it is a rich condition at idle.

[zegypt]

Get your codes read first to confirm it is a rich condition at idle.

Trak Auto doesn't allow people to use their OBDII to check CEL's anymore, but it has been P1121 consistently in the past.

[1999Porsche911]

Get your codes read first to confirm it is a rich condition at idle.

Trak Auto doesn't allow people to use their OBDII to check CEL's anymore, but it has been P1121 consistently in the past.

Well, if that is the only code you ever get, you don't have a fuel/air problem but a heating problem with the after-cat O2 sensor on bank 2. Check the wires on the sensor and repair or replace the sensor.

Edited September 24, 2008 by 1999Porsche911

[Loren]

Get your codes read first to confirm it is a rich condition at idle.

Trak Auto doesn't allow people to use their OBDII to check CEL's anymore, but it has been P1121 consistently in the past.

P1121

Throttle position sensor 1 - signal implausible

Throttle position sensor 1 - below limit

Throttle position sensor 1 - above limit

Possible fault cause:

- Open circuit in wiring

- Short circuit in wiring

- Throttle position sensor faulty

- DME control module faulty

[1999Porsche911]

Get your codes read first to confirm it is a rich condition at idle.

Trak Auto doesn't allow people to use their OBDII to check CEL's anymore, but it has been P1121 consistently in the past.

P1121

Throttle position sensor 1 - signal implausible

Throttle position sensor 1 - below limit

Throttle position sensor 1 - above limit

Possible fault cause:

- Open circuit in wiring

- Short circuit in wiring

- Throttle position sensor faulty

- DME control module faulty

Oops. Looked at the codes for my 99 and not his 02.

[zegypt]

Get your codes read first to confirm it is a rich condition at idle.

Trak Auto doesn't allow people to use their OBDII to check CEL's anymore, but it has been P1121 consistently in the past.

Well, if that is the only code you ever get, you don't have a fuel/air problem but a heating problem with the after-cat O2 sensor on bank 2. Check the wires on the sensor and repair or replace the sensor.

Are there instructions on how to do that? Can you direct me to the right place? Thanks.

[1999Porsche911]

Get your codes read first to confirm it is a rich condition at idle.

Trak Auto doesn't allow people to use their OBDII to check CEL's anymore, but it has been P1121 consistently in the past.

Well, if that is the only code you ever get, you don't have a fuel/air problem but a heating problem with the after-cat O2 sensor on bank 2. Check the wires on the sensor and repair or replace the sensor.

Are there instructions on how to do that? Can you direct me to the right place? Thanks.

Loren corrected me above. That code is for older 996 than yours. Read his post.

[zegypt]

Get your codes read first to confirm it is a rich condition at idle.

Trak Auto doesn't allow people to use their OBDII to check CEL's anymore, but it has been P1121 consistently in the past.

P1121

Throttle position sensor 1 - signal implausible

Throttle position sensor 1 - below limit

Throttle position sensor 1 - above limit

Possible fault cause:

- Open circuit in wiring

- Short circuit in wiring

- Throttle position sensor faulty

- DME control module faulty

Hi Loren....sorry, I didn't see your post. I don't know where the wiring, throttle position sensor, or DME control module are located. Do I have to go to the dealer for this, or is this something I can do myself with some instruction? Please let me know. Thanks!

Edited September 25, 2008 by zegypt

[Loren]

Get your codes read first to confirm it is a rich condition at idle.

Trak Auto doesn't allow people to use their OBDII to check CEL's anymore, but it has been P1121 consistently in the past.

P1121

Throttle position sensor 1 - signal implausible

Throttle position sensor 1 - below limit

Throttle position sensor 1 - above limit

Possible fault cause:

- Open circuit in wiring

- Short circuit in wiring

- Throttle position sensor faulty

- DME control module faulty

Hi Loren....sorry, I didn't see your post. I don't know where the wiring, throttle position sensor, or DME control module are located. Do I have to go to the dealer for this, or is this something I can do myself with some instruction? Please let me know. Thanks!

The throttle position sensor is on the throttle body.

Well, you can check the throttle position sensor with an oscilloscope. You should get very short duration pulses every 400 microseconds (or so) at closed throttle and 100 microsecond pulses with wide open throttle.

or you could hope the wiring is okay and try a new throttle position sensor.

[gillric]

I have a 99 C2 with 52.5 K miles. I repeatidy had CEL code 1123 displayed on my laptop diagnostic software program. I replaced both oxygen sensors left bank. Still had CEL code. Replaced oil separator rubber bellows next with same results. CEL codes 1123 and 1125 started registering. I cleaned the MAF with brake cleaner same results. Replaced MAF and check engine light went out at +40 miles. The CEL has stayed off for over 100 miles now, a record, so I think the MAF was bad. In reading other forums, this sensor does go bad. It's very easy to replace, 5 mins. max. Hope this information is a help.

gillric

[zegypt]

Just to give an update, I ended up going to a local specialty car shop in West LA called Lucent Motors. The diagnostic test he ran indicated that I was having issues with my oxygen sensors, which he believed to be dirty, so he had me put a $12 can of Redline fuel system cleaner in my tank and said that should do the trick. It appears to have worked. It's been three days and I haven't had another CEL, my car seems to be running smoother with a significant increase in power. However, I did have an ABS/PSM failure again this morning, which already reset itself after stopping and starting my car again. Hopefully that will be alleviated as well.

[diego996]

I just was quoted $435.42 for a MAF for my 00C2 at Sunset Imports...does that sound right?? It's such a small part. I was speechless on the phone!

[Loren]

I just was quoted $435.42 for a MAF for my 00C2 at Sunset Imports...does that sound right?? It's such a small part. I was speechless on the phone!

US MSRP is $652.81 - so that sounds like a good deal to me.

[phillipj]

I just was quoted $435.42 for a MAF for my 00C2 at Sunset Imports...does that sound right?? It's such a small part. I was speechless on the phone!

The dreaded "Porsche Tax" :angry:

At least this site will save you so much money in the future (through advice and DIY's) you will forget about the MAF. :D

Edited February 27, 2009 by phillipj

[diego996]

I just was quoted $435.42 for a MAF for my 00C2 at Sunset Imports...does that sound right?? It's such a small part. I was speechless on the phone!

US MSRP is $652.81 - so that sounds like a good deal to me.

I saw part no. 996.606.124.00 on Pelican Parts for $252.25 is this the right part? It's made by Bosch, is that OEM?

[Loren]

I just was quoted $435.42 for a MAF for my 00C2 at Sunset Imports...does that sound right?? It's such a small part. I was speechless on the phone!

US MSRP is $652.81 - so that sounds like a good deal to me.

I saw part no. 996.606.124.00 on Pelican Parts for $252.25 is this the right part? It's made by Bosch, is that OEM?

Yes, 996.606.124.00 is correct for MY00 C2

[diego996]

I just was quoted $435.42 for a MAF for my 00C2 at Sunset Imports...does that sound right?? It's such a small part. I was speechless on the phone!

US MSRP is $652.81 - so that sounds like a good deal to me.

I saw part no. 996.606.124.00 on Pelican Parts for $252.25 is this the right part? It's made by Bosch, is that OEM?

Yes, 996.606.124.00 is correct for MY00 C2

I have only P1128 showing. I've read through the threads on the topic and I'm not ready to "throw in the towel" on air leaks and buy the MAF just yet. So I was wondering if its possible to inspect the bellows without removing the AOS on that side.

[RFM]

The AOS bellows is visible and replaceable with the AOS in place, manual transmission is easier accessible than Tiptronic.

[rb101]

I was getting 1128 and 1130 codes once every other month before I moved from NC. I replaced the bellows on the AOS 9 months ago. When I moved, my drive involved more idling at lights and it would pop these codes every two days. It would also stumble/hesitate when cold in the morning for about 30 seconds and if I would accelerate passing thru 4500rpm, the ABS and PSM lights would come one. All the posts said to replace the MAF, so I did, and all the codes disappeared. Go figure.

[Brad Roberts]

I saw part no. 996.606.124.00 on Pelican Parts for $252.25 is this the right part? It's made by Bosch, is that OEM?

Yes that is correct.. they are whoring it out at that price :) Cost is $217.10 and Bosch is OEM :)

You will end up finding out it is your MAF :) Promise.

B