Error codes after replacing O2 and MAF sensors
 

Hi, I still get the following 4 codes after replacing all 4 O2 sensors and the MAF sensor:

P0151
P0131
P0157
P0137

After replacing all 4 O2's, I took for a test drive and the water pump failed. After getting towed to the dealer, they told me the MAF sensor was faulty. I just replaced it and I still get the 4 codes above.

Any recommendations on next steps?

Thanks,
David

Car spec
 

The car relating to the post below is a 98 base 2.5

If a Porsche dealer did the work then I would take the car back to them and have them sort it out.

If that is not possible then I would disconnect the battery to let the DME re-learn the MAF settings and see if it still throws codes after that.

I’m not surprised; all four codes are indicative of all four o2 sensors being shorted to ground, which usually points to a wiring issue, not the sensors themselves. And none of these codes point to anything to do with the MAF.

When one O2 sensor throws a code, the first thing you should do is test the electrical diagnostics of the sensor, which requires about 5 min. and a digital multi meter to test voltage, continuity, etc.; the sensor does not even have to be removed to do this.

When all four O2 sensors throw the same codes at the same time, you need to be circumspect; the probability of all four dying the same way and the same time is lower than wining the lottery, it just does not happen; something else is involved. In this case, either the wiring or the DME have a problem; changing out about a grand’s worth of parts is not going to change that fact; you need to look further……………

Did you clear the codes after you replaced the MAF? If not, then the same codes indicating that the MAF is failing were still stored in the copmputer when the you took the car for a test drive (when the water pump failed).

As landrovered suggested, clear the codes using a scan tool or disconnecting the battery and then drive it and see if the codes come back. If so, post again here and someone will suggest the next steps.

Thanks for the guidance..going to need more I'm afraid. I still have the same 4 codes re-appear after disconnecting the battery and driving 10 miles. Any tips for testing the wiring that may short all 4 sensors? Im prepared to invest in the durametric tool before taking back to the dealer. I replaced the maf and o2 sensors myself as the dealer charged me 1200 for the water pump, coolant, belt and oil change. :mad:

The sensors I got off eBay were marked compatible with my 98 base 2.5 but I think I read elsewhere that the generics may be problematic with the 2.5. I would like to hear if anyone else has verified that as a problem.

Also, I heard from the previous owner that the air oil seperator was replaced about a year ago so it has been running with the cel light on for some time...though I know he only drove it sparingly as he couldn't get the top down due to a micro switch I fixed for him.

The Durametric system should be able to read the sensor values in real time if you have one. Without one, you are going to have to test one sensor, doesn't matter which one as they are all throwing the same code, to confirm it is OK. This only requires a volt-ohm meter and access to the diagnostics tree for testing a sensor for voltage, ground source and continuity. If it passes muster, you then need to start checking the wiring from each sensor back to the DME for damage, shorts, loose or damaged connectors, etc. Then test each circuit from each of the four senor ends to the DME connector pin for resistance, continuity, shorts, correct voltages, etc.

"The sensors I got off eBay were marked compatible with my 98 base 2.5 but I think I read elsewhere that the generics may be problematic with the 2.5. I would like to hear if anyone else has verified that as a problem. "

Ding Ding Ding we have a winner! Yes generic ebay sensors are well known for connection and mis-wire problems. Start there :)

That is encouraging info about the generics. I am guessing I should disconnect each sensor and test for a short to ground on each wire, though I am surprised that one short on one sensor would trigger a code on all four. I'll get the ohm meter out tomorrow.

It is more than one wire as each sensor sees its own short individually (each sensor is an individual circuit), all four sensors are shorted, hence the four codes, one for each short.

The generics were the culprit. Replaced all 4 with Bosch replacement from rockauto for 90 bucks a piece.

I'll try contacting the eBay seller regarding is advert that his sensors work on my 98 base. Wasted $160 though I'm happy that the CEL light has gone... Having the state inspection done as I type.

Thanks for all the help...this board certainly outperforms the car ;)