Hey guys,

My CEL light came on shortly after putting on a Cargraphic export loud exhaust I recently purchased used from Nick at the Speed Gallery.
My 02 X50 has 8k miles and no other engine mods. I had it reset, but after a few miles of driving the next day, the CEL came back.

Ron (vipertestarossa) at Forest Hill has been so kind to help me diagnose via email. With a "P0420" code, either the 02 sensors are inverted or I have a bad CAT. I checked the 02 sensors and they are in proper order and on tight.
MAF is fine too.

I love the exhaust! it sounds awesome and the car runs fine though. what should I do? any remedies? I was thinking of just buying a cheap OBD scanner and just reset the CEL when it comes on. but I dont think this is a good idea. I want to keep the exhaust. I did contact Nick at the Speed Gallery, he said worse case, Cargraphic would warranty it...I hate to think I have to unistall, install stock, unistall stock, then install the cargraphic again.
so much for saving money buying used.

amazing how a little yellow light on the dash can bug the **** out of me.

 

Double check the O2 sensors, I had exactly the same problem, when I stupidly switched the sensors when I swapped to my Miltek. You need to check the part numbers for each one, don't go by the connectors which is what I did...my mistake.

It would help if you knew which side the code was coming from... Follow the cables back from each sensor on each side and see that they are indeed the same and in the same order on each side...

 

02 sensor placement:the rear most sensor on each side of the car will have a grey sheeth over the wiring harness. The front most sensors will have a black sheeth over the harness. Or...the 5 wire 02 sensor goes before the cat and the 4 wire 02 sensor after the cat on both sides.

I did check this, and it is properly installed and on tight. I will crawl under the car again and check.

 

Just askin...its just a bloody pain dropping all that stuff if it is indeed an O2, I hope it is so you don't need a new Cat!

 

Sorry Ben, I didnt mean to come off sarcastically. I do very much appreciate the advice. trust me, I checked like a dozen times under the car .

I think Ive got a bad CAT.

 

Probably a MAF if the sensors are not swapped out. Not likely the cat. I was getting the same error on both cats on my Remus, it was the MAF. I trust Speed Gallery with everything.

Remember, It's almost always the MAF.

 

No worries Bud... I hope it's something easy and cheap.

Cheers,

Ben

 

02 sensors for sure...

 

so if the 02 sensors are in the proper place, should i just then get new 02 sensors and a new MAF? This is gonna get expensive? Do you always have to put new 02 sensors and MAF when putting on an aftermarket exhaust?

 

Prob the same info you all ready have but here is what alldata states


P0420 - TWC CONVERSION, BANK 1 ABOVE LIMIT

Diagnosis conditions

• TWC temperature 420 - 600 °C
• 85 seconds within rpm/load range (cumulative)
• EVAP canister burden < 8
• Speed 1280-2440 rpm
• 20 - 40% engine load (relative air charge)
• Oxygen sensing ahead of TWC is active
• Oxygen sensing after TWC ready for operation
• Engine starting temperature > -20 °C
• No faults in memory

Possible fault cause

• Oxygen sensor ahead of and after TWC exchanged
• Valve lift fault
• Aged oxygen sensor after TWC
• TWC faulty

Diagnosis/Troubleshooting

NOTE: If an aging oxygen sensor is recorded in conjunction with a fault in the TWC, a check must be performed with a new oxygen sensor to see whether a TWC fault is still indicated.

Steps 1 - 3