Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
Hey rick! An exhaust leak ahead of the downstream O2 can absolutely cause it to read lean. For our info, how big a leak are we talking about? Big ol' hole in the pipe, or just a leaking gasket?
Is there a code or symptom you're concerned about, regarding the O2 function?
Hey thanks for response, it was a pontiac vibe with the toyota engine and it had a lean code and i noticed the exhaust leak was driving that rear 02 lean, the leak was pretty big hole in front of the cat, but it also had a dirty maf that was cause the lean condition. I used the techniques taught by danner to make sure the 02 was doing its job and it was. But its wierd the moniters all set and no dtcs came back. My question now would be if that 02 is reading lean from the exhaust leak how come it didnt throw a code for 02?
rick.urso wrote: Hey thanks for response, it was a pontiac vibe with the toyota engine and it had a lean code and i noticed the exhaust leak was driving that rear 02 lean, the leak was pretty big hole in front of the cat, but it also had a dirty maf that was cause the lean condition. I used the techniques taught by danner to make sure the 02 was doing its job and it was. But its wierd the moniters all set and no dtcs came back. My question now would be if that 02 is reading lean from the exhaust leak how come it didnt throw a code for 02?
:lol: Good question! But really, my experience has shown that most vehicles are not as sensitive to exhaust leaks as they're made out to be, and sometimes depends on the make/model. I've personally seen many vehicles like yours with raging exhaust leaks and happy monitors.
How? I think it comes down to that vehicles fault detection strategy. Some are happy if there's two working O2's and something like a catalyst between them, and others code for pinhole leaks. Chrysler products, I find, are especially sensitive. The OE leak testing method involves pressurizing the exhaust to 5 PSI and spraying soapy water. :blink:
The following user(s) said Thank You: ScannerDanner
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