2007 XC70
223k miles
Recently started getting these codes, clear them and they come back within about a week:
ECM-400C Three-way catalytic converter (TWC) efficiency, bank 1 - Signal too high
ECM-430C Fuel tank system, leakage - Fuel tank cap missing
ECM-439C Fuel tank system, leakage - Major leak
Swapped gas caps with another P2, codes stay with the car do not travel with the cap.
Replaced leak detection pump 30774518 but alas no change to codes.
The EVAP codes may be different issue than the cat code, but right now I'm chasing the cat code. If I can fix the cat code and the others are still here, I'll probably smoke test it.
STFT and LTFT look great, no evidence of vacuum leaks there.
Front and rear O2 sensor graphs look EXACTLY like this guy's viewtopic.php?t=95764 i.e. the front looks good (flat) but the rear does not, it slowly oscillates between about 0.5 and 0.9. Apparently his issue was the cat.
Catalytic converter does not rattle when banged on, FWIW.
To help determine if the issue may be an exhaust leak and not a dying cat, I looked for exhaust leaks by hooking up my shop-vac output to the tail pipe, and spraying along the exhaust (especially up front from the engine to the back of the cat) with soapy water. I found only one leak, between the turbo flange and the down pipe.
The bubbling was more dramatic with the shop-vac and cold metal but here's what it looks like if I spray soapy water on the junction at idle, before the flange gets too hot:
- exhaust leak at down pipe junction
2. Any tips for this job?
3. I see a lot of advice to replace the hardware but is it really necessary in this case? In the pic those bolts look pretty clean. It looks like this car has bolts there not studs/nuts.
4. Other than smoke testing, and advice on what else to check for this set of codes?
