Exhaust Leak, O2 Sensor, and fuel vapor leak

ForrestB · 05-15-2009, 01:44 PM

Long story short, I've had a shop hook my car up to the computer and give me a printout. The mechanics there, as well as those at a number of other shops, including the Ford dealership/garage, couldn't really tell me jack **** besides what came out of the computer.

Three codes;

Code:

P0136 - Heated Oxygen Sensor
P0430/P0442 - Bank #2 Cat. threshold is to low

Now, service engine light (yellow) is on, and I had known about an exhaust leak caused by half-ass welding between exhaust and muffler(s). I had lost an O2 sensor in my old nissan, but replacing was a straightforward job, I just crawled underneath and plugged the new one in.

However, after doing some research online, I came across PaladinMicro, which worked perfect given that I have an 03 GT. Looking up the error codes, this is what I found:

Code:

P0136 - HO2S Sensor Circuit Malfunction (HO2S-12)
Description: The downstream HO2S sensor(s) are continuously checked for maximum and minimum voltages. The test fails when the voltages fail to meet the calibrated limits. Causes include exhaust leaks, faulty wiring and broken/contaminated O2 sensors.

This was not surprising or worrying to me, as broken O2 sensors aren't really a big deal, besides the fact that it might just be the exhaust leak causing it.

Code:

P0430 - Catalyst System Efficiency Below Threshold
Description: Indicates Bank 2 catalyst system efficiency is below the acceptable threshold. A wide range of causes, but many related to O2 and exhaust.

Again not all that troublesome, it seems to pertain to the O2 sensor or exhaust leak, probably not a big deal.

Finally however,

Code:

P0442 - EVAP Control System Leak Detected
Description: The PCM monitors the complete EVAP Control System for presence of a small fuel vapor leak. The system failure occurs when a fuel vapor leak from an opening as small as 1.016mm (0.04 in) is detected by the EVAP running loss monitor test.

This code scares me. It could just be lack of knowledge and experience with cars, but I have no idea what the EVAP system handles, don't like the sound of a fuel vapor leak, and none of the listed causes on the site seem to relate to a malfunctioning O2 sensor or an exhaust leak. I'd like to believe that because the P0442 code was paired with the P0430 one, and the description on the printout made no mention of EVAP CS leaks, the codes are just always paired together and there isn't necessarily a fuel vapor leak.

But I'm pretty new to this kind of thing. I'd appreciate any advice or insight into these problems. Money is tight for me right now, and I can't really go to my parents for cash either. The garage that did the original exhaust (and who's faulty welding caused the leak) is going to seal it up for free; that's going to be the first thing I take care of. After that, if I've still got problems, I'll have the downstream/Bank2 sensor replaced, but Ford gave me a price of 120. I've been advised to buy from Ford and not a third party when it comes to O2 sensors, but that's pretty steep for such a basic part.

Anyways...advice?

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ForrestB · 05-17-2009, 11:03 PM

Awesome...

Anyways, I got the exhaust leak fixed, CE light is still on. Next paycheck I'll hopefully be able to afford a sensor. Still worried about the other error codes.

cliffyk · 05-18-2009, 04:48 AM

My web page also list possible causes for these codes, have you gone through the lists and checked what you can?

The EVAP code could be something as simple as a loose gas cap.

The P0136 (HO2S #12) and P0430 (Bank 2 Cat) are obviously for different banks, how many miles on your car?

If not a wiring problem then the bank 1 (passenger side) rear sensor has failed. I won't get into the Bosch vs. Ford issue except to say the I have used the Bosch replacements from my FLAPS ($70 or so now) on several cars with none of the problems attributed to them by many.

The cat efficiency thing may be a bad cat on the driver's side, or the rear O2 sensor failing but not yet dead.

One last comment, snide remarks like "Awesome..." made because no one responded to you posting in the time frame you thought appropriate will not make it anymore likely that someone Will respond. I understand your frustration, however it was the weekend and many people have things to do other than browsing the forums.

ForrestB · 05-20-2009, 01:19 AM

Definitely appreciate the insight. I'll have to do some more research and try and talk to some people with the same model/year car as me...to be honest I'd rather be safe than sorry, even if it means shelling out the extra cash.

I broke 60000 miles last week.

And about the remark, I mean, I am obviously a noobie around here, but I'm pretty experienced as far as forums go. I know it didn't do me any good, and maybe even swayed people against posting; my goal was to express disappointment. I certainly don't want to make a bad first impression around here, but at the same time this is one of many resources I can use on the internet and in my locality...

At the same time, bumping the thread was about the best I could do. And I'm not sure what you mean about the weekend, in my experience, people spend more time surfing the web and browsing forums on off days, but I suppose there's not much to be gained from debating that.

Anyhow, thanks again for the insight. I welcome any more. I'm trying to pick up a second job in a garage now that school is winding down, which will both give me a lot of extra money and some more practical experience with cars. Hopefully I can get this sorted out quickly. As simple as they are, O2 sensors really affect the way a car drives, and I'd sure like to get mine back to driving like it should.