Car: 1997 Maxima SE 5spd

Really appreciate any help on this -- already missed deadline for passing smog test!

Backstory: I had to have work on my exhaust done for California smog testing -- previously my car had an aftermarket Y-Pipe (with no precats) and an aftermarket CAT, which caused me to fail both the visual inspection ("tampered" result) and the emissions testing on the smog check.

In order to get the car to pass, a local muffler shop installed a California-compliant aftermarket CAT (rear), and also basically made me a custom Y-Pipe to hold some aftermarket front cats.

After driving around for about 30 minutes wiht the new CAT, I took my car in to be retested. This time I passed the emissions readings with flying colors, but failed visual and functional for two reasons:

1) My Check Engine Light came on during the test. When I took it home and checked the codes, they are 0304, and 0115. Those are the codes for blinking CEL with the ECU (3 long blinks, 4 fast ones, etc) not the P#### codes.

2) My PCV hose was collapsed.

After looking the codes up on here, I found out that 0304 is the Knock SEnsor and 0115 is "Fuel Injection System: Right bank lean"

From previous experience, I believe that the Knock Sensor code (0304) goes off alongside other codes even when the Knock Sensor itself is not the culprit.

0115 is new to me. But from some quick searches on these forums, I've found it often accompanies a bad O2 sensor code or a leak which could be related to this repair? (my O2 Sensors are all about 10,000 miles new). Car is quiet.

Since I had no trouble with my CEL before, I want to believe that these codes after having my exhaust work done are not a coincidence, and I intend to take it back to the muffler shop for them to look at it. Just wanted to post on here though first for some more specific guidance as to what (if anything) I can suspect the correlation is between having work on my CAT and tripping those codes so I can give them some direction or convince them that the events are connected if needed.

Or could the codes possibly be connected to the collapsed PCV hose? (Which I intend to replace valve and hose)

Thanks in advance for any help!

 

The 0115 code (P0171) could be from several causes. Page EC-169 tells us possible causes are:

* Intake air leaks
* Front heated oxygen sensor
* Injectors
* Exhaust gas leaks
* Incorrect fuel pressure
* Lack of fuel
* Mass air flow sensor

Based on what has been done to your car, it could be the O2 sensor was damaged or maybe there is an exhaust gas leak.

Fix the PVC hose and reset the codes. Maybe you'll get lucky, probably not. But you are correct about the knock sensor code. It likes to show up with almost any other code, so fix the 0115 code and probably the knock sensor code will go away.

The right bank is the side of the engine by the radiator. Look and see if the O2 sensor and its wires are OK. The O2 sensor in a stock y-pipe is right by where the y-pipe bolts to the exhaust manifold.

 

Thanks for the reply!

I spoke with the shop now, and told them that it could be related to O2 sensor. They suspect that they may have put my O2 sensor in the configuration for the California model cars with an extra O2 sensor (which my car is not), and said they'd take a look at it and see if they can fix it.