Hey all. I just bought my car maybe 1 month ago. First mod was a 3" straight x-pipe catless exhaust. (sounds killer!) But, as expected, the CEL light turned on after a few miles. I assumed it was a cat inefficiency code and was already set on getting an EPL flash to add power and also address this code so i did. I shipped the ECU out to them and had them bench flash it.

I got the flash just today and the CEL was still there so i took my handy dandy scan tool and came up with a P0156. Supposedly a "Oxygen Sensor After Catalytic Convertor (Cylinders 4-6) Intercore short circut.

To make this simple.. How do i fix this ? I'm new to this platform so any help would be greatly appreciated !

 

is bank 2 the drivers side or passenger ?

 

Bank 2 is the passenger side.

 

A cut/paste from a thread:

https://www.6speedonline.com/forums/...elp-996tt.html

here on this P0156 error code subject a while back:

P0156 - O2 sensor after TWC, Bank 2 -- signal implausible.

Possible fault cause:
Short circuit to ground in signal wire.
Intercore short circuit.

The above error code has some tests to run to determine if the problem is with the sensor, its connector, the wiring harness, or the DME.

Since the error code appeared shortly after you installed some exhaust mod's I suspect there is an exhaust leak. I'd eliminate that before messing with the sensor.

Also, if you removed the turbo from its exhaust manifold there is a metal o-ring that I believe goes between the turbo and the exhaust manifold. Whenever the tech removes the turbos in my car he always replaces these metal o-rings.

 

call Tony

 

There's no exhaust Leak and I am waiting to hear back from Tony.

In the mean time i went to the dealer 2 days ago and they noted that the J bungs on my exhaust route the wire in an awkward manner as they touch the engine block and also make an aggressive u turn at some point. I've attached a picture. They suggested to get rid of the J bung and have the o2 sensor go directly straight into the piping. The wire may have been shorted due to this scenario, being stretched and close to direct heat.
I've ordered the Bosch post cat sensor and will probably have the bungs re-positioned so that the wires are not in any awkward positions and away from heat. They also suggested mounting the wiring in the "clipping points".

Any thoughts ? Seems legitimate to me.

 

Since 2 of the possible causes of the P0156 have "short circuit" in them definitely check the wiring.

I've been at the O2 sensors on my Boxster just a couple of times -- the Turbo never (had them replaced when they needed it) -- and the wiring routing is very well done. When I installed new sensors I made sure to duplicate the routing.

The positioning of the sensors I can't really advise you other than in general terms. I know the sensors want to be in exhaust flow from the converters. This keeps the sensor hot and lets it get a good sampling of the exhaust gases so it can measure oxygen content.

 

Good point about the sensors being in the exhaust flow. I have an appointment saturday with the shop that did the exhaust. Im going to get rid of the "J" bung extenders. EPL did advise that the secondary o2's help control fueling so it may be wise on my part to have them directly into the pipe rather than spaced.

This may help the car run better as well as gas mileage has been horrible after the flash and it just doesn't seem to run smoother, more powerful etc.. as i've been reading the stellar reviews on other EPL users.

 

Secondary O2 are generally used to check catalytic performance and not effect fueling as its post catalytic converter and won't show true A/F. Those bent bungs may have been an attempt to fool the sensors by taking them out of the flow path. If you've got space and no catalytics I'd remove them and let the tune handle the lack of converter. A short seems pretty probable...