350Z Check Engine Light With High-Flow Cats?

By: Anonymous

Basically, this is a solution to the dreaded CEL that many of us get from switching to testpipes. The idea is to place a gap between the pipe and the sensor to reduce the amount of exhaust gases that the sensor will see/detect. This is becoming a very popular mod over since it is NON-PERMANENT, and it does not require modification to the O2 sensor harness. Normally, I would throw a CEL about every 85 miles, so far this mod has been worthwhile.

Parts/tools Required:

1) Help! Part # 42002 and/or 42009 by Motormite, these are known as sparkplug-arresters, which should be available at any generic auto supply store (e.g. Pepboys, Autozone, etc.). Should run about $5 per package.

2) Tools
– means to lift/secure vehicle
– 10 mm socket or wrench
– 7/8” wrench for O2 sensor (or 22 mm)
– drill and 1/2” drill bit (read below)
– Dremel tool and various bits
– zip ties & dykes

Procedure:

1) Jack up car and secure with jack stands.

2) Remove 2 plastic nuts and shield covering the O2 sensor/harness junction (10mm), this will make the R&R of the rear O2 much easier.

3) Remove the rear O2 sensor, which is the one downstream of the cat.

4) Modify the sparkplug-arrester(s).First I drilled out the arrester using the 1/2” drill bit, then I used various drill bits and the Dremel to shave the rest until the sensor would fit. If you have the means to measure the sensor and get the appropriate drill bit, that would be highly recommended.

5) Install arrester(s) into downpipe & replace O2 sensor.

There are several combinations for the fix. The 42002 is a tapered-mount and the 42009 is a flat-mount with a crush washer. The 42002 (tapered) is notably longer in length than the 42009 (flat).

I elected to start off with the 42002 (tapered) only, which is the longer of the two, this worked out fine for 120 miles. Next, I placed a non-drilled 42009 (flat) in front of the 42002, so far no problems.

6) Replace 2 plastic nuts and shield covering the O2 sensor/harness junction.
7) Secure harnesses with zip ties.
8) Clear DTC’s/Reset ECU.