View Full Version : MIL Eliminators, O-2 Sensors, Change All Four?

05-17-2005, 10:57 PM

I have a persistant problem while incorporating MIL Eliminators and attempting to get the computer to reset.

Setup: I have a '96 Cobra that came with a custom-fitted (from a different year of Mustang) Borla Cat-Back with Basanni X-pipe. Not surprisingly, the "Check Engine" light (MIL) was on constantly before I attempted the MIL Eliminator installation. The Cobra also came with a SuperChip, though I have none of the literature that originally came with the chip. I also replaced the front two (pre-catalytic convertor) O-2 sensors, shortly after installation of the MIL eliminators. I also disconnected the negative battery terminal to reset the computer after I replaced these O-2 sensors.

Immediately after I reset the computer by disconnecting the negative battery cable, the "Check Engine" light went out but only for about twenty minutes/fifteen miles. I then tried re-seating the connections to both the front two O-2 sensors that I replaced and the MIL Eliminators. However, the problem continues: I can reset the computer by disconnecting the battery cable, but the "Check Engine" light comes back on after about 10-15 minutes/10-20 miles.

After reading a few threads on the Forum regarding exhaust mods and MIL Eliminators, I took "Lorena" to Auto Zone to get an error code check on her computer. The error codes are as follows:

Error 1: P1443: "Manufacturer-Controlled Auxilliary Emission Control Malfunction"

Error 2: P0516: "O-2 Sensor Circuit Malfunction: Bank 2, Sensor 2"

Error 3: P0161: "Sensor Heater Circuit Malfunction: Bank 2, Sensor 2"

During re-seating of the connectors, I noticed that the Borla came with four O-2 sensors installed in proximity to where catalytic convertors would have originally resided. I presume that the computer uses a sum-and-difference check between identical (Bosch Part #13127) pre-catalytic convertor and post-catalytic convertor O-2 sensors, and that the MIL Eliminator "tricks" the computer into thinking that the catalytic convertors are still present and working.

All that aside, given the error codes above, should I replace the back two (post-catalytic convertor) O-2 sensors and see if the computer re-calibrates within range, or is there something else that I need to do? (The sensor heater circuit error leads me to believe that one of the back two O-2 sensors is bad, but I could easily be wrong, as I'm no mechanic and am also fairly new to the world of Cobra.)

Thanks for your help.
--Professor Chaos

05-18-2005, 08:09 AM
Which eliminators are you using, I have the BBK. Coming home from the Buckeye meet my Check engine light came on. Code was low catylis. Cleared it with a hand held reader at Instant oil change. Hasn't come back on yet. But I might have 10 miles since. So it may come back hope not.
On yours if there's two sets behind where the cats used to be try the other set.

05-18-2005, 08:40 PM
The first set of o2 sensors helps control the fuel air mixture and the 2nd set reads the exhaust and that is where the mil eliminators go they slow down the signal to correct it for the computer. I would change the rear set and try resetting the computer. I would also make sure you still have power to the 02 sensors.

05-20-2005, 11:11 PM
Which eliminators are you using, I have the BBK. .

I bought them at Mustangs Unlimited in Lawrenceville, GA:
Mustangs Unlimited MIL Eliminators (http://www.mustangsunlimited.com/itemdy01.asp?T1=MIL02+01&Category=&catkey=74-01)

The MIL Elimintors sold at Mustangs Unlimited are as affordable as they are anywhere else I've seen them online, and they feature the "plug-and-play" connectors. Thus, there's no threat of messy wiring jobs and no threat of the other connection-related/oxidation-related problems that might be associated with the "wire-it-yourself" jobbies. :)

--Professor Chaos

05-20-2005, 11:22 PM
The third error code is actually "O-2 Sensor Heater Circuit Malfunction: Bank 2, Sensor 2". My guess it that the sequence of three codes--all O-2 sensor-/emissions control-related--pretty much narrows the problem to one of the two post-catalytic-convertor O-2 sensors.

When my check clears next week, I'll replace both of the back O-2 sensors and reset the computer. If that doesn't work, I'll sit down and cry. ;)

--Professor Chaos

06-08-2005, 08:44 AM
Replacing the back two O-2 sensors indeed resolved the issue.

Thanks for your input.

--Professor Chaos

06-09-2005, 01:50 PM
Good to hear that resolved your issue.