First of, don't tell me 'Just get a P08' or 'Just chip it!' or 'Just buy a 4-wire O2 sensor'. I'm not getting a P08, and I'm not chipping it. I've read that there may be a difference in the fuel/timing maps on the P28 versus the P08, with the P08 being more aggressive, but I really don't give a **** as I'm not going to be racing anyone with the stock D15. Also, I'm not looking to spend any more money than I have to, and if all it takes is to clip a transistor to save me $50 for an O2 sensor, then I'm all for it. If any of you would like to donate a 4-wire, you're more than welcome to.

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OK, I know that to convert a P05 to run a 4-wire O2 sensor, all you have to do is add a NPN digital transistor (C144) at Q30.

Now, I'm going to be running a P28 on a D15B in a 90 CRX...I've got the OBD0-OBD1 jumper that has the 4 wires for the O2 sensor, BUT the motor came with a 1-wire, and the CRX isn't wired for a 4-wire...The reason I'm running a P28 is because NOONE had a P08 in stock, and I got a virgin 5spd P28 for a great price from JHP...I'm planning on chipping the P28 this summer when I go turbo, but I am NOT chipping it until then (so don't tell me to just chip it and disable the O2 heater...I already know I can do this, but I'm NOT chipping this ECU yet.)

My question is this...If the only thing required to ADD the heater to the 4-wire O2 sensor is the C144 transistor at Q30, could I just REMOVE the transistor from the P28 and run the 1-wire O2 sensor without any problems? Also, will this affect VTEC engagement?


Thanks in advance...

 

You can't just remove it. The transistor only allows the code on the mcu (stock chip dealy) to function with the heater. It won't work, you just can't do it without chipping it so it doesn't LOOK for the 4 wire. With or without the transistor the stock p28 code will look for a 4 wire. You'll just throw a code. Doubt it will affect VTEC though.

 

You need to install a resistor in place of the o2 heater. The big ceramic style, I think its a 10 watt 10 ohm if I remember correctly. I know it needs to be a 10W you can just measure the resistance.

 

If you want to do this.

You can simply chip the ecu and disable o2 feedback & the o2 heater. You will then require no oxygen sensor at all.

If you have the vehicle tuned properly, you would not need open/closed loop feedback.