Davis476

Hi everyone,

I believe this subject has been gone over many many times.
I've read almost every post on the subject on this forum and still didn't solve my problem.

I own a 1995 Toyota 4runner V6 with California emissions.

A couple of months ago I turned on the ignition of my car and saw a check engine light. I pulled the code and got a code 21 and 27 indicating the sub heated oxygen sensor is faulty.

Upon testing the sub heated oxygen sensor I noticed that it was faulty and was not working. I proceeded to change to the sensor and that solved the problem momentarily.

After driving for another 40 or 50 miles I got another check engine light on pulling the code I got code 71 indicating a problem with my EGR system.

I followed the troubleshooting and testing as the Toyota manual described I tested the sensor and all resistances were in spec. The EGR valve seems to work perfectly well, when vacuum is applied to it, the engine stumbles.

I suspected the EGR modulator to be at fault. I bought a new modulator and installed it and the check engine light reappears once again.

The VSV is functioning correctly When voltage is applied to it.

Could there be a connection between changing the o2 sensor and the EGR code I'm getting? The 4runner seems to be running fine, but this peaki light is buggin me.

Any help would be appreciated, Im at a loss and don't want to buy new parts if I don't need them.

Much appreciated.

J. Davis

cambob

It could be the EGR itself not opening. They can get gunked up over time. You need to remove the whole valve and check for smooth open/close action. Or maybe the Engine Coolant Temp. Sensor. The FSM shows how to test it. If I remember right you heat up some oil and check it with a multimeter and thermometer. Out of curiosity, what brand of O2 did you use? I've heard that if its non-Denso they can be a problem, but not sure if it would cause what you describe.