1G ECU problem? O2 > 1v

[Mits3gts]

I just installed my EPROM ECU with a custom chip from DSMchips.com. The car runs so much better, idles perfect and everything.

One thing that concerns me is when I first start the car or just turn the key to the 'on' position the o2 voltage on my logger and my digital o2 gauge will read almost 3 volts and will slowly drop down to .20 and then start cycling normal (when the car is running of course). My fuel trims are perfect, just curious as to why the voltage will read almost 3 volts.

This only happened when I put this ECU in. Any ideas?

 

[steve]

Assuming what you're seeing on that digital gauge is actually present on the ECU pin, I've seen this happen when the capacitor arrays used for EMI filtering go bad and charge up from the voltage on one of the pins next to the O2 sensor line.

Steve

 

[Mits3gts]

can this cause any major damage? i just had the the ecu socketed and the caps replaced. everything looked all good and clean,i have no problem checking the ecu again,but where should i look? i noticed today when i turned the key,the o2 meter was at 6 volts!! thanks alot for the help

 

[steve]

I have no idea how the O2 sensor reacts to having a voltage applied to it but I don't think it's a very good thing. If I did the work to the ECU send it in and I'll take care of it.

Your not going to see anything by looking at the ECU. The part in question is under the metal heatsink and unless it's catastrophically failed you wouldn't see anything abnormal. It's not apparent until you remove the part and measure each capacitor in the array for capacitance and check for leakage between them. It took me a while to figure out what was wrong the first time I saw a ECU with >1v on the O2 line.

Steve