My fuel pump has been intermittently not priming in my 1994 stock civic ex over the last few months. Eventually it stopped priming at all. I ended up replacing the QM3 transistor in the ecu. The pump is priming now and everything seems fine except now I have a code 41 (o2 sensor). Let me say I am no soldering pro and am thinking I may have damaged the transistor on install (too much heat).

My question is: is the QM3 transistor involved in checking the o2 before start up ?

I say this because it seems unlikely that the o2 failed while the car sat during ecu repair. So is the o2 actually bad or is the ecu faulting ?

Facts about car:

Main relay engaged before and after ecu repair everytime and still does
All fuses have been tested
No visible capacitor leaks
Car seems to run just fine
Seems like there is an abnormal delay before fuel pump primes but it does prime everytime
I have reset ecu

 

odd situation....