Yesterday, I was fiddling around with the o2 sensor on my 93 DX. I was trying to break it loose, so I could bench test it (just out of curiosity, mostly... it's very old and I want to verify it's working properly). Anyway, it wasn't coming off, so I decided to hit it with some penetrating spray and let it soak overnight. I'm pretty sure I some got on the wires, but I didn't think it was a big deal. So I take the car out this morning and after a few miles, it starts throwing code 43 (Fuel Supply System). Could this be related? Fuel pump primes just fine, main relay has been resoldered, fuel filter is relatively new and injectors have been cleaned somewhat recently.

 

Clean the wires with some brake cleaner.

 

Yea, that didn't seem to help. :/ Time to get out the service manual and multimeter and run the flow chart test. If the o2 sensor decided to give out right after I decided to run a test on it, that would be hilarious.

 

Did you reset the ECU?

 

A hairline crack in the exhaust manifold is common near the o2 sensor and can cause a cel code 43. If you applied a lot of pressure on the o2 sensor when trying to remove it you may have created a hairline crack. Had the crack happen to me in a 93 del sol. Went with a cheap header as a replacement.

 

Yea, Ron. Pulled the 7.5a backup fuse for a few seconds prior to starting it back up

 

Try pulling the fuse for 3 or more minutes.

 

That seemed to do the trick! I left it out for about 5-10 minutes, put it back in, let the car warm up, idled it at 3000 RPM for 2-3 minutes and no more CEL. Ron, with the simple solutions to seemingly complicated problems, once again! :D I thought the prescribed length of time, per the service manual, for removing the backup fuse was 10+ seconds, though?

 

It's rare but the the service manual is wrong sometimes.