# New ECU work at all much less fix the misfire



## Joey-D (Nov 6, 2008)

I have a 2001 Nissan Sentra GXE with the 1.8L Automatic. I purchased this car after it had been sitting for over a year. It fired right up with a new battery and after running for a couple minutes threw 9 codes that include 7 for the o2 sensors on bank 2, one P0303 (misfire #3 cyclinder) and code P1320 (distritutor signal interrupt). I replaced both o2 senors on bank 2, replaced the spark plugs, and switched around the coil on plugs. I believe the 02 sensor codes are becuase of the misfire on #3 cyclinder and therefore a gross strew of the air/fuel ratio. Still a misfire on #3. Took a listening stick and touched to the injectors. #3 was not clicking. There was my misfire. No fuel on injector 3. Ran a can of seafoam through. Replaced all the injectors. Including #3 twice. Checked for spark at plug. That was good. Everything checked out, just no fuel at #3 injector. Cleaned fuel rail. Still nothing. Started the car with the fuel injectors out of the head and visually saw #1, 2 and 4 spray fuel. Just not #3. Without a doubt #3 isn't injecting fuel. Unplugged #4 injector plug and plugged it into #3 injector. #3 injector started injecting, just obviously out of order. So it breaks down to #3 injector is not getting a signal to inject. Check for ground. Good. Checked continuity between the ecm harness and the injector. Good. So then I started the car. Probed the back of the ecm. The wires that went to injectors #1,2 and 4 gave a reading of .450 +/- on the voltmeter. When I probed #3 on the ecm harness it only gave a reading of .100 +/-. That lead me to believe the ecm was bad. I searched high and low for a replacement ecm. Dealership wanted $550, but that would have ate up my profiet on the car. Finally found a yard that had one. Had it shipped. Checked the numbers on it. The top *5ZE1WX* matched. The middle large WX matched. The bottom left JA56Q20 B57 matched. The bottom right didn't match. The difference was 0825 (old) to 0830 (new). So I am almost 100% sure it is the correct ecu. So this morning I fired the sentra up with the old ecu and pulled her in the garage. So I know she runs. Unplugged the old ecu and plugged in the new one. The car wouldn't even fire. I hooked up my OBDII scan tool and it read error on the diagnostic port. Tried erasing codes any way. Still won't start. Tried clearing the ecu using a on off gas pedal way I found on the internet and still nothing. Plug in the old ecu and it fires right up. Just on three cylinders. I am stumped. Any ideas? I don't think its the cam or crank sensor because then it would be random misfires and not just #3. I know for a fact its not injecting fuel at #3 and thats the problem. Thanks ahead of time.


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## sentra2001 (Jan 17, 2010)

I have similar problem. Waht was causing misfire? The ECU?


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## Joey-D (Nov 6, 2008)

The problem was the ecu. The one I had was partially bad and the replacement I got from the salvage yard was really bad. So the third ECU worked. Plugged it in and everything worked perfectly.


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## chimmike (Oct 17, 2002)

good deal. Might want to double check with the dealer and make sure the crank position sensor recall has been done, too.


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