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Discussion Starter #1
I replaced all of my O2 sensors, upstream and downstream.

When I started my car it turned over but after about 5 seconds it begins to flutter and slowly turn off. Also, if I press the accelerator the engine flutters and starts to rumble a bit.

I tried resetting the ECU to no avail. I did the pedal dance and I also disconnected the negative batt terminal and connected it to the positive for 15 min but neither worked.

I am getting a P0603 and P0300 codes from my reader. Those relate to the ECU but after resetting it I am thinking I may need to get a new ECU set at factory settings.

Anyone else have this problem or know of what I am missing?
 

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I replaced all of my O2 sensors, upstream and downstream.

When I started my car it turned over but after about 5 seconds it begins to flutter and slowly turn off. Also, if I press the accelerator the engine flutters and starts to rumble a bit.

I tried resetting the ECU to no avail. I did the pedal dance and I also disconnected the negative batt terminal and connected it to the positive for 15 min but neither worked.

I am getting a P0603 and P0300 codes from my reader. Those relate to the ECU but after resetting it I am thinking I may need to get a new ECU set at factory settings.

Anyone else have this problem or know of what I am missing?
Did you replace the O2 sensors because of this issue or did this issue only start happening after you replaced the sensors? If the latter, I'd suggest going back over everything you touched while replacing the sensors and make sure you didn't inadvertently leave anything disconnected (or damaged a wire/connector).

The procedure for diagnosing that code before writing off the ECM is to check the 15A fuse for the ECM in the fuse box and make sure you're getting battery voltage at Terminal 121 of the ECM connector. I'd also check all the ECM grounds (including sensor grounds). This information can be found in the "Engine Control System" file of the service manual for your car at the Nicoclub website: https://www.nicoclub.com/nissan-service-manuals

Good luck and let us know if you find exactly what the problem is.
 

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Discussion Starter #3
Did you replace the O2 sensors because of this issue or did this issue only start happening after you replaced the sensors? If the latter, I'd suggest going back over everything you touched while replacing the sensors and make sure you didn't inadvertently leave anything disconnected (or damaged a wire/connector).

The procedure for diagnosing that code before writing off the ECM is to check the 15A fuse for the ECM in the fuse box and make sure you're getting battery voltage at Terminal 121 of the ECM connector. I'd also check all the ECM grounds (including sensor grounds). This information can be found in the "Engine Control System" file of the service manual for your car at the Nicoclub website: https://www.nicoclub.com/nissan-service-manuals

Good luck and let us know if you find exactly what the problem is.

This started AFTER I replaced them. My step is to go back through to see if I missed something or possibly something else broke or tore.

I will definitely check the wiring and see the fuse is good to go and let you know. Thanks for the quick response
 

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I retraced all my steps. Reconnected all the harnesses to the sensors. When I moved my manifold there was a vacuum hose to the rear of it that was hanging. My guess is I didn't place the fastener clip secure enough the first time and it probably slid off when I put the manifold back. I tightened the fastener and put it all back together and it runs like normal. No more codes. Thanks for help!
 

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I retraced all my steps. Reconnected all the harnesses to the sensors. When I moved my manifold there was a vacuum hose to the rear of it that was hanging. My guess is I didn't place the fastener clip secure enough the first time and it probably slid off when I put the manifold back. I tightened the fastener and put it all back together and it runs like normal. No more codes. Thanks for help!
Good to hear you didn't need a new ECM! It's interesting that a loose vacuum hose set the P0603 although the P0300 isn't surprising--which hose came loose, the brake booster or PCV? Perhaps the ECM code was thrown as the car was stalling due to voltage fluctuations to the ECM.
 
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