97 NISSAN Sentra ECU reset SES code erase

nissan
sentra

#1

My 1997 Nissan Sentra SES (service engine soon) yellow light came on. Local auto stores wont erase the code due to EPA restrictions but they told me the error codes are P0440, P0446.
Auto forums recommended removing rust around the gas cap and get a new gas cap. I removed all the rust, got a new gas cap, but the SES light never went away on its own. People are saying that I have to disconnect the battery to erase the code. I did that, I left the negative batt terminal unscrewed over night, touched the unplugged negative wire with the positive wire for a few seconds to drain all capacitor charges, but the error code is still there, SES light remains lit.
Read in another forum how to Reset ECU in cabin without battery disconnect. Below is the method:------>

  1. Put the car in “ON” mode, do not START.
  2. AT the third second (3 dings) after turning to “ON” (again NOT started) position, Floor (all the way down) and release the accelerator pedal fully 5 times in less than 5 seconds.
  3. With the gas pedal at release position, wait about 7 seconds, then floor the accelerator pedal and hold for 10+ seconds. Hold pedal down until the SES Check Engine Light will start to blink slowly. (MY SES LIGHT NEVER BLINKS).
  4. Release the pedal and floor it down once again and hold for 10 seconds. After these 10 seconds the check engine light will begin to flash much more rapidly (MY SES LIGHT NEVER BLINKS). Release the pedal after 15 seconds or done flashing rapidly. Turn the car off wait for a few seconds and then back on. The ECU/ECM is now reset. <-----

Neither methods worked for me. For the second method, MY SES LIGHT NEVER BLINKED. What am I doing wrong? How can I clear the code from the memory?


#2

You probably still have a problem with the evap system. A gas cap is a common cause for the code but not the only one. You can buy an inexpensive code reader from Walmart, auto stores etc. that will clear the code. But even after it is cleared I bet it will come back.


#3

You have a large EVAP system leak, and there’s a problem with the EVAP system vent valve circuit.

If the vent valve doesn’t close when the EVAP system performs its self-test, It’s going to detect a large leak, and that’s why the SES light doesn’t turn off.

You haven’t fixed the problem.

Tester


#4

It seems like OP should be able to clear the code with a proper computer reset. It’s just that the CEL will likely come back on again next time it tests the evap system. I don’t know how to turn the CEL on your make model. Disconnecting the battery works on my Corolla. But if there’s a problem b/c of something like a disconnected connector, it will come back on again once I reconnect the battery and start the engine.

As posted above, the engine computer every once in a while tests the airspace in the top part of the tank to make sure it is air-tight. To do that test all the various valves involved must close properly, then the pressure sensed will verify it is air-tight. So you got a problem with one or more of the pertinent valves, or the pressure sensor isn’t working.

A mechanic with a Nissan scan tool should be able to turn off the CEL at least temporarily. Why the gas pedal method doesn’t work, one idea is the throttle position sensor isn’t working properly. BTW, if emissions testing is the reason you want to clear the code and turn the CEL off, what you are doing won’t work. The emissions testing computer can tell that you’ve done that, and that will result in an immediate failure.


#5

Any mechanic can, but I doubt if any mechanic will. Not only does he know that the car doesn’t meet emissions requirements, he knows he’s probably going to have an angry customer in his waiting room in another day or two complaining that he didn’t fix the vehicle.

Also, depending on the regulations in his state, he may be risking the loss of his certification to do state emissions testing.


#6

This is an ongoing thing for me. The rust around the gas cap comes back every year and I have to scrape it off. I need a way to be able to do this every year when the SES light comes back during the rainy season. The “In-cabin pressing accelerator pedal method” worked for me a few years ago. I can no longer remember the timing sequence for pressing the pedal. None of the youtube videos are for my model. If you have done this for my car model and cleared the SES light, please let me know the pedal pressing sequence.
BTW, where is the fuse / circuit breaker located for the ECU/ECM unit in 97 Nissan Sentra?


#7

This won’t go away until you fix it.

446 indicates that the vent valve circuit is flawed. It’s normally open, solenoid off, and it closes(solenoid on) to test the system for leaks(which might only happen once every 500 miles). A lot of times you’ll find the solenoid cracked open and the vent is caked with dirt. A clogged vent will also cause the refueling pump to kick off repeatedly because the flow back-logs due to not being able to vent.


#8

The SES comes on even when the gas cap is loose and returns code P0446 and p0440. It happened even when the car was brand new.