Hard reboot for ECU needed possibly?

Tiny
JESSS
  • MEMBER
  • 1998 NISSAN ALTIMA
  • 2.4L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 120,000 MILES
Installed used engine, changed spark plugs, wires, dist cap, rotor, air filter, fuel filter, Mass Airflow Sensor, EGR, O2 Sensor

No vacuum leaks.

Check engine light still comes on intermittently reading lean bank one.

Is there a hard reset for the ECU I should perform specific to my car to stop this so I can pass smog?
Monday, January 19th, 2026 AT 4:52 PM

9 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 55,046 POSTS
Yep, you can try a hard reboot, here is a video to show you how.

https://www.youtube.com/watch?v=INiDRO5A5MY

Is there any intake or exhaust leaks, these both can cause a lean mixture, here is a guide to help.

https://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers

This video will show you how to check for vacuum leaks.

https://www.youtube.com/watch?v=LRKWV4Are5c&pp=0gcJCYcKAYcqIYzv

Please upload a short video with the engine running in your response, so I can see what's going on. Please go over these guides and get back to us.

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Tuesday, January 20th, 2026 AT 9:44 AM
Tiny
JESSS
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Thank you for your help. I go to my mechanic tomorrow. They checked already and said there are no vacuum leaks. I will let the look at it again and when I pick it up after they clear the codes again I will drive it like the manual says when it's new so the ECU learns correctly because I put a used like engine in it.
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Tuesday, January 20th, 2026 AT 6:37 PM
Tiny
KEN L
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An exhaust leak will cause this as well. When you say I replaced the fuel filter, was it the fuel filter inside the gas tank?
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Wednesday, January 21st, 2026 AT 9:03 AM
Tiny
JESSS
  • MEMBER
  • 6 POSTS
Hi,
No it was the external fuel filter that is under the hood.

Also, I watched your video and bought the little wire with alligator teeth. They sold me a set that has two separate wires one red, one black with teeth. Can I use one of those to attach to the positive and negative to drain the car like you did?
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Wednesday, January 21st, 2026 AT 11:48 AM
Tiny
JESSS
  • MEMBER
  • 6 POSTS
Mechanic is not available until tomorrow so I want to try to drain and then relearn my ICU to my cars specific pattern in the manual like you said.
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Wednesday, January 21st, 2026 AT 11:53 AM
Tiny
JESSS
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  • 6 POSTS
Do you think I should wait to do that until after the mechanic has it for a day to see if they can find any exhaust leaks or anything else.
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Wednesday, January 21st, 2026 AT 11:55 AM
Tiny
KEN L
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  • 55,046 POSTS
Yes, I would wait until the mechanic looks at it.
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Friday, January 23rd, 2026 AT 8:41 AM
Tiny
JESSS
  • MEMBER
  • 6 POSTS
Hi Ken,
Do you have a phone number I can call you at? I really need your expert opinion. I just picked my car up from the mechanic and wanted to go over what he thinks. My number is 805-276-6834
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Wednesday, January 28th, 2026 AT 12:03 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 55,046 POSTS
We cant make calls, can you explain here what is going on?
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Thursday, January 29th, 2026 AT 8:53 AM

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