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Code P0102 ODB2 permanent code but no dash lights and runs great?

Tiny
JOXER
  • MEMBER
  • 2021 TOYOTA 4RUNNER
  • 4.0L
  • V6
  • 4WD
  • AUTOMATIC
  • 12,900 MILES
Hello, I recently purchased an Innova 6100P ODB2 reader and decided to try it out on my vehicle listed above. To my surprise it gave me a P0102 permanent code. Odd since it only has 12,900 miles, no dash lights, engine runs great city and highway. Can get 18.5 MPG freeway. Idles fine. All the monitors show green with a “completed” status on my ODB2 scanner. I watched a few YouTube videos and most of the fixit suggestions were to clean the MAF. I bought MAF spray cleaner and cleaned the MAF as instructed. Let it dry thoroughly. The permanent code will not go away. I’ve seen videos about performing a “drive cycle” to get rid of the code however, it’s confusing on which drive cycle I should perform. I don’t need to smog my 4Runner for several more years, but this code really bugs me. I’m not sure if there’s something really wrong or not. I “baby” my 4Runner and it has low mileage as I am retired and don’t drive that much. I’m in California. I’m leaning towards running a drive cycle but which one and why if my monitors are all green? Thanks in advance!
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Thursday, October 26th, 2023 AT 7:32 PM

10 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Hi,

If the monitors are all reset, there isn't a drive cycle that is needed. When there is an incomplete monitor, that is when you need to drive it.

Because this vehicle is new, it needs to be checked at the dealership. The code you have indicates a low voltage issue from the MAF. When this DTC is set, the ECM enters fail-safe mode. During fail-safe mode, the ignition timing is calculated by the ECM according to the engine speed and throttle valve position. The ECM continues operating in fail-safe mode until a pass condition is detected. I believe that is where you are getting the drive cycle info. Keep in mind, when the ECM continues in a fail-safe mode, it will run fine. However, it isn't running as efficiently as it should. Make sure this is resolved before the warranty has expired.

As far as a permanent code, in this case, the code is set when there are two consecutive drive cycles when the problem is present. If you disconnect the battery (neg first) then the positive, tie the two cables together with a zip tie, and allow it to remain that way for approximately 15 minutes, it should clear the code. However, if the problem is still present, the same thing will happen after the second trip

See pics below Note: Pic 1 describes the code, pic 2 shows the most common repairs (yours is too new for an air filter but there could be a wiring or sensor-related issue) and pic 3 explains how it is set and how you can try to clear it.

Let me know if this helps.

Joe

See pics below.
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Thursday, October 26th, 2023 AT 8:27 PM
Tiny
JOXER
  • MEMBER
  • 3 POSTS
Thanks for the explanation and pics Jacob and Nickolas! I will certainly head to the dealer and get it checked out.
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Thursday, October 26th, 2023 AT 9:52 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Hi,

You are very welcome. If you have a chance, let me know how things turn out.

Take care,

Joe
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Friday, October 27th, 2023 AT 12:47 PM
Tiny
STEVE WALKER
  • MEMBER
  • 11 POSTS
There is nothing wrong with the car with only a permanent code in place. A dealer would not be able to fix anything but still would charge the customer.
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Monday, October 30th, 2023 AT 3:18 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Hi,

Thanks for the info, Steve. There isn't anything wrong with the vehicle. You are correct. However, it is still under 100% warranty and this shouldn't be set. A dealership may need to flash the PCM or other module for the code to be deleted. Note that the manual indicated the battery to be disconnected to clear it. If that doesn't work, there is a problem at some point that needs to be identified and repaired for the light to stay off. Since this is such a new vehicle, it is recommended to return to a dealer to record the concern and hopefully find a manufacturer resolution that hasn't been shared yet.

Joe
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Monday, October 30th, 2023 AT 7:06 PM
Tiny
JOXER
  • MEMBER
  • 3 POSTS
Thanks Joe and Steve. I decided to disconnect both battery terminals and wait 15 minutes before reconnecting them. Now I have 7 incomplete monitors. The P0102 is still there however, now I can perform a Toyota specific drive cycle. I’ll do it this coming Sunday so as not to hit too much traffic. There are no dash warning lights and my truck drives the same with no issues. I’ll give you an update after. Thanks again!
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Monday, October 30th, 2023 AT 8:35 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,643 POSTS
The code P0102 on a 2021 Toyota 4Runner indicates a problem with the Mass or Volume Air Flow (MAF) Circuit. At this point cleaning it will not help, you must replace it.
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Tuesday, October 31st, 2023 AT 9:29 AM
Tiny
STEVE WALKER
  • MEMBER
  • 11 POSTS
Joe,

A permanent code does not indicate there is anything wrong with the vehicle. The dealer would not be able to do anything with it besides charge for a diagnosis. The permanent code is working exactly as it should be and will clear when the ECU is satisfied the problem is corrected.

Ken,

It's only a permanent code present not a current or active code, no check engine light. There is nothing to repair. Stop telling people to replace perfectly good parts.

If I had to guess sometime in the cars past someone started it up with the MAF unplugged, got a Check Engine light, cleared it and not a permanent code is waiting to clear.
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Tuesday, October 31st, 2023 AT 11:47 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
I agree, Steve, but the vehicle is under warranty. If the code doesn't turn off (and it hasn't), it should be a warranty issue and they need to be aware it is present. That is why I made my recommendations. If my 2021 4runner had a permanent code and the vehicle had under 13K miles, I assure you a dealer would see it and I wouldn't pay a cent. LOL Those are my thoughts as far as documenting potential issues. Plus, he has been driving the vehicle, so if the problem has been resolved, the code should be gone. Note that the CEL was never turned on, but the permanent code is still present.

However, all in all, you are correct when you indicate it is working as designed. I totally agree. If there wasn't a problem, it should have reset. Actually, if there wasn't a problem, it never should have set. And based on the idea of how well it has been taken care of, I doubt anyone was under the hood disconnecting things.
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Tuesday, October 31st, 2023 AT 9:14 PM
Tiny
STEVE WALKER
  • MEMBER
  • 11 POSTS
On many cars you have to unplug the MAF to even check the air filter. So, while the owner may not have seen the check engine light there is a good chance it was on for at one time for some reason. Or course it had to have a confirmed code at one time because it has a permanent code present. A permanent does not show up unless you have a confirmed code. So, the permanent code is just a copy cat code so to speak.
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Tuesday, October 31st, 2023 AT 9:45 PM

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