2020 4runner limited 35K

engine has no symptoms.

hooked obd2 scanner and got code P1605 "Rough idling"

Should I ignore, reset codes and see if it comes back.

any idea what it could be?

bump...

did you google it? looks like its either a leak in the air intake system or a few sensors could be faulty. reset and see what happens. is it running smoothly?
Air Leak in Intake System
Faulty Mass Air Flow (MAF) sensor
Faulty Engine Coolant Temperature Sensor
Faulty Fuel Pump
Faulty Throttle Body Assembly
Faulty Engine Control Module (ECM)

I'm sure I posted an answer last night, but it seems to have disappeared.

That code is not "rough idling" but rather a knock control malfunction for Toyota: P1605 DTC According to that link, it is an ECM problem.

It never hurts to reset the code and see if it comes back. If it comes back, however, you will need to get a professional evaluation.

Do you have a good scan tool that you can read stored freeze frame and real time data? If not, and no other symptoms, clear it and see if anything else develops. Worth doing a visual inspection and look for any chewed wires or signs of rodents, especially in the V around the injectors, and the wiring to the coils.

Here is just the intro section on that DTC, followed by like 40 pages of flow charts with links to other sections. See part I bolded below

P1605
This DTC is stored if the engine speed drops below the set speed.
Using the Techstream, the conditions present when the DTC was stored can be confirmed by referring to the freeze frame data. Freeze frame data records engine conditions when a malfunction occurs. This information can be useful when troubleshooting.
It is necessary to check if the vehicle ran out of fuel before performing troubleshooting, as this DTC is also stored when idling is unstable due to running out of fuel.
DTC NO. DTC DETECTION CONDITION TROUBLE AREA
P1605 After 5 seconds or more elapse after starting the engine, with the engine running, the engine speed drops to 400 rpm or less (1 trip detection logic). • Air leak in intake system
• Purge VSV
• Mass air flow meter
• Engine coolant temperature sensor
• Wire harness or connector
• Air fuel ratio sensor
• Power supply circuit (purge VSV, fuel injector assembly, ignition coil assembly)
• Fuel pump
• Fuel pump control system
• Fuel line
• Throttle body with motor assembly
• Camshaft timing oil control valve assembly
• Knock sensor
• Ignition coil assembly
• Fuel injector assembly
• Spark plug(s)
• Air conditioning system
• Power steering system
• Electrical load signal system
• A/T system
• Park/neutral position switch assembly
• ECM
INSPECTION PROCEDURE
HINT: In contrast to normal malfunction diagnosis for components, circuits and systems, DTCs P1603 and P1605 are used to determine the malfunctioning area from the problem symptoms and freeze frame data when the user mentions problems such as engine stall.
As these DTCs can be stored as a result of certain user actions, even if these DTCs are output, if the customer makes no mention of problems, clear these DTCs without performing any troubleshooting and return the vehicle to the customer.
• If any other DTCs are output, perform troubleshooting for those DTCs first.
• Use any information from the customer problem analysis about the condition of the vehicle at the time when the problem occurred (how the engine stopped, conditions when the engine was restarted, etc.) as a reference.
SYMPTOM SUSPECTED AREA
Engine vibration occurs and engine stops Air-fuel ratio abnormal
Engine stops with no engine vibration Ignition system, injection stoppage, high load from external parts
Engine can be started with accelerator pedal depressed Insufficient air volume
Rough idling after engine started Air-fuel ratio abnormal, abnormal combustion
• Read freeze frame data using the Techstream. Freeze frame data records engine conditions when a malfunction occurs. This information can be useful when troubleshooting.
• When confirming the freeze frame data, be sure to check all 5 sets of freeze frame data .
• When DTC P1603 (Engine Stall History) is stored, DTC P1605 (Rough Idling) is also stored. When confirming freeze frame data, check DTC P1605. The ECM stores DTC P1605 first. Therefore, 5 sets of freeze frame data can be confirmed through DTC P1605, enabling the technician to obtain more information.
• When confirming freeze frame data, if there are multiple items related to the cause of the malfunction, perform troubleshooting for all related items.
• Try to operate the vehicle under the conditions recorded in the freeze frame data which were present when the malfunction occurred. Confirm the data at this time and the data when the engine is idling (engine warmed up, no load, and shift lever in D or N) and compare these data with the freeze frame data.
• Inspections take into account the fact that the malfunction may not have reoccurred and place emphasis on checking the vehicle conditions present at the time when the malfunction occurred.
• When performing inspections, jiggle the relevant wire harnesses and connectors in an attempt to reproduce malfunctions that do not always occur.
Inspection flow:
Using freeze frame data, narrow down the parts to be inspected according to the vehicle conditions at the time when the malfunction occurred.

Thanks much..
I tried to get the freeze frame from OBD2 scanner (LAUNCH) but there was nothing stored.
The LAUNCH CRP129X showed the fault in the DIAGNOSIS section, but when I went to OBD2 section there were no faults,
Anyway I cleared it and I will keep an eye on it. I also did a visual inspection for mice or chewed wires (luckily noting found).
I remember I left the truck go to like 7 miles of range on the gas tank. Maybe this triggered it. as the literate said it could be user action that triggers the code, like running out of gas, but I did not run our of gas completely.

Thanks ...

Looks like you're hitting the far end of the warranty period. Taking it to the dealer?

I try to do all the maintenance myself.
I try to avoid dealer as much as possible.