P1605Rough idling

• Toyota/Lexus code · Engine
• Turns on the check-engine light

How the car detects it

The engine computer saw the idle speed drop or become unstable. It is a symptom code that often comes with misfire or mixture codes, so diagnose those first.

What you may notice

• Check-engine light
• Shaky idle or idle dips

Likely causes

• PossibleMisfire (spark plugs, ignition coils)
• PossibleAir leak or dirty throttle body
• RareCarbon build-up in the engine

Sources

• static.nhtsa.gov › MC-10132332-9999.pdf · official document
• static.nhtsa.gov › MC-10143946-9999.pdf · official document
• static.nhtsa.gov › MC-10132874-9999.pdf · official document
• toyota-club.net › ems_2zrfe.htm
• toyota-club.net › ems_1nzfxe.htm

Backed by an official manufacturer document.

From Obdaryn's Toyota/Lexus pack, exactly as the app shows it, with the public sources above. Guidance only; confirm with a workshop.