Causes and Fixes Toyota P1605 Code: Engine Rough Idling

How to fix a Toyota P1605 Code: Engine Rough Idling
A Toyota P1605 Code is set after starting the engine speed drops below 400 rpm or less after 5 seconds.
This code is very similar to other lean codes, such as P0171 and P0174.
A Toyota P1605 code can be hard to troubleshoot as it can be caused by many different things.
If you are getting other codes, they can help point to the cause.
Possible Causes of a Toyota P1605 Code
Intake Air leak
Fuel Related Issue (Fuel Pump/ Clogged Filter)
Bad Sensor (MAF/MAP)
Throttle Body
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