Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

2009 Toyota Prius BaseFACTORY OEM SERVICE PROCEDURE

On-Vehicle Inspection

NOTE:

Perform the MAF meter inspection according to the procedures below.
Only replace the MAF meter when both the LONG FT#1 value and MAF value in the DATA LIST (with the engine stopped) are not within the normal operating range.

CHECK MASS AIR FLOW METER
1. Read value using Techstream (MAF).
  NOTE:
  - Turn off the engine.
  - Perform the inspection with the vehicle indoors and on a level surface.
  - Perform the inspection of the MAF meter while it is installed to the air cleaner case (installed to the vehicle).
  - During the test, do not use the exhaust air duct to perform suction on the exhaust pipe.
  1. Turn the power switch on (ACC).
  2. Turn the power switch on (do not start the engine).
  3. Turn the Techstream ON.
  4. Enter the following menus: Powertrain / Engine and ECT / Data List / MAF.
  5. Wait 30 seconds, and read the values on the Techstream.
    Standard condition:
    
    Less than 0.07 g/sec.
    - If the result is not as specified, replace the MAF meter.
    - If the result is within the specified range, inspect the cause of the extremely rich or lean air fuel ratio (see DTC P0171 SYSTEM TOO LEAN (FUEL TRIM); DTC P0172 SYSTEM TOO RICH (BANK 1) ).

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Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.