Actron 9640 Manuel D’Utilisation

With the engine running, the Field Service mode can be used to measure base 

timing, check open loop/closed loop operation, and determine if the engine is 

running rich or lean.

1) Engage parking brake and block drive wheels.
2) Verify engine is cold. If engine is hot or warm, allow it to cool.
3) On scan tool, place Field Service On.
4) Start engine and place transmission in Park or Neutral. The Check Engine 

light will flash once.

5) Warm the engine by idling for 2 minutes at 2000 RPM.
6) Observe Check Engine light.

• If Check Engine light flashes 2.5 times a second, the on-board 

computer is operating in Open Loop.

• When the engine warms up to normal operating temperature, the 

• If Check Engine light...

—   flashes equally ON/OFF, then the fuel system is running normally.
—   is mostly ON, then the fuel system is running Rich.
—   is mostly OFF, then the fuel system is running Lean.

7) On some engines, the spark advance timing is fixed during Field Service 

Mode. This allows the technician to measure the engine base timing.

Refer to “Code Lookup” on page 4-22 of Global OBDII Diagnostics. 

✓

Enter only the code numbers. No system designation is used for historic

DTCs, they are either History or Current codes.

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A “P” appears at the beginning of the DTC if the vehicle uses OBD II type

codes.

Refer to “Print Data” on page 4-20 of Global OBDII Diagnostics.