Actron 9640 Manuel D’Utilisation

Field Service is a special diagnostic mode to monitor fuel system operation and 

read DTCs. Some GM service manuals may refer to this mode as the Field 

Service Mode Check. This mode works on vehicles equipped with a 12-pin 

ALDL connector with a wire present in Pin-B, Diagnostic or Test Enable. The 

scan tool enters this mode by grounding Pin-B: shorting Pin-B to Pin -A 

(ground). 

Field Service Mode can be operated with the ignition Key On-Engine Off 

(KOEO) or with the Key On-Engine Running (KOER). 

✓

Vehicles equipped with climate control computers do not use Field Service

Mode.

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Select Field Service from the GM 

Function List and press 

ENTER. 

Turn ignition Key On, but do not start 

engine. The Check Engine light should 

flash. Select YES to continue. If the light 

does not illuminate, either the vehicle 

does not support this test mode, the 

lamp is burned-out or circuit problems 

exist.

✓

It is difficult to know exactly which GM vehicles use the Field Service

mode. It is possible to have the Field Service mode function on the

Function List, and it not be applicable.

If Check Engine light operates, the Field 

Service screen is displayed. Pressing 

ENTER will toggle the short to Pins A & 

B On and Off.

Continue with either the KOEO 

procedure or KOER procedure. When done, press 

FUNC to return to the GM 

Function List.

✓

While in Field Service mode, no new trouble codes are stored in the

vehicle’s memory.

GM Function List

?

4)Record Data 

]

5)Review Data

[

` 6)Field Service   ~

*Test Availability*
Does Your CHECK
ENGINE Light Flash?
  <Yes>     No  ~

Field Service: Off ?

Press ENTER To Turn
Field Service On

~