Actron 9640 - Manual (Page 70)

GM Historic (OBD I) Diagnostics
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5
Field Service
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.
✓
Some 1994 & 1995 vehicles equipped with a 12-pin ALDL connector with
pins A and B shorted will not cause the CHECK ENGINE light to flash
codes.
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
~