GM Historic (OBD I) Diagnostics

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.

5

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.

GM Function List

?

4)Record

Data

]

5)Review

Data

[

` 6)Field Service

~

*Test

Availability*

 

Does

Your

CHECK

 

ENGINE Light Flash?

 

<Yes>

No

~

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

Field Service: Off ?

Press

ENTER

To

Turn

Field

Service

On

~

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.

5 – 8 • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

Page 70
Image 70
Actron 9640 user manual Field Service, Check, Enter

9640 specifications

The Actron 9640 is a distinguished automotive diagnostic tool that has garnered attention for its versatility and user-friendly design. Designed for professional mechanics and DIY enthusiasts alike, the Actron 9640 stands out for its comprehensive features and advanced technologies that simplify vehicle diagnostics.

One of the main features of the Actron 9640 is its ability to read and erase diagnostic trouble codes (DTCs) for a wide variety of vehicles. This tool supports OBD II protocols, allowing it to communicate with a vast array of vehicles produced after 1996. The device provides clear, detailed descriptions of any trouble codes, enabling users to quickly identify and address issues. This is vital for efficient troubleshooting and ensures that users can make informed decisions about repairs.

Another significant advantage of the Actron 9640 is its built-in memory. The device can store code definitions and repair solutions for easy reference during diagnostics. Additionally, it features a robust data logging capability, allowing users to capture live data in real-time, which is essential for performing thorough diagnostic evaluations. This functionality helps in monitoring engine performance, thereby assisting in pinpointing issues that may not always trigger a check engine light.

The Actron 9640 also incorporates a user-friendly interface, equipped with a large LCD display that presents information in an easy-to-read format. Its intuitive navigation and menu options cater to users of varying expertise, making it accessible to beginners while still offering the depth of features that seasoned professionals rely on.

In terms of connectivity, the Actron 9640 is designed to be compatible with various vehicles, supporting multiple protocols beyond OBD II, including CAN, J1850, and ISO9141. This broad networking capability ensures that the device can diagnose problems across different car brands and models.

Built with durability in mind, the device features a robust housing that can withstand the rigors of a workshop environment. The ergonomic design ensures a comfortable grip during use, making it practical for extended periods of diagnostics.

Overall, the Actron 9640 combines advanced features, comprehensive functionality, and ease of use, making it an excellent choice for anyone looking to conduct reliable automotive diagnostics. Whether you're a professional mechanic or a casual car owner, the Actron 9640 can help you maintain your vehicle's performance effectively.