Actron 9640 Manuel D’Utilisation

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If the Scan Tool displays an Error Message, make sure the cables and

adapters are securely attached and the ignition key is ON. Cycle the

ignition key to OFF for 10 seconds, then ON. Attempt the test selected

again. If the problem remains, refer to “Error Messages” on page 9-2.

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Some 1994 and 1995 vehicles use the 16-pin OBD II connector, but are not 

OBD II compliant. They still use the OBD I application software. Refer to 

The Manual Info function instructs the user what section of the manual to use. 

This section covers GM Historic (OBD I) Diagnostics.

The Read Codes function is used to retrieve all stored Diagnostic Trouble 

Codes (DTCs) from the control module(s). This can be performed with key ON 

engine OFF (KOEO) or key ON engine RUNNING (KOER). Two types of codes 

were used by GM in the Historic System: Current codes and History codes. 

Prior to 1986, all codes were referred as Current Codes. From 1986 through 

1995, both codes were used as the PCM was able to differentiate them.

The tool automatically displays the type of codes that pertain to the vehicle 

under test. The DTC types are defined as follows:

• History Codes — intermittent codes placed in the vehicle’s memory when 

the trouble originally occurred, and will remain there even if the trouble has 

been corrected. If no trouble after 50 engine warm-up cycles, the DTC 

erases.

• Current Codes — codes transmitted through the PCM’s data stream when 

a trouble condition is active and cannot be erased. The problem must be 

repaired to remove the DTC.

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On some vehicles, all codes are Current Codes, because the PCM cannot 

distinguish Current Codes from History Codes. The only way to determine 

this is to erase the code and then drive the vehicle to see if the code 

returns.

Perform the following:

1) Set Parking Brake
2) Turn Key On-Engine Off or Running.
3) Put Transmission In Park Or Neutral.