Actron CP9185 manual From the Diagnostic Codes Menu Select Read Codes

GM Historic (OBD I) Diagnostics

Read Codes

✓ The Read Codes function is used to retrieve all stored DTCs from the control module(s). This can be performed with KOEO or 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 to as Current Codes. From 1986 through 1995, both codes were used because the PCM was able to differentiate between them.

✓ The Scan 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 PCMs data stream when a trouble condition is active and cannot be erased. The problem must be repaired to remove the DTC.

✓ On some vehicles, all codes are Current Codes, because the PCM
cannot distinguish Current Codes from History Codes. The only				5
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) KOEO or KOER.
3) Put transmission in park (P) or neutral (N).
From the Diagnostic Codes Menu:
1.Select Read Codes.
•Use	UP or DOWN arrow		Diagnostic Codes Menu
key until Read Codes is			Read Codes
highlighted.			Erase Codes
			Review Data
•Press	ENTER.
			Print Data
			Code Lookup
✓ The Scan Tool retrieves the DTCs.			Tool Setup

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