Diagnostic Circuit Check - With Diagnostic Scan Tool

Fig. 1 "SCAN" DIAGNOSTIC CIRCUIT CHECK:

Fig. 2 ALDL WIRING DIAGRAM:

The "SCAN" Diagnostic Service Check is an organized approach to identify fuel injection related problems using the assembly line communication link (ALCL). This communication link can provide diagnostic information for display on any "SCAN" device or tool designed for this purpose.

The use of a "SCAN" device requires a good understanding of its operations well as its limitations. A complete review of the instruction manual furnished with the tool is very important.

The tool plugs into the ALCL connector below the instrument panel. If a code is displayed, the code definitions will help to determine if the code is still present (hard failure) or the result of an intermitent condition not normally found using the code charts.

A hard failure will be diagnosed using the charts, which can be used with or without a "SCAN" tool. The "SCAN" steps start with the arrow and are identified by the large type. The repair procedures apply to both ways of diagnosis.

With each chart is a wiring diagram

1. If the "SCAN" tool is not working, check it on another car. If god, check the lighter socket for voltage and ground. If the "SCAN" tool reads "no data" or "no ALCL", with the ignition on check the serial data wire for a short to ground or open between the ECM and the ALCL terminal "E". Also check an open diagnostic test terminal from the ALCL terminal "B" and the ECM. With the ignition on the serial data line (ALCL terminal "E") should have a varying voltage of 2 to 5 volts and terminal "B" approximately 5 volts.

The diagnostic circuit check scan data is typical of that displayed by a properly designed and calibrated ALCL scan device.

A scan tool that displays faulty data should not be used and the problem reported to the tool manufacturer. The use of a faulty scan tool can lead to misdiagnosis and the unnecessary replacment of parts.