Diagnostic Circuit Check: Notes

The diagnostic circuit check is an organized approach for identifying fuel injection problems using an Assembly Line Data Link (ALDL). This data link can provide diagnostic information for display on any "Scan" tester or any tester designed for this purpose. The tester plugs into ALDL connector located below instrument panel. If a stored code is displayed, code definitions will aid in determining if fault is still present (hard failure) or result of an intermittent condition not normally diagnosed using code charts.

If "Scan" tester is not operating, check on another vehicle. If okay, the cigar lighter socket should be checked for 12 volts and a good ground.

Also check for an open diagnostic test terminal for ALDL terminal "B" and ECM. With ignition on diagnostic line (ALDL terminal "B") should have about 5 volts present.