Diagnosis & Testing: Notes

The Diagnostic Circuit Check is an organized approach for identifying fuel injection problems using the Assembly Line Data Link (ALDL). This communication link can provide diagnostic information for display on any "Scan" tester designed for this purpose. If the "Scan" tester is not operating, check tester on another vehicle. If okay, the cigar lighter socket should be checked for 12 volts and a good ground. With the ignition on, if the "Scan" tester reads "NO DATA" or "NO ALDL", check the serial data wire for an open or short to ground. Also check for an open diagnostic "test" terminal "B". Refer to appropriate CHART A-1 schematic for circuit wiring reference. See TROUBLE SHOOTING in the THEORY & OPERATION section of this article for "SCAN DATA" tables.