Diagnostic Circuit Check - Testing
The Diagnostic Circuit Check is an organized approach for identifying fuel injection problems using an 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 properly, 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 from ALDL terminal "B" and ECM. With ignition on, the diagnostic line should have about 5 volts present.
If no trouble is found, see TROUBLE SHOOTING SYMPTOM DIAGNOSIS in CCC EFI TESTS W/O CODES. Also, see SCAN TESTER USAGE in CCC EFI TESTS W/O CODES and appropriate specification tables in CCC EFI TESTS W/O CODES tables.