"Scan" Diagnostic Circuit Check
The "SCAN" Diagnostic Circuit Check is an organized approach for identifying fuel injection problems using an assembly line communication link (ALCL). This communication link can provide diagnostic information for display on any "SCAN" device or tool designed for this purpose.
NOTE:
The following step number refers to the step number in the accompanying flow chart.
- If the "SCAN" tool is not operating, check on another vehicle. If okay, the cigar lighter socket should be checked for 12 volts and a good ground. If the "SCAN" tool reads "no data" or "no ALCL", with the ignition "ON", check the serial data wire for an open or short to ground between ALCL terminal "E" and the ECM. Also check for an open diagnostic test terminal from ALCL terminal "B" and ECM. With ignition on, the serial data line should have a varying 2-5 volts and the diagnostic line about 5 volts.