Diagnostic Circuit Check
Diagnostic circuit check is the starting point for identifying fuel injection system problem. ECM uses CHECK ENGINE light to flash 2-digit codes. If Code 12 is flashed, self-diagnostic system is working.
If fault codes are stored in memory, they will each be flashed 3 times, starting with the lowest code number. If no fault codes are stored, Code 12 will flash until fuse is removed from fuse block.
Record all fault codes. If only Code 12 is flashed, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section. If engine cranks but will not start, see BASIC TESTING article in the ENGINE PERFORMANCE Section.