Diagnostic Aids
Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connections or damaged harness. Perform intermittent check by monitoring circuit and code status while wiggling related wiring and connectors. If failure is induced, monitored circuit status will change rapidly and/or related code will set.
If vehicle has non-standard electrical equipment (CB radios, 2-way radios, etc.) check to see if their operation may be causing a 7X resync which may set Code 19. If a "cranks but won't start" condition has existed, code may be due to 20 attempted starts without turning off ignition switch.