Tach Pulse (Rpm) Signal

The easiest way to check for a tach pulse signal is using a Scan tester connected to the ALDL of the vehicle. RPM should be indicated on tester when engine is being cranked, or is running. Tach pulse (RPM reference will be indicated as a voltage signal when a DVOM (minimum 10-megohm input impedance) is touched to circuit No. 430 ECM terminal. For circuit and terminal reference, see appropriate schematic in NO-START - ENGINE CRANKS OKAY in this article.