Tach Pulse (RPM) Signal

Connect a "Scan" tester to the ALDL diagnostic connector. RPM should be indicated on tester when engine is cranked or 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.