Tach Pulse (RPM) Signal

Use a Scan tester connected to ALDL connector of vehicle to check for a tach pulse signal. RPM should be indicated on tester when engine is being cranked or is running. Tach pulse (RPM reference) is indicated as a voltage signal when a DVOM (minimum 10-megohm input impedance) is touched to circuit No. 430 ECM terminal. See Figure - Figure .