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Home >> GMC >> 1991 >> Forward Control 6.2 J, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 3 (Engine Controls - Basic Testing) >> C-4, Basic Ignition System Checks (Gasoline) >> 3.8L With C(3)I >> Tach Pulse (RPM Reference) Signal

Tach Pulse (RPM Reference) Signal

WARNING: This page does not describe the selected car, but rather 35 other vehicles, including the 1992 Pontiac Trans Sport, 1992 Oldsmobile Silhouette, 1992 Oldsmobile Bravada, 1992 GMC Yukon, and 1992 GMC Vandura Special. However, it is still accessible from the selected car via links, so may be relevant.

Connect scan tester to 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 (with a minimum 10-megohm input impedance) is used to backprobe circuit No. 430 ECM terminal. For circuit and terminal reference, see appropriate schematic in NO START - ENGINE CRANKS OKAY.