Tachometer Circuit Test

Engine RPM is calculated from crankshaft position sensor input to ECM. Connect Consult-II tester (scan tool) to vehicle. Start engine and monitor consult RPM reading compared to instrument cluster tachometer reading. If RPM readings are the same, tachometer is okay. If readings are not the same, check for engine system trouble codes. See SELF-DIAGNOSTICS - Q45 article in TESTING & DIAGNOSTICS in ENGINE PERFORMANCE. If no engine performance DTCs exist, perform combination meter self-diagnostic check. See ENTERING SELF-DIAGNOSTIC MODE  under SELF-DIAGNOSTIC SYSTEM.