Check ECM Output

Start engine. Connect instrument cluster harness connectors. Using DVOM, measure voltage between ground and terminal No. 45 (Blue/Orange wire) at appropriate instrument cluster harness connectors. See Figure or Figure . While observing DVOM, increase engine speed to 2000 RPM, then reduce to idle. Ensure voltage increases with higher engine RPM. If voltage is as specified, tachometer circuit is okay. If voltage is not as specified, check for an open or short in wiring harness between ECM and instrument cluster. Repair as necessary.