So here's the diagram from the service manual:




I'm trying to check the voltages for the "Power Supply for ECM", which is pins 119, 120. The manual states that it sound read 11-14V with the Ignition Switch: ON.

Also, 121 is the backup for the power supply, which should read 11-14V with the Ignition Switch: OFF.

Ok so my question is, do I read this directly from the harness? What I did was disconnect the harness from the ECU, and try to test the actual connector. However, it doesn't seem to be working that well. So do I need to plug the harness back into the ECU and tap into the individual wire?

 

The answer is you can check it with the ECM harness taken out of the ECM.

Problem was with the wiring diagram was completely *** backwards from what the actual harness looked like.