I tought I read somewhere that when testing injector connectors, if you ground the wrong wire (which I may have done) you'll get a voltage reading that begins high and then falls to zero (I experienced this) and it can fry the ECU.

Would this fry the ECU? Could it cause an injector to dump too much fuel and an extreamly rich condition?

 

If you ground the wrong wire (the power side) you'll blow the fuse...

If you ground the other, you're discharging some capacitors inside the ECU for the injector "drivers". You can see the same thing happen while shooting the wire for continuity (on resistance), the meter's battery will charge the caps in the circuit, then they'll discharge, and the resistance reading will fall to 0 ohms (I've done this once just for ***** and grins). Shouldn't hurt anything if you're using a standard meter with a 1.5v or 9v power supply, because the ECU sees voltage from this wire in normal operation...