Replaced Engine Coolant sensor. Had to remove intake manifold, etc. Big job for small part. When finished, won't start. Was running but poorly before. No spark at spark plug. With ignition on, dash lights on, seemingly all gages, etc. working. 12+ volts at fuse no. 5. No voltage or very tiny voltage at pin 6 on the Electronic Control Unit connector. ground wires connected on intake manifold. Seems to be an open between the battery and the ECU, but what? and where? Puzzled.