If he is getting dwell readings the Lambda ECU is getting power and it is working, it just isn't in closed loop. There are tests you can do (grounding the O2 lead or putting 1.5 DC volts on it) to make sure the Lambda ECU is working. Once you prove out the ECU then the O2 sensor is probably bad or the mixture screw is WAY out of adjustment. Refer to D:04:15 for the specific tests. Also read the system notes on the previous page.