Hi group. I have an 87 GMC S15 2.5l. It is running lean. I scanned the data stream and saw some interesting readings. The one that concerns me most is the battery voltage. It is reading 0.0V KOEO and 18.5-19.8V at idle. Rev it up a little and that drops to a normal range (~14V) I checked this voltage at the ECM between the battery power and ground and also the ignition power and ground terminals and it is normal all the time. (13-14V) I also checked the other 2 grounds (ENGINE and O2) and they are also good. I have also checked all the grounds under the hood electrically and mechanically and they are also good. Another reading that concerns me is the pulse width. It is reading 300mS! Way too high for normal. I don't think that is even possible but I am going to verify the true PW with a digital scope in a little while. My best guess is a toasted ECM but I am very hesitant to condemn the ECM because of what I have seen in the past. I have never seen one that was actually the cause of the problem.
Any thoughts? Chris M