Hi, just bought a '96 Tahoe from a British guy and now I'm trying to get it to run smoothly. Main problem is that I cannot read out the error codes. I'm using an Autel AL319 scanner which powers on but cannot communicate with the ECU. I tried two other scanners without success. I checked the wiring of the OBD connector and it looks ok, I also pulled and reconnected all connectors from the ECU, they all looked clean. Maybe a little background: the previous owner decided to go without catalytic converters and bolted on headers and a (nice sounding) Gibson exhaust. When I bought the car it was running badly, I figured that one O2 sensor was missing and the ignition cables were damaged. So I added the sensor and replaced distributor cap and rotor and put on new ignition wires. Check engine light went off and the engine runs far better, but since yesterday the light is back on and I have no idea why. Any suggestions what I can do to read out the error codes? Thanks, Andreas.