2002 GMC Envoy will not start
Have 2002 GMC Envoy SLT 6 cyl 4200 engine. Problem started running rough then stalled. On trying to restart it the Instrument panel went nuts. Speedometer and tach needle rise up and down all light flashing with a noise coming from instrument panel. Thought it was alternator replaced that did not solve the problem. Car will not turn over when you turn key to start. Instrument panel does the same thing at start position any suggestions. Seems to have power. Battery seems OK