Battery light on

Using MIL Faults may be retrieved using MIL on instrument panel or scan tool. To activate MIL, turn ignition key ON-OFF-ON-OFF-ON within 5 seconds. Count number of times MIL flashes on and off. This represents the Diagnostic Trouble Code (DTC). Following is a brief description of DTCs and conditions. Ã Â Â Code 12 Battery feed to PCM has been interrupted within last 50-100 engine starts. PCM monitors this circuit whenever ignition is on. Ã Â Â Code 41 Generator field control fails to switch properly. PCM monitors this circuit whenever ignition is on. Ã Â Â Code 44 Battery temperature sensor voltage is out of range. PCM monitors this circuit whenever ignition is on. Ã Â Â Code 46 Charging system voltage is more than one volt above desired control voltage for more than 20 seconds. PCM monitors this signal whenever engine is running. Ã Â Â Code 47 Charging system voltage is at least one volt less than desired control voltage for more than 20 seconds. No significant change in voltage is detected during active test of generator. PCM monitors this signal whenever engine speed is more than 1500 RPM.

My first thought is the vss, vehicle speed sensor. Check for possible trouble codes. You should be able to check mil codes by cycling the ignition switch. You turn the key till the dash lites come on, no further. Cycle the key on--off, on--off, on, then the mil starts flashing, you count the flashes to get the codes. Your looking for two digit codes.

I'd just make sure the battery has a full charge and battery connections are clean and tight on both ends. Usually problems with the speedometer relate to the vss or wiring circuits.

IF the RPM's are getting low enough, that can cause the light to blink on and off. As far as the shaking, check for tune up, check fuel pump pressure, check for vacuum leaks, check the idle air control valve (IAC).