Hi there I need help figuring out what engine code 41 is and how can I go about making it go away on my 1987 Trans Am with the carbuerated 305 LG4 engine.

This code does not make my SES light illuminate but when I jump pins A and B or use a snap on MT2500 scanner I discover that the code 41 is stored. My scanner says code 41- EST circuit- No distributor reference pulses to the ECM at specified engine vacuum.

I have a new ignition module installed as well as a new MAP sensor. The Map sensor is connected to a vacuum port on the carb. I thought replacing both of these would have helped but not look in clearing the 41. Can anyone advise?

Thanks

 

Verify that the port on the carb used for the MAP sensor is not a timed port. Typically the MAP should be connected directly to a fitting on the intake, but a port on the carb is acceptable IF the port is true manifold vacuum, as in those ported to the lower well in the throttle body.

 

Have you tried disconnecting the battery and resetting the ECM? Just to see if it comes back.