Code 41, Ignition Signal Circuit No Signal ESA Ignition System: Notes

This ignition system does not use a vacuum advance. The ignition system sends a signal to the ECM. The ECM uses a driver to make the coil fire a spark to the distributor. This is done by a driver which pulls 12 volts from the coil low. When the 12 volts from the coil is pulled low, the ECM looks for a signal. If the signal is not present for more than 2 seconds while cranking, Code 41 will be set. If Code 42 is set at the same time, repair Code 42 first.

1. This simulates a crank signal to the ECM. The ECM will then ground the ignition coil to create a spark.
2. This checks voltage supply to coil.
3. Check for low voltage on ignition coil. The noise suppressor may be shorted to ground.
4. This checks if ECM is shorted to ground in Brown/White wire.
5. High resistance in the coil could cause a low voltage.