Code 41 - Est Circuit: Notes

WARNING: This page is about a different car, the 1993 Cadillac Fleetwood. However, it is still accessible from the selected car via links, so may be relevant.

When the system is running on the distributor ignition module (no voltage on the by-pass line), the ignition module grounds the ignition control signal. When the RPM for ignition control is reached and by-pass voltage is applied, the ignition control circuit should no longer be grounded in the ignition module, so the ignition control circuit voltage should be varying.

NOTE: Test numbers refer to numbers on diagnostic chart.

Code 41 means the ECM has sensed an open ignition control circuit. This test confirms Code 41 and that the fault causing the code is present.
This step checks for a normal ignition control circuit path through the ignition module.