Code 41, Ignition Signal CKT/No Signal
ECM tach signal is 12 volts, and varies as ignition coil is toggled to ground. ECM uses this signal as a reference to control spark timing. This code is set if there is no signal, or voltage on Brown wire is constant.
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- Checks for B+ on signal line.
- Checks noise suppressor for open.
- Checks for toggling voltage signal.