Ignition Control

IGNITION CONTROL (IC)
When the system is running on the ignition control module, that is, no voltage on the bypass line, the ignition control module grounds the Ignition Control (IC) signal. The PCM expects to see no voltage on the IC line during this condition. If it sees a voltage, it sets DTC 42 and will not go into the IC mode.
When the RPM for IC is reached (about 400 RPM), and bypass voltage is applied, the IC should no longer be grounded in the ignition control module so the IC voltage should be varying.
If the bypass line is open or grounded, the ignition control module will not switch to IC mode so the IC voltage will be low and DTC 42 will be set.
If the IC line is grounded, the ignition control module will switch to IC, but because the line is grounded there will be no IC signal. A DTC 42 will be set.
DTC 42 sets if there is an open or a short to ground in the IC or bypass circuit. Refer to CODE 42 IGNITION CONTROL CIRCUIT.
Powertrain Controls - ECM/PCM

KNOCK SENSOR (KS) SYSTEM
DTC 43 sets if there is an open or short to ground in the circuit.
If the conditions for DTC 43 are present, the scan will always display "YES." There should not be a knock at idle unless an internal engine problem, or a system problem exists. Refer to CODE 43 KNOCK SENSOR CIRCUIT.
Powertrain Controls - ECM/PCM

DISTRIBUTOR REFERENCE SIGNAL
The distributor reference signal is covered in the DISTRIBUTOR IGNITION SYSTEM CHECK.
System Check - Distributor Ignition (DI)