Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET1994G 20 VAN V6-262 4.3L VIN ZREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTESTING AND INSPECTIONSCAN TOOL TESTING AND PROCEDURESFAILURE DESCRIPTION AND DIAGNOSTIC TEST REFERALIGNITION CONTROL
1994 Chevrolet G 20 Van V6-262 4.3L VIN Z
Ignition Control
1994 Chevrolet G 20 Van V6-262 4.3L VIN ZSECTION 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)
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)
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.