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 MANUALSGMC1995FORWARD CONTROL 4.3 Z, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/CODES - 5.7LTROUBLE CODE CHARTSDTC 43: KNOCK SENSOR WITH SPARK CONTROL MODULENOTES
1995 GMC Forward Control 4.3 Z, Standard
DTC 43: Knock Sensor With Spark Control Module: Notes
1995 GMC Forward Control 4.3 Z, StandardSECTION Notes
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- If conditions for a Code 43 exist, scan tester will display YES. A knock signal should exist at idle unless an internal or system problem exists.
- Determines if system is functioning. Usually, a knock signal can be made by tapping on exhaust manifold. If knock signal is not made, try tapping on engine block near sensor. On models with automatic transmission, it may be necessary to place gear selector lever in Drive.
- Because Code 43 sets when signal voltage on spark retard line remains low, this test should cause signal on that line to go high. The 12-volt signal should be seen by control module as a "no knock" signal if control module and wiring are okay.
- This test determines if knock signal is detected on sensor-to-controller line or if ESC module is at fault.
- If sensor line is routed too close to secondary ignition wires, ESC module may see interference as a knock signal.
- This checks ground circuit to module. An open ground will cause voltage on monitored line to remain constant at about 12 volts. This would cause Code 43 functional test to fail.
- This should generate a knock signal to controller. This determines if ESC controller is operating correctly.
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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.