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 MANUALSCHEVROLET1987PICKUP V10, 4.3 Z, AUTOMATICREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISCCC TBI TESTS W/CODESDIAGNOSTIC CHARTSCODE 43 - ESC (2.8L/4.3L/5.0L/5.7L) ("SCAN" DIAGNOSTICS)TEST DESCRIPTION
1987 Chevrolet Pickup V10, 4.3 Z, Automatic
Test Description
1987 Chevrolet Pickup V10, 4.3 Z, AutomaticSECTION Test Description
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- If conditions for Code 43 are present, "SCAN" will display "YES". There should not be a knock at idle unless an internal engine problem, or system problem, exists.
- This determines if system is functioning at this time. Usually knock signal can be generated by tapping on right exhaust manifold. If no knock signal is generated, try tapping on block close to sensor.
- Because Code 43 sets when signal voltage on circuit No. 485 remains low, this step should cause the signal on circuit No. 485 to go high. The 12-volt signal should be seen by ECM as "no knock", if ECM and wiring are okay.
- This determines if knock signal is being detected on circuit No. 496, or if ESC module is defective.
- If circuit No. 496 is routed too close to secondary ignition wires, ESC module may see the interference as a knock signal.
- This checks ground circuit to ESC module. An open ground will cause voltage on circuit No. 485 to be about 12 volts. This would cause Code 43 functional test to fail.
- Connecting circuit No. 496 with test light to 12 volts should generate a knock signal. This will determine if ESC module is operating properly.
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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.