Code 43: Electronic SPRAK Control: Notes

WARNING: This page is about a different car, the 1990 Oldsmobile Cutlass Cruiser, 1990 Oldsmobile Cutlass Ciera, 1990 Oldsmobile Cutlass Calais, 1990 Buick Skylark, and 1990 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.

The ECM supples a 5-volt reference on knock sensor signal line. Internal sensor circuitry will cause this voltage to pull down to about 2.5 volts DC. The knock sensor produces an AC voltage signal when knock occurs. This AC voltage signal will ride on the DC signal back to the ECM. Code 43 will set if voltage on circuit No. 496 is greater than 3.5 volts or less than 1.5 volts and this condition is met for 20 seconds.

NOTE: Test numbers refer to test numbers on diagnostic chart.

If a Code 43 is detected, the ECM will retard spark timing by 10 degrees. If an audible knock is heard from the engine, repair the internal engine problem. Normally, no knock should be heard at idle.
The ECM has a 5-volt pull-up resistor which places a 5-volt reference on the knock sensor signal line.
This tests if the knock sensor is faulty or if the ESC portion of the MEM-CAL is faulty.