1993 k1500 obd1 43 code

OLDBLUE93 · October 1, 2013

so ive replaced the knock sensor,electronic spark control module, voltage is good ? it throws the code at start up then goes away? dead hores toppic.

timmyleejohnson · November 4, 2013

Circuit Description:
The DTC 43 circuit consists of a knock sensor with one wire that goes directly to the PCM. There are two DTC 43 checks performed by the PCM. One check consists of monitoring CKT 496 for a voltage that is more than 4.5 volts and less than .64 volt.

If voltage is either too high or too low, for 10 or more seconds, DTC 43 will set. Once engine temperature reaches 87.5°C or more, but not over 104°C, MAP above 81 kPa and engine speed below 3200 rpm respectively, the PCM will perform a self check by advancing the timing incrementally while anticipating a knock signal. If no knock signal is received during two consecutive tests, DTC 43 will be set.

Test Description:
Numbers below refer to circled numbers on the diagnostic chart.

The first test is to determine if the system is functioning at the present time.
Test two determines the state of the 5 volt reference voltage applied to the knock sensor circuit.

Diagnostic Aids:
The PCM applies 5 volts to CKT 496. A 3.9K ohm resistor in the knock sensor reduces the voltage to about 2.5 volts. When knock occurs, the knock sensor produes a small AC voltage that rides on top of the 2.5 volts already applied. An AC voltage monitor in the PCM is able to read this signal as knock and incrementally retard spark.

Hope this helps! I love my OBD1 GM truck and want to keep it on the road as long as possible. I see yours has been submerged and still runs (hell yeah!) Good luck!