[ChevyTech]

A code 43 can cause it to consume more fuel, because if affects spark timing.

Code 43 can be the hardest code to find the cause of. My first suggestion is to pay attention to when the code gets set. When diagnosing it, it is very helpful to know if the code 43 is being set during the self test, or does it get set driving down the road on acceleration when the system is seeing a ping or something rattling on the engine.


CODE 43
Each time the Vehicle is started and certain criteria is met (coolant temp, MAP reading, engine RPM), a self test of the knock senor circuit is run. The ECM adds spark advance while anticipating a knock signal. If no knock signal is detected during the test a code 43 will be set. Some GM manuals state that two consecutive tests must fail for a code to set. (All GM electronic spark timing systems are not the same. Some systems use a separate module between the knock sensor and computer)

Anything that prevents the knock/ping or prevents the system from detecting it will cause a code 43 to be set. A bad knock sensor, ECM failure, wiring, Timing way retarded or a very rich mixture can cause the code.

What many manuals will not tell you is that a code 43 can be set by something loose rattling on or in the engine. Lifters, cam, rod, crank and piston noises all have the potential for causing false knock signals to be produced.

The Knock sensor contains a piezoelectric crystal which causes a voltage to be produced. Loose components on or in the engine can cause the knock sensor to create a voltage and the system may interpret this as pinging. The system retards the timing because it determines it is pinging.

Loose torque converter bolts can cause a false knock signal to be detected.

Clear the 43 trouble code from the ECM memory. Make sure the key is OFF and removing the ECM fuses for tens seconds should clear the code. You could disconnect the battery to clear the code.
Drive the vehicle and try to determine when it sets.