Diagnostic Aids

Control module applies and monitors a 5-volt DC signal to knock sensors. Internal knock sensor circuitry pulls this DC signal down to about 2.5 volts. When knock sensor detects detonation, it generates an AC signal which rides back on DC signal to VCM. Knock signal intensity is dependent upon knock signal level.

Fig 1: Code 43 Schematic (Dual Sensors) Knock Sensor W/O Spark Module

Fig 2: Code 43 Flow Chart (Dual Sensors) Knock Sensor W/O Spark Module

Code 43 can be caused by a faulty knock sensor connection at the ESC module or ECM. Also, check the controller-to-ECM signal line for an open or short to ground.

Fig 1: Code 43 Schematic (3.1L) Electronic Spark Control

Fig 2: Code 43 Schematic (All Except 3.1L, 4.3L Turbo & Models W/4L80-E Transmission) Electronic Spark Control

Fig 3: Code 43 Flow Chart (All Except 4.3L Turbo & Models W/4L80-E Transmission) Electronic Spark Control