The ECM monitors a zero pulse and a test pulse from the knock sensors to assure it can still detect knock. This diagnostic runs once per 255 engine cylinder cycles after vehicle is operating in closed loop. This code indicates an error in the knock switch or knock evaluation circuit, both internal to the ECM.

DTC P1602 will set from an internal ECM failure on the knock sensor signal evaluation circuitry.

DTC P1602 is a (type C) DTC.

Record all ECM DTCs and include with repair information.

Replace the ECM.