In a vehicle that has the Direct Ignition System (DIS) or Distributorless Ignition, the PCM (Powertrain Control Module) relies on the data provided by the CKP Sensor (Crankshaft Position Sensor) and the CMP Sensor (Camshaft Position Sensor) to calculate the most appropriate ignition timing, which results in a better speed and load strategy for the engine.
Once the PCM receives the ignition pulse, it is converted into a digital signal that is sent to the ICM (Ignition Control Module), which provides it to the primary winding of the corresponding ignition coil. In this place, the initial pulse is transformed into a much higher pulse for the secondary winding and the combustion process begins.
Although the diagnostic code P1351 OBDII is a manufacturer-specific code, it is most often defined as the Circuit Voltage of the Ignition Control Module. The setting of this code occurs when the PCM detects an out-of-range voltage in the ICM control circuit. This electrical value can be either too high or too low.