Faulty Powertrain Control Module (PCM)
Faulty Transmission Control Module (TCM)
Engine Light ON (or Service Engine Soon Warning Light)
This diagnostic checks the validity and availability of the gas pedal position signal which is sent by the Powertrain Control Module (PCM) via a CAN message. The diagnostic checks the validity by performing a CRC and message counter check to verify the gas pedal position signal is continuously updated by the PCM and that it has a valid value. The diagnostic also checks the availability by checking the received valid bit. A signal toggle bit and a signal parity bit are sent by the PCM within the CAN message. In order to be sure the message is continuously updated, the value of the toggle bit changes from 0 to 1 and vice versa every two messages. In order to be sure the message is valid, the parity bit value is set so that the sum of specific signals bits (the PDL_POS) of the message content plus the toggle bit plus the parity bit is an even number. If the toggle bit value does not change or the signal parity is not verified for a calibrated amount of time then the Diagnostic Trouble Code (DTC) U11D4 is set or when the signal is not available, the PCM sends a SNA default value to the TCM. If the TCM reads this value then DTC U11D4 is set.