When the ignition switch was turned ON, or when the ECM determines whether it is an error of RAM in ECM or not, the ECM conducts a single communication. If any one of the following status occurs in the communication, the ECM conducts one more communication. While the ECM is conducting the communication, if (a) is duplicated 20 times continuously, or if (b) is duplicated 20 times continuously, or if (c) is duplicated 2 times continuously, the ECM outputs the OBD2 code P1670.
1. There was a communication error when receiving data.
2. Data sent from the injection pump correction unit does not match to the data received from the ECM.
3. Data received from the pump ROM is not input in the period of 1024 msecond.
Although the determining process is completed without a problem, the ECM conducts the communication again if an undefined code is found while checking an identification code of the receiving data. If the undefined code was duplicated 20 times in a row, the ECM outputs the DTC.