Malfunctions are detected using checksum techniques for verifying data.
Digital data is composed of zeros and ones. A checksum is the total of all ones in a string of data.
By comparing the checksum value with a stored value, a malfunction can be detected.
If an overrun occurs during normal operation, the microcontroller will be monitored when the following test conditions have been fulfiled :
Ignition start has not occurred.
Accelerator pedal not actuated.
Cruise control is not active.
No increase in external fuel quantity command.
If the ECM microcontroller generates threshold value, the ECM judged this as a fault and DTC is set.
Item | Detecting Condition | Possible Cause |
DTC Strategy | ● Rationality check | ● Faulty ECM |
Enable Conditions | ● Ignition on | |
Threshold Value | ● Case 1: microcontroller is reported as defective (recovery occurred (new program start)) ● Case 2: injector is energized as engine while engine speed above 2050 rpm and APS is 0 % (fuel cut range) ● Case 3: engine speed has not dropped below 500 rpm within 1.5 sec. after turning the iginition switch off (Watchdog post-run test) ● Case 4: Gate array communication error occurs | |
Diagnostic Time | ● Case 1: 0 sec. ● Case 2: AT 0.84 sec. MT 0.49 sec. ● Case 3: 0 sec. ● Case 4: 0.3 sec. | |
MIL Fuel Limit Fuel Cut EGR Off | ● No ● Yes (case3) ● Yes (case 1,2,4) ● No |
