The HECU send requirement data, such as Torque reduction, the number of fuel cut cylinders, and TCS control requests, to the Engine ECU ＆ TCU through CAN bus line. The Engine ECU performs fuel cut functions according to requests from the HECU and retards ignition timing by torque reduction requests. The TCU maintains current gear positions during TCS control time, in order not to increase power which causes a Kickdown shift.
Under normal conditions, the inlet valves of all four wheels are not closed during control for longer than 1,28s or If the controller requests pressure-hold or pressure-decrease for longer than 1,28s, a fault is detected. The ABS/ESP warning ramp is turned ON and the EBD warning ramp is turned OFF.
Item | Detecting Condition | Possible cause | |
DTC Strategy | ● Signal monitoring | ● Faulty HECU | |
Case 1 | Monitoring Period | ● Continuous | |
Enable Conditions | ● If the controller requests pressure-hold or pressure-decrease for longer than 1,28 s, a fault is stored. | ||
Case 2 | Monitoring Period | ● Continuous (at vehicle reference speed ＞ 6 m/s, no detected under voltage and a fault is not already detected) | |
Enable Conditions | ● The monitoring reports a failure if continuous ESP control occurs for a time period ＞= 10 s. | ||
Fail Safe | ● The ABS/ESP functions are inhibited, allow the EBD control. ● The ABS/ESP warning lamps are activated. | ||
Ignition "OFF".
Engine "ON".
Does warning lamp remain On?
▶ Substitute with a known-good HECU and check for proper operation. If problem is corrected, replace HECU and then go to "Verification of Vehicle Repair" procedure.
▶ Fault is intermittent caused by faulty HECU or was repaired and HECU memory was not cleared. Go to the applicable troubleshooting procedure.
After a repair, it is essential to verify that the fault has been corrected.
Connect scantool and select "Diagnostic Trouble Codes(DTCs)" mode
Using a scantool, Clear DTC.
Operate the vehicle within DTC Detecting Condition in General Information.
Are any DTCs present ?
▶ Go to the applicable troubleshooting procedure.
▶ System performing to specification at this time.
