Ignition "OFF".
Ignition "ON".
Connect scantool and select "Diagnostic Trouble Codes(DTCs)" mode
Using a scantool, Clear DTC.
Select "Diagnostic Trouble Codes(DTCs)" mode again.
Are any DTCs present ?
YES
▶ 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.
NO
▶ Fault is intermittent caused by faulty HECU or was repaired and HECU memory was not cleared. go to "Verification of Vehicle Repair" procedure.