Ignition "OFF".
Engine "ON".
Does warning lamp remain On?
YES
Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair as necessary and then go to "Verification of vehicle Repair" procedure.
If OK, Substitute with a known-good TCU and check for proper operation. If problem is corrected, replace TCU and then go to "Verification of Vehicle Repair" procedure.
If NG, 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.