DTC Troubleshooting

DTC TROUBLESHOOTING PROCEDURES

Step	Action	YES	NO
1	Was "Engine and Emission Control System Check" performed?	Go to Step 2.	Go to ENGINE AND EMISSION CONTROL SYSTEM CHECK .
2	A/F sensor heater circuit check Disconnect connector from A/F sensor with ignition switch turned OFF. Check for proper terminal connection to A/F sensor connector. If connections are OK, measure circuit voltage between "Power supply circuit of A/F sensor heater" and vehicle body ground with ignition switch turned ON. Is measured voltage 10 - 14 V?	Go to Step 3.	Repair or replace defective wiring harness / connector.
3	A/F sensor heater circuit check Check that A/F sensor heater control circuit is as follows. Circuit voltage between "Control circuit of A/F sensor heater" and vehicle body ground is 0 V with ignition switch turned ON. Is it good condition?	Go to Step 4.	Repair or replace defective wiring harness / connector.
4	A/F sensor heater circuit check Disconnect connectors form ECM and check for proper terminal connection to ECM connector. If connections are OK, check that A/F sensor heater circuit is as follows. Insulation resistance of wire harness is infinity between "Control circuit of A/F sensor heater" terminal and each other terminal at A/F sensor connector. Wiring harness resistance of "Control circuit of A/F sensor heater" and "Control ground circuit of A/F sensor heater" is less than 1 Ω. Insulation resistance between "Control circuit of A/F sensor heater" and "Control ground circuit of A/F sensor heater" is infinity. Are they in good condition?	Go to Step 5.	Repair or replace defective wiring harness / connector.
5	A/F sensor heater check Check heater resistance of A/F sensor referring to AIR FUEL RATIO (A/F) SENSOR ON-VEHICLE INSPECTION . Is A/F sensor heater in good condition?	Substitute a known-good ECM and recheck.	Replace A/F sensor.