STEP 1. Check harness connector D-38 at heated oxygen sensor (rear) for damage.
STEP 2. Check the heated oxygen sensor (rear).
(1) Disconnect heated oxygen sensor (rear) connector D-38 and connect test harness special tool, MB991658, to the connector on the heated oxygen sensor (rear) side.
(2) Measure the resistance between heated oxygen sensor connector terminal No. 1 and terminal No. 2.
(3) Standard value: 4.5 - 8.0 Ω [at 20°C (68°F)]
Is the measured resistance between 4.5 and 8.0 Ω [at 20°C (68°F)]?
Go to Step 3. Replace the heated oxygen sensor (rear). Then go to Step 11.
STEP 3. Measure the power supply voltage at heated oxygen sensor (rear) harness side connector D-38.
(1) Disconnect the connector D-38 and measure at the harness side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal No. 1 and ground.- Voltage should be battery positive voltage.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is battery positive voltage (approximately 12 volts) present?
Go to Step 5. Go to Step 4.
STEP 4. Check harness connector A-37X at MFI relay for damage.
STEP 5. Check harness connector B-26 at ECM for damage.
STEP 6. Measure the power supply voltage at ECM connector B-26 by using power plant ECU check harness special tool MB992110.
(1) Disconnect all ECM connectors. Connect the power plant ECU check harness special tool MB992110 between the separated connectors.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal No. 35 and ground.- Voltage should be battery positive voltage.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is battery positive voltage (approximately 12 volts) present?
Go to Step 7. Check harness connectors A-17 and C-28 at intermediate connector for damage, and repair or replace as required. Refer to GROUP 00E, Harness Connector Inspection . If intermediate connectors are in good condition, repair harness wire between heated oxygen sensor (rear) connector D-38 (terminal No. 2) and ECM connector B-26 (terminal No. 35) because of open circuit or short circuit to ground. Then go to Step 11.
STEP 7. Check harness connector A-37X at MFI relay for damage.
STEP 8. Check for harness damage between MFI relay connector A-37X (terminal No. 2) and heated oxygen sensor (rear) connector D-38 (terminal No. 1).
STEP 9. Check for harness damage between heated oxygen sensor (rear) connector D-38 (terminal No. 2) and ECM connector B-26 (terminal No. 35).
STEP 10. Check the trouble symptoms.
STEP 11. Test the OBD-II drive cycle.
(1) Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 2 . (2) Check the diagnostic trouble code (DTC).
Is DTC P0037 set?
Retry the troubleshooting. The inspection is complete.