DIAGNOSIS Required Special Tools: • MB991958: Scan Tool (MUT-III Sub Assembly) MB991824: V.C.I MB991827: USB Cable MB991911: Main Harness B • MD998464: Test Harness

STEP 1. Using scan tool MB991958, check data list item 59: Heated Oxygen Sensor Bank 2, Sensor 2 (left rear).

To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958. (1) Connect scan tool MB991958 to the data link connector. (2) Start the engine and run at idle. (3) Set scan tool MB991958 to the data reading mode for item 59, Heated Oxygen Sensor Bank 2, Sensor 2 (left rear). (4) Warm up the engine. • After increasing the output voltage 0.15 volt or more by the engine revving, finish it. Then confirm that the output voltage reduces to 0.15 volt or less within 3 seconds. (5) Turn the ignition switch to the "LOCK" (OFF) position. Q: Is the sensor operating properly? YES: It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points . NO: Replace the heated oxygen sensor (rear). Then go to Step 2.

STEP 2. Check the left bank heated oxygen sensor (rear).

(1) Disconnect the left bank heated oxygen sensor (rear) connector E-48 and connect test harness special tool, MD998464, to the connector on the left bank heated oxygen sensor (front) side. (2) Warm up the engine until engine coolant 80°C (176°F) or higher.

(3) Perform a tracing for 5 minutes or more with the engine speed of 4,500 r/min. (4) Connect a digital volt meter between terminal No. 2 (black clip) and terminal No. 4 (white clip). (5) While repeatedly revving the engine, measure the heated oxygen sensor (rear) output voltage. Standard value: 0.6 - 1.0 volt • Be very careful when connecting the jumper wire; incorrect connection can damage the oxygen sensor. • Be careful the heater is broken when voltage of beyond 12 volts is applied to the oxygen sensor heater. NOTE: If the sufficiently high temperature (of approximate 400°C or more) is not reached although the oxygen sensor is normal, the output voltage would be possibly low although the rich air-fuel ratio. Therefore, if the output voltage is low, use a jumper wire to connect the terminal No.2 and the terminal No. 1 of the oxygen sensor with a (+) terminal and (-) terminal of 12 volts power supply respectively, then check again. Q: Is the voltage between 0.6 and 1.0 volt? YES: Go to Step 3. NO: Replace the left bank heated oxygen sensor (rear). Then go to Step 4.

STEP 3. Check harness connector E-48 at left bank heated oxygen sensor (rear) and harness connector C-90, C-91 at PCM for damage.

Q: Is the harness connector in good condition? YES: Replace the PCM. Then go to Step 4. NO: Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 4.