DIAGNOSIS Required Special Tools: • MB991958: Scan Tool (MUT-III Sub Assembly) MB991824: V.C.I MB991827: USB Cable MB991911: Main Harness B • MB991316: Test Harness Set

STEP 1. Using scan tool MB991958, check data list item 69: Heated Oxygen Sensor Bank 1, Sensor 2 (right 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 69, Heated Oxygen Sensor Bank 1, Sensor 2 (right rear). • Warm up the engine. When the engine is revved, the output voltage should repeat 0 volt and 0.6 to 1.0 volt alternately. (4) 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: Go to Step 2.

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

(1) Disconnect the right bank heated oxygen sensor (rear) connector E-47 and connect test harness special tool, MB991316, to the connector on the right 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 right bank 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 right bank heated oxygen sensor (rear). Then go to Step 5.

STEP 3. Check connector E-47 at right bank heated oxygen sensor (rear) and connector C-91 at PCM for damage.

Q: Is the connector in good condition? YES: Go to Step 4. NO: Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 5.

STEP 4. Check for short circuit to ground between right bank heated oxygen sensor (rear) connector E-47 (terminal No. 4) and PCM connector C-91 (terminal No. 74).

NOTE: Check harness after checking intermediate connector, C-79 and E-45. If intermediate connector is damaged, repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Q: Is the harness wire in good condition? YES: Replace the PCM. Then go to Step 5. NO: Repair it. Then go to Step 5.