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

STEP 1. Using scan tool MB991958, check data list item 59: Heated Oxygen Sensor (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 (rear). (4) Warm up the engine. • Warm up the engine. When the engine is revved, the output voltage should repeat 0 volt and 0.6 to 1.0 volt alternately. (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 - How to Cope with Intermittent Malfunctions . NO: Replace the heated oxygen sensor (rear). Then go to Step 2.