PeachParts Mercedes-Benz Forum - View Single Post

MB-Dude · #1 11-15-2007, 06:24 PM

Today, I replaced the MAP Sensors for both Banks. No change in status - Bank 2, O2 Sensor 1 still reports 0v output and, of course, the ECU's are still 'Not Ready'. Both fuel systems report closed loop, but a fault with at least one O2 Sensor.

Question #1: The Oxygen Sensor used in this vehicle (Bosch p/n 13638) has four wires. Presumably, 2 wires are four the heater and 2 wires are for the probe. Can anyone confirm which wires are which, or point me in the right direction to find the information?

I want to begin moving along the wiring harness connection-by-connection (the word I’m think of rhymes with ‘yuck’), until I get to the ECU connector. First place to start is at the O2 Sensor itself.

Question #2: If the heater for the O2 Sensor were not to energize for whatever reason is there enough heat in the exhaust to activate the sensor?

I suspect so. However, I have been reading the Bosch Fuel Injection & Engine Management book and one of the things mentioned is that O2 Sensor output is zero if not enough heat is present. The only contradictory observation is that I have monitored both O2 Sensors when the engine is cold. OBDII reports Bank 1 at 0.5v and Bank 2 at 0.0v.

Out of desperation, I even swapped the battery with my other SL, and even the bullet-proof W123. Obviously, that was an exercise in futility.

Does ANYONE have ANY ideas? Anything? I feel I’m wasting my time documenting all this.

Cheers,
Jeff