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-   -   300e 2.8, No voltage to the o2 sensor heater (http://www.peachparts.com/shopforum/tech-help/280667-300e-2-8-no-voltage-o2-sensor-heater.html)

my6.3 07-08-2010 01:46 AM
300e 2.8, No voltage to the o2 sensor heater
 
I'm not getting 12 volts to the o2 sensor heater. Looking at the wiring diagram, it looks like the V+ wire goes directly from the sensor heater to pin 30 of the ECM. Does anyone know if there is a relay and/or fuse in this heater circuit?

mbdoc 07-08-2010 08:19 AM
No relay or fuse on that model.

Directly from HFM control unit.

my6.3 07-08-2010 12:12 PM
Quote:
Originally Posted by M.B.DOC (Post 2501240)
No relay or fuse on that model.

Directly from HFM control unit.
That's what I was afraid of. Do you know if there is an operating condition or external signal the hfm unit is looking for that would tell it to shut off that voltage or am i going to be opening up the unit to look for an internal fault if i find no fault in the wiring from the unit?

mbdoc 07-08-2010 12:38 PM
Signal should happen at approx 35C engine coolant temp.

Heater runs all of the time from there.

my6.3 07-08-2010 03:12 PM
Quote:
Originally Posted by M.B.DOC (Post 2501382)
Signal should happen at approx 35C engine coolant temp.

Heater runs all of the time from there.
I assume that's determined(35C) by B11/3?..Any resistance/temperature reference charts available for B11/3 to test it for function?


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