Jump to content


Photo

O2 Sensor heater circuit and VDC problem

VDC O2 heater circuit

  • Please log in to reply
1 reply to this topic

#1 Gilly

Gilly

    New Member

  • Members
  • Pip
  • 1 posts

Posted 02 April 2017 - 03:22 PM

I  bought my first Subaru about a month ago! It's a 2002 Outback 3.0 Australian model. However, there are a couple issues that I have been trying to track down. 

 

1) The guy I bought it from told me that the O2 sensor had just been replaced and that the CEL needed to be reset. I reset the light but it came back immediately. It is a P0031 and P0051 which is the heater circuits for the front sensors. I believe that they were new sensors but they were a cheap brand so I sourced some OEM (which is Denso, right?) sensors from a junk yard. I still have the same problem. I checked as many grounds as I could fine and they all seemed pretty clean. Now I'm wondering if it is a relay. I have been looking over the manual a bit but I can't decipher which relay controls the heater circuit. Does anyone know or have other suggestions?

 

2) The other issue is the ABS and VDC lights on the right hand side of the dash are on. I was on a rough dirt road a few days ago and the two lights on the right side of the dash turned off and the "VDC OFF" light on the left hand side of the dash came on. To me that means it probably isn't an ABS sensor but I'm just guessing. The guy I bought it from told me it needed a new VDC control module but I can't find much info on that or where it is. I was wondering if it is integrated with another computer somewhere. Any ideas?

 

Unfortunately in Australia I can't finish registration without these issues fixed. Any help is greatly appreciated.

 

-Tyler



#2 NQRSoobee

NQRSoobee

    Trusted Member

  • Members
  • PipPip
  • 132 posts
  • Gender:Male
  • Location:Adelaide

Posted 20 April 2017 - 09:23 PM

Dunno if it will help but I found a quick test procedure for O2 Sensors which helps identify where the problem is:

 

 

Test procedure:

    With ignition on but the engine off use a voltmeter to check for +12 V being supplied to the O2 heater element.  The best location to check for +12 V is after the fuse on the O2 heater circuit.  In fact the closer to the O2 sensor when checking the voltage the more of the circuit between the battery and the O2 sensor is checked.

    If there is no voltage present on the +12V O2 circuit then repair problem could be either an open or short circuit in the +12 V feed circuit. Check if the fuse has blown which will indicate if it is a short circuit.

    If the +12 V feed is okay then disconnect the ground (control) circuit at the other end, usually at or near the ECM wiring connector, and check for resistance in the ground circuit.  If there is infinite resistance in the ground circuit then it is open circuit.

    Finally if the resistance of the O2 heater circuit is above 10 Ohm and the control circuit is good then suspect a bad O2 sensor. Replace the sensor and recheck.






0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users