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Ford Contour DTC P1131

Q. 1996 Ford Contour four cylinder. The car was showing P0171 until I read your article about the Mass Air Flow (MAF) sensor. I sprayed the two little wires with some aerosol electronic spray. That took out the P0171 code and then the P1131 code came in. Do I change the O2 sensor? What does H02S11 mean?

Ford Contour DTC P1131

A. DTC P1131 indicates the system is correcting RICH for an overly LEAN condition. The Heated Oxygen Sensor (HO2S) voltage is less than 0.45 volts. This is usually due to a vacuum leak after the MAF. It can also be caused by a bad PCV valve or PCV system hose.

It can also be caused by low fuel pressure or a plugged injector.

Ford Contour DTC P1131
Heated Oxygen Sensor Numbering Convention

  • The first oxygen sensor in cylinder bank #1 is numbered HO2S11.
  • The second oxygen sensor in cylinder bank #1 is numbered HO2S12.
  • The first oxygen sensor in cylinder bank #2 is numbered HO2S21.
  • The second oxygen sensor in cylinder bank #2 is numbered HO2S22.
  • Cylinder bank number one is the bank that contains number one cylinder.
  • If a V-6 or V-8 vehicle only uses one downstream Heated Oxygen Sensor (HO2S) it is numbered HO2S12, even if it uses two upstream HO2S.

Additional Information provided courtesy of ALLDATA

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