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O2 Sensor Question - P0161

Date: 12/13/2008

Just replaced O2 sensor again had the code removed and with in 10 min after the second start up the C E light was on again. This is the third one since the engine was replaced last year. The young man at auto zone said it was running to rich cause the sensor was jet black. This sensor is the second bank second sensor. The only code they seem to get is for that sensor. What should I be looking at? Thank you in advance.

If it was running rich, the pre-cat sensor would throw a code. Since it is a post cat sensor, I would assume the cat is toast. What is the actual code?

Paul L Fisher

They didn't tell me and I don't see it on the printout they gave me.


Go back and get the actual code and we will help you diagnose.

Where are you located?

Yes people, I ecked but I did this on purpose so we can all help. ;-)

Paul L Fisher

Could this be the code P0161 this is the only # on the print out.




1997 Ford Taurus SHO 3.4L


OBD-II Code Data



HO2S-22 (Bank 2 Sensor 2) Heater Circuit Malfunction


Possible Causes

Setting Conditions

  • HO2S heater power circuit open
  • HO2S heater ground circuit open
  • HO2S signal tracking (due to oil or moisture in the connector)
  • HO2S is damaged or has failed
  • PCM has failed

Engine running for 5 minutes, and the PCM detected an open or shorted condition, or excessive current draw in the heater circuit.
This code sets in 2 Trip(s).






Sounds like a wiring problem if you have changed the sensor. Did you buy the universal O2 sensor or the specific one? What part #?



1997 Ford Taurus SHO 3.4L






1996 - 1998 Ford Taurus 3.0L


1996 - 1998 Ford Taurus 3.4L


MIL Illumination, Possible codes P0135, P0141, P0155, P0161 




P0135, P0141, P0155, P0161 


The driver circuits in the Powertrain Control Module (PCM) are faulty. 

Test & Fix:

MIL Illumination and any combination of codes P0135, P0141, and P0155 indicates a fault in the O2 heater circuits. P0135 is for Bank 1 Sensor 1, P0141 is Bank 1 Sensor 2, P0155 is Bank 2 Sensor 1 and P0161 is Bank 2 sensor 2. The codes are normally set due to driver failures in the PCM. Voltage is supplied to the O2 heaters through the Vehicle Power Circuit (VPWR) circuit. It passes thru the heater element and returned to the PCM to be grounded when heater activation is required. To diagnose, inspect connections and harnesses for damage to the suspect sensor(s). If OK, with Key On, check for battery voltage on the VPWR circuit, Red wire, going to the suspect O2 heater(s). If present, check for control side voltage by gaining access to the PCM and backprobe pin 93, Red/White wire, for P0135; pin 94, White/Black wire, for P0155; pin 95, Yellow/Light Blue wire, for P0141 and pin 96, Tan/Yellow wire for P0161. If OK on suspect sensor(s), disconnect the PCM connector and check circuit resistance between VPWR Pin 97, Red wire, and the suspected control circuit pins. Resistance should be between 3 - 30 ohms with readings likely below 10 ohms. If OK, replace the PCM and retest system.





 Paul L Fisher


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