volvo 855T p0172 p0131, O2 sensor?

[henrysin44]

My car has been running very rich and acceleration is less than usual. If I do a computer reset the car runs great for a day then back to running rich and sluggish. The MAF is good or I have 3 bad MAFs lol, I've checked all vacuum hoses, and replaced the temp sensor. I'm going to buy a new Bosch O2 sensor tomorrow unless theres something else I should look for.

[RickHaleParker]

How are you coming up with P0172 and P0131 on a '94 855T?
'94 had the black box blink codes and the codes are in the format X-Y-Z.

[henrysin44]

How are you coming up with P0172 and P0131 on a '94 855T?
'94 had the black box blink codes and the codes are in the format X-Y-Z.

Guess my 94' is weird, I have the blink box and the OBD II port. It is the late model 94'.

[RickHaleParker]

You might want to get a better scan tool. I suggest a Bluetooth ELM357 version 1.4 or higher and 850 OBD-II if you have an Android phone or tablet.

Did you smoke test the EVAP system? It easy to miss a leak just looking around.

Did you clear the codes and see what comes back?

---------------------------------------------
EFI-231 EFI-232 (P0172) Long-term fuel trim. UPPER LIMIT
EFI-231 Long-term fuel trim, part load EFI-232 Long-term fuel trim, idling speed
Diagnostic trouble code (DTC) information EFI-231, EFI-232

Condition
The engine control module (ECM) receives information from the heated oxygen sensor (HO2S) about the fuel/air mixture in the idling and partial load ranges. If the fuel/air mixture deviates from λ=1 the short-term fuel trim will compensate for this by adjusting injection time so that λ=1 is achieved. When the short-term fuel trim makes an adjustment, the integrator median must be adjusted by the long-term trim. If adaptation needs to adjust to close to its maximum diagnostic trouble code (DTC) EFI-232 (idling range -0.48 ms - 0.40 ms) or diagnostic trouble code (DTC) EFI-231 (part load range factor 0.773 - 1.227) and the status message Upper limit (lean fuel/air mixture) or Lower limit (rich fuel/air mixture) will be stored.

Substitute value
none.

Possible source

• Upper limit:
  defective mass air flow (MAF) sensor
  low fuel pressure
  air leakage
  faulty sensor signals.

Lower limit:

• defective mass air flow (MAF) sensor
  high fuel pressure
  leaking injectors
  leaking evaporative emission (EVAP) system
  contaminated engine oil
  oil level too high
  faulty sensor signals.

Fault symptoms
can result in high fuel consumption
may result in poor performance.

-------------------------------------

EFI-212 (P0131) Front heated oxygen sensor (HO2S). Signal too high. Permanent fault

Diagnostic trouble code (DTC) information EFI-212
EFI-212 Front heated oxygen sensor (HO2S), signal

Condition
Before fuel trim starts the front heated oxygen sensor (HO2S) must be ready - it should be at operational temperature and have the correct output voltage. Monitoring of the heated oxygen sensor (HO2S) function starts approximately 3 minutes after heated oxygen sensor (HO2S) heating starts. Diagnostic trouble code (DTC) EFI-212 is stored if there is a fault in the front or rear heated oxygen sensors (HO2S) or their cabling that affects the output voltage from the front heated oxygen sensor (HO2S).

Substitute value
fuel trim disabled
three-way catalytic converter (TWC) diagnostic disabled.

Possible source
Signal too high:

• short-circuit to supply voltage in front heated oxygen sensor (HO2S) signal cable (+)
  short-circuit to supply voltage in front heated oxygen sensor (HO2S) signal cable (-)
  short-circuit to supply voltage in rear heated oxygen sensor (HO2S) signal cable (+)
  short-circuit to supply voltage in rear heated oxygen sensor (HO2S) signal cable (-)
  defective front heated oxygen sensor (HO2S)
  defective rear heated oxygen sensor (HO2S).

Signal too low:

• short-circuit to ground in front heated oxygen sensor (HO2S) signal cable (+)
  short-circuit to ground in front heated oxygen sensor (HO2S) signal cable (-)
  short-circuit to ground in rear heated oxygen sensor (HO2S) signal cable (+)
  short-circuit to ground in rear heated oxygen sensor (HO2S) signal cable (-)
  defective front heated oxygen sensor (HO2S)
  defective rear heated oxygen sensor (HO2S).

Signal missing:

• open-circuit in signal cable (+)
  open-circuit in signal cable (-)
  defective front heated oxygen sensor (HO2S).

Faulty signal:

• short-circuit between signal cable (+) and signal cable (-)
  defective front heated oxygen sensor (HO2S).

Fault symptoms
none.

[abscate]

The heater failure may well be tripping the OXS code, sortsupply, fuse, wiring, and connector before changing OXS

[henrysin44]

You might want to get a better scan tool. I suggest a Bluetooth ELM357 version 1.4 or higher and 850 OBD-II if you have an Android phone or tablet.

Did you smoke test the EVAP system? It easy to miss a leak just looking around.

Did you clear the codes and see what comes back?

---------------------------------------------
EFI-231 EFI-232 (P0172) Long-term fuel trim. UPPER LIMIT
EFI-231 Long-term fuel trim, part load EFI-232 Long-term fuel trim, idling speed
Diagnostic trouble code (DTC) information EFI-231, EFI-232

Condition
The engine control module (ECM) receives information from the heated oxygen sensor (HO2S) about the fuel/air mixture in the idling and partial load ranges. If the fuel/air mixture deviates from λ=1 the short-term fuel trim will compensate for this by adjusting injection time so that λ=1 is achieved. When the short-term fuel trim makes an adjustment, the integrator median must be adjusted by the long-term trim. If adaptation needs to adjust to close to its maximum diagnostic trouble code (DTC) EFI-232 (idling range -0.48 ms - 0.40 ms) or diagnostic trouble code (DTC) EFI-231 (part load range factor 0.773 - 1.227) and the status message Upper limit (lean fuel/air mixture) or Lower limit (rich fuel/air mixture) will be stored.

Substitute value
none.

Possible source

• Upper limit:
  defective mass air flow (MAF) sensor
  low fuel pressure
  air leakage
  faulty sensor signals.

Lower limit:

• defective mass air flow (MAF) sensor
  high fuel pressure
  leaking injectors
  leaking evaporative emission (EVAP) system
  contaminated engine oil
  oil level too high
  faulty sensor signals.

Fault symptoms
can result in high fuel consumption
may result in poor performance.

-------------------------------------

EFI-212 (P0131) Front heated oxygen sensor (HO2S). Signal too high. Permanent fault

Diagnostic trouble code (DTC) information EFI-212
EFI-212 Front heated oxygen sensor (HO2S), signal

Condition
Before fuel trim starts the front heated oxygen sensor (HO2S) must be ready - it should be at operational temperature and have the correct output voltage. Monitoring of the heated oxygen sensor (HO2S) function starts approximately 3 minutes after heated oxygen sensor (HO2S) heating starts. Diagnostic trouble code (DTC) EFI-212 is stored if there is a fault in the front or rear heated oxygen sensors (HO2S) or their cabling that affects the output voltage from the front heated oxygen sensor (HO2S).

Substitute value
fuel trim disabled
three-way catalytic converter (TWC) diagnostic disabled.

Possible source
Signal too high:

• short-circuit to supply voltage in front heated oxygen sensor (HO2S) signal cable (+)
  short-circuit to supply voltage in front heated oxygen sensor (HO2S) signal cable (-)
  short-circuit to supply voltage in rear heated oxygen sensor (HO2S) signal cable (+)
  short-circuit to supply voltage in rear heated oxygen sensor (HO2S) signal cable (-)
  defective front heated oxygen sensor (HO2S)
  defective rear heated oxygen sensor (HO2S).

Signal too low:

• short-circuit to ground in front heated oxygen sensor (HO2S) signal cable (+)
  short-circuit to ground in front heated oxygen sensor (HO2S) signal cable (-)
  short-circuit to ground in rear heated oxygen sensor (HO2S) signal cable (+)
  short-circuit to ground in rear heated oxygen sensor (HO2S) signal cable (-)
  defective front heated oxygen sensor (HO2S)
  defective rear heated oxygen sensor (HO2S).

Signal missing:

• open-circuit in signal cable (+)
  open-circuit in signal cable (-)
  defective front heated oxygen sensor (HO2S).

Faulty signal:

• short-circuit between signal cable (+) and signal cable (-)
  defective front heated oxygen sensor (HO2S).

Fault symptoms
none.

I have an ELM but no idea where it went....or who 'borrowed' it . I did the carb cleaner test on every hose, elbow, and connection with no change in idle (also sprayed around the fuel rail). I also unplugged the MAF and drove around, it seemed to drive worse and when I plugged it back in the engine stalled out so I think its not the MAF.

I have a bunch of ECUs laying around and put a different one in and the O2 code came up instantly, the fuel trim code diddn't come back but that one took a day to pop up.