Question about 1993 Ford Taurus

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CODE 172 ego not switching lean condition

The car has a new cat. o2 sensor, pfe and ECM coding 172 EGO not switching. I am running out of part6s to throw at this car. I am truly stumped.

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  • Brian032472
    Brian032472 Jan 30, 2009

    It seems to run absolutely fine for up to 10 miles without a check engine or any abnormal running conditions. After a start cycle or two it will set the MIL and regardless of the amount of throttle you apply it bogs down miserebly and won't get out of it's own way after you shut it down for two to five minutes it resets the MIL and runs like a champ until it's next fall flat on it's face incident.

  • Brian032472
    Brian032472 Jan 30, 2009

    it has a new fuel pump and fuel filter no issue with fuel pressure either. what does EGO not switching imply?

  • Brian032472
    Brian032472 Feb 01, 2009

    Thanks for your help after the new PCM all cleared finally.


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It is possible you have a leaking injector on that bank. how does the vehicle run?

Posted on Jan 29, 2009

  • warlock61
    warlock61 Jan 30, 2009

    have you checked fuel pressure? When was the fuel filter changed last?


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1 Answer

Which O2 sensor is needed for The code P1135 tOYOTA aVALON 2002

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Well you have done everything. check wiring or replace the ECM. If you took this to a shop. Find another shop.

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I'm sorry you spent that money if this was the original code.

The code means one of the O2 sensors has a faulty heater or the power circuit for the heater is bad. The sensor is not heating up as fast as it should. Since you have replaced the sensor you would need to check the power circuit for the heater.

P0037 SUBARU Description Oxygen Sensors (O2S) or Heated Oxygen Sensors (HO2S) need to reach a minimum operating temperature of 750 degrees F to produce an accurate voltage signal. The faster the heated oxygen sensor reaches that temperature the faster the sensor will start sending an accurate signal to the Engine Control Module (ECM).

In order to achieve the require temperature, a heater element is included inside the heated oxygen sensor. The ECM controls the heated oxygen sensor heater element based on signals from the engine coolant temperature and engine load. The ECM controls the heater element circuit by allowing current flow to ground.

The ECM monitors the voltage signal received through the heater element circuit and determines the state of the circuit by comparing the voltage detected with the factory specifications.
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The easiest way to see if a cat is working is to measure the exhaust temp before and after the cat. If the cat is working the after temp will be less than before. We use an inferred heat gun.
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Have u checked for vacuum leaks or poss leaking EGR valve? use carb spray around the upper intake manifold where it bolts to the lower manifold, spray vacuum lines where they are connected to the engine vacuum ports, the idle speed will change if u hit a leak, as far as the EGR valve goes see if it gets hot at idle, if it does it is leaking, if all checks ok replace the O2 sensor, but i suspect u will find a leak at the upper intake plenum.

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No, it's either a clogged catalytic converter or, more likely, a bad secondary O2 sensor on the driver's side. The secondary sensor is the one after the catalytic converter, which is used to measure its efficiency. When that sensor fails, the computer can't judge how well the cat is working and often throws a code such as this. However, it should also throw a failed O2 sensor, sensor 2 bank 2, at the same time. You may have a bad cat, but if it comes down to replacing parts, I'd do the sensor first - it's about 15% of the price of a cat.

You could take the two secondary sensors and swap them - move the left side one to the right side and vice versa, clear the code, then scan the car again after running and see if the code comes back the same. If it does, your cat is bad. If it comes back reading a problem on bank 1, it's the sensor.

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