Hi, new on this forum, I have a 98 taurus with a 174 code, low fuel pressure on 2bank, how are these seperated? got a code reader and the software with it says HEGO switch time low, what the heck is this? Is there anywhere to get info on Ford code troubleshooting?
Guess that is enough for now.
Bob

 

Hi Bob..

The 02 sensors are numbered..

11 (bank 1~ position 1) for the engine bank that the #1 cylinder is located on, and 11 being the forward or first sensor in line/exhaust for that side.. Sensor 12 is the one behind or 'after the cat' from the 11 position and sometimes called a catalyst monitor being it’s reading the efficiency of the catalytic converter/s..

Sensor 21 is on the opposite bank of cylinders (from sensor 11), and sensor 22 is behind/after the cat for that bank..

So right bank 02's would be,, 11 and 12,, and left bank 21 and 22 for sensors positions..

The 174 code is for the sensor on the left bank forward/first 02 sensor reading a 'lean condition'.. How the sensors work is,, the sensor monitors the exhaust content leaving the manifold, and the 02 sensors generate a ‘ranging’ voltage from oxygen content/absence of oxygen and the PCM uses the signal to calculate fuel ratio/fuel trim.. The 02 sensors voltage range is about .60 volt, to about .990 give or take.. Low 02 sensor voltages indicate a 'lean' exhaust, and a higher voltage indicates a 'rich' exhaust..

When the sensors are working as they should, and there aren't any vacuum leaks/un metered intake bleeds, low/high fuel pressure issues, injector concerns, ignition, PCV problems, MAF leaks or contamination ect. the sensors will 'continuously' range back and forth in that voltage range (approx. .60-.990) called switching, or cross counts.. The cross counts must happen within a specific time/rate,, if the voltage remains low (lean) for too long, or too high (rich) the check engine light will illuminate and a code will set.. Could be that it’s a sensor failing, but more often than not the code is set because of an engine related issue.. If the pigtail/harness is the same length on both of the ‘forward’ 02’s try and switch their positions left to right.. Disconnect the battery to clear the check engine light, then drive the car as usually.. It may take a few days of driving, but if the check engine light comes back on, read the code again and see if the code changes with the move and sets a P0171 instead.. If so, the 02 is bad.. If not, and the 174 returns then the sensor isn’t the cause for the 174 ,,