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I'm going to guess you do No Preventative
Maintenance what so ever, or know what is needed
The Oxygen Sensors get replaced at 100,000 miles
or when they fail or when their switching times & data
are not as it should be
Spark Plugs-every 3 years
It costs money to work on a vehicle to learn how things are
& collect needed data, when it appears to get you places
with no issues,then you have problems & lots of them & no
record of when it did work correctly
O2 Sensors are big part of fuel trim-- IF-- you have no vacuum
leaks or cylinder misifres
An old blocked exhaust converter can be a problem
Replace the spark plugs
Replace all O2 Sensors
Clean the MAF Sensor
Replace any cat over 12 years
Check Fuel Trim
Check to see all 8 Emission Monitors run-- on a long 25
mile road test-after other work is caught up
Exhaust Leaks before converter
Have to check & test it all-the entire vehicle
BEFORE -you replace the cat
code p0128 indicates a mechanical fault ( could be the thermostat stuck open)
code p0174 -system too lean -bank2 ===causes --intake /exhaust leak--fuel pressure/pump--injectors--AIR system--hose connection/s
code po171 refers to system too lean bank 1 same as po174 with the HO2S sensor being the culprit. As to all being related . only by way of the o2 sensors
code p0442 is not connected to the first 3 as it is in a different section of the fuel system
Po137 02 sensor circuir low voltage bank 1 Po171 fuel trim system lean bank 1 p0336 crankshaft oosition sensor A circuit/range oerformance p1404 IAT-B CIRCUIT Malfunctiin/EGR CLOSED PISITION PERFORMANCE
Code Po171 indicates a lean condition on cylinder bank #1 of the engine. This is the drivers side of the engine. I would suggest replacing both front oxygen sensors as a pair to start. An oxygen sensor has a life span of about 5 years and yours are now 9 years old if they are original. When they get older they are slow to respond to changes in the oxygen content of the exhaust and can trigger a code Po171. If you continue to have the same code set after the replacement of both oxygen sensors then it is time to find out why your engine is running lean. Some of the most common causes are an ignition misfire and a vacuum leak. I have also seen Fords EGR flow sensor (known by Ford as Delta Pressure Feedback sensor) to cause problems like that as well. A good mechanic with a scan tool can usually spot a problem like that in a few minutes.
PO121 : TP Sensor Performance = The PCM supplies 5V
to the TP sensor(throttle position). The TP sensor is a variable
resistor that drops the voltage to about 4 volts at WOT(wide open
throttle) to less than 1 volt at closed throttle. Some TP sensors are
adjustable. others have a learn procedure to determine closed
PO171 Fuel Trim System Lean = In closed loop the PCM
adjusts fuel delivery based on H2OS 1 readings and is indicated by
long & short fuel trim values. If lean the PCM will add fuel (fuel
trim above 0%) & if rich the PCM will reduce fuel(fuel trim below
PO128 ECT Below Thermostat Regulating Temperature = possible failed thermostat, low or empty on coolant,
Engine Coolant Temp Sensor, Poor connection/Harness/Wires, faulty PCM Connection.
I think you hit the nail on the head , the ECT Sensor ( which is different than the temp sensor for the dash gauge)
P0171 - Fuel Trim System Lean Bank 1 YOU WILL NEED TO AVE THE DEALER TEST THE O2 SENSOR FOR PROPER SWITCHING, RIGHT NOW IT SHOWS ALWAYS LEAN, THIS MAY BE THE SENSOR OR THE ENGINE MAY REALLY BE LEAN ON FUEL AIR RATIO, AS FAR AS THE SMOKE GOES THE 2 ARE PROBABLY NOT RELATED, HOW MANY MILES ON CAR? IF THE MILES ARE HIGH THEN REPLACE THE O2 SENSOR ON THE CYLINDER BANK WHERE # 1 CYLINDER IS LOCATED, THE SENSOR IS THE ONE BEFORE THE CATALYTIC CONVERTER.