Basically this means that an oxygen sensor in bank 1 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1.
Note: This DTC is very similar to P0174, and in fact your vehicle may show both codes at the same time.
Symptoms: You will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a hesitation/surge on acceleration.
Causes: A code P0171 may mean that one or more of the following has happened:
The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
There could be a vacuum leak downstream of the MAF sensor.
Possible solutions include:
In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
Inspect all vacuum and PCV hoses, replace if necessary
Check for a dirty fuel filter and proper fuel pressure
This service should only take 3 to 4 hours, however they may have to order parts overnught, so that may be the reason why they recommend leaving it. Here is the article from Ford.
FORD: 1999-2003
This TSB supersedes articles 03-4-7 and 00-21-8.
ISSUE:
Some vehicles may exhibit a check engine light on and lean Diagnostic Trouble Codes (DTC's) P0171/P0174 (system too lean bank 1 or 2) stored in memory.
ACTION:
Do not replace PCM (Powertrain Control Module), MAF (Mass Air Flow), or HEGOs (Heated Oxygen Sensors), as these parts are not the root cause of the lean codes conditions described. Refer to following Service Procedure for details.
SERVICE PROCEDURE
These conditions may be caused by a loose fitting on the fuel pressure regulator vacuum line on the intake manifold end and/or leaking isolator bolts/port gaskets in the lower to upper intake manifold mounting area. This condition is sometimes intermittent and may not be apparent on a warmed-up engine.
If the vacuum line from the intake manifold to the fuel pressure regulator is loose at the manifold (due to oil contamination), replace the vacuum line (9E498) and install a new design LH service valve cover (6582). Another vacuum leak source is the gasket (9H486) between the upper and lower intake manifold assemblies caused by a loss of tension at the isolator bolt assemblies (9S479) due to contamination of the rubber grommets from excessive oil pullover.
Perform self test, if codes P0171, P0174 are the only codes stored in the PCM then continue with this article. For any other codes, follow the normal diagnostic procedures found in the PC/ED Manual.
(ALL 1999-2003). Reprogram the PCM (Powertrain Control Module) with the latest calibration, WDS B26.2 release or later. Do not replace the PCM. Reset the Keep alive memory.
(1999-2001 ONLY). Inspect the vacuum line from the intake manifold to the fuel pressure regulator for looseness, leaks and/or oil contamination and replace Vacuum Line (XF2Z-9E498-DD) if required.
(1999-2000 ONLY). Inspect the LH Valve Cover, it should be a (3F2Z-6582-BA) Install a new LH Valve Cover if required, refer to Workshop Manual Section 303-01 Valve Cover-LH. (Refer to the following NOTE for description of the old style valve cover).
NOTE: USING A SHOP LIGHT OR FLASHLIGHT, CHECK THE LH VALVE COVER TO SEE IF IT HAS ALREADY BEEN UPDATED TO THE LATEST LEVEL. REMOVE THE PCV VALVE AND RUBBER GROMMET FROM THE VALVE COVER AND LOOK THROUGH THE HOLE AT THE INTERNAL SHEET METAL BAFFLE. THE OLD STYLE VALVE COVER BAFFLE HAS A 3/16" DIAMETER HOLE IN THE 5:00 O'CLOCK POSITION AS YOU LOOK THROUGH THE PCV HOLE (FIGURE 1). VALVE COVERS FITTING THIS DESCRIPTION MUST BE REPLACED.
(ALL 1999-2003). Remove the upper intake and replace only port gaskets (9H486) and isolator bolt assemblies (9S479). The new isolator bolt assemblies use a rubber material that is green in color, do not use the old isolator bolt assemblies with the black rubber material (XF2Z-AA). Do not replace any other intake parts (black plastic or aluminum) or the lower intake gaskets, (9439 and 9A424/425) or the upper intake clamshell gasket (9461). Refer to Workshop Manual Section 303-01, Intake Manifold-Upper.
(ALL 1999-2003). While the upper intake manifold is removed, check the Exhaust Gas Recirculation (EGR) orifices that are pressed into each primary port of the lower intake manifold. If any of the orifices are plugged with soot, clean and unplug them with a pick and solvent.
CAUTION: DO NOT USE SMOKE DETECTION, PROPANE GAS, OR CARB CLEANER TO TEST FOR VACUUM LEAKS. (CARB OR BRAKE CLEANER MAY CAUSE INTAKE MANIFOLD RUNNER CONTROL (IMRC) BEARING FAILURE). SOME LEAKAGE FROM THE IDLE AIR CONTROL (IAC) OR EGR VALVE AND IMRC SEALS IS NORMAL. DO NOT REPLACE THESE PARTS, ESPECIALLY THE LOWER ALUMINUM INTAKE MANIFOLD.
NOTE: THIS CONDITION COULD ALSO BE DUE TO WARM AMBIENT TEMPERATURES AND THE USE OF WINTER GRADE FUELS WHICH HAVE VERY HIGH VOLATILITY AND MAY BOIL IN THE FUEL LINES (VAPOR LOCK) DURING A SHORT HOT SOAK. OXYGENATED FUELS WILL AGGRAVATE THIS CONDITION. IF NON-OXYGENATED FUEL IS NOT AVAILABLE, USE MID/HIGH OCTANE FUELS WHICH HAVE LOWER VOLATILITY AND MAY HELP ALLEVIATE THE CONDITION.
PCM CALIBRATION INFORMATION
Application Old Part Number (-12A650-) Old Tear Tag New Part Number (-12A650-) New Tear Tag Old Calibration New Calibration NGS/WDS Qualifier
1999-2000 49S LEV XF2F-ME ZHT2 YU7Z-EC N/A 9LMA-BEE 9LMA-BEE WDS B26.2 Release or Later
1999-2000 Calif. XF2F-HE NQE2 YU7Z-FC N/A 9LMA-BDE 9LMA-BDE WDS B26.2 Release or Later
1999-2000 Calif. ULEV CAT.RED YF2F-AB FGJ1 YU7Z-GC N/A 0A31AS0B05 0A31AS0B05 WDS B26.2 Release or Later
2001 50S ULEV 1F2F-BD UET3 1U7Z-DBB NYD1 1A31AS0507 1A31AS0512 WDS B26.2 Release or Later
2001 50S ULEV (CAT) 1F2A-AD TVM3 1U7Z-DTA TGA0 1A31NC507 1A31NC0510 WDS B26.2 Release or Later
2002 50S ULEV 2F2A-AC YUX2 2U7Z-AJA JPR0 2A31CA0506 2A31CA0506 WDS B26.2 Release or Later
2002 ULEV (CAT) 2F2A-DB OOZ1 2F2Z-DC OOZ2 2A31ZC0505 2A31ZC0510 WDS B26.2 Release or Later
2003 50S ULEV 3F2A-CB DLQ1 3F2Z-CB DLQ1 3A31BA0505 3A31BA0505 WDS B26.2 Release or Later
Obtain an Authorized Modifications Decal (FPS 8262 - obtainable through DOES II, 25/pkg) and list the date, dealer number, and summary of modifications performed. Select a prominent place adjacent to the Vehicle Emission Control Information Decal suitable for installing the Authorized Modifications Decal. Clean the area, install the decal, and cover it with a clear plastic decal shield.
AUTHORIZED MODIFICATIONS
THE FOLLOWING MODIFICATIONS HAVE BEEN MADE:
Reprogrammed Powertrain Control Module (PCM) Per TSB 03-16-1
THESE MODIFICATIONS HAVE BEEN APPROVED, AS APPROPRIATE, BY EPA AND CARB.
DEALER NUMBER:------------------------------------------DATE:
CHANGE AUTHORITY:
FPS 8262 9/78 FORD MOTOR COMPANY PRINTED IN U.S.A.
PART NUMBER PART NAME
XF2Z-9H486-AA Port Seal - Package of 6 (1 Pkg Req. Per Veh)
3F2Z-9S479-AA Isolator Bolt Assy. - Package of 8 (1 Pkg Req. Per Veh)
XF2Z-9E498-DD Vacuum Line
3F2Z-6582-BA Valve Cover - LH
Good luck.
I would check for vacuum leaks first spray carb clean around intake gasket areas and all vacuum hoses,if the idle changes then there is a leak. you can also remove and clean mass air flow meter using carb clean and a small bristle paint brush.your codes refer to improper air to fuel ratios meaning one is more or less then it should be.by having a dirty mass air flow it will not see the correct air flowing by and it cuts back fuel causing this code to trigger.
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