MIL with DTC’s P0171 and P0172 – 1996-1998 Ford Contour & Lincoln-Mercury Mystique

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  • MALFUNCTION INDICATOR LAMP (MIL) – MIL ILLUMINATED – DIAGNOSTIC TROUBLE CODES (DTCS) P0171 AND P0172 STORED IN MEMORY – VEHICLES WITH 2.0L ENGINE
  • LAMP – MALFUNCTION INDICATOR LAMP (MIL) ILLUMINATED – DIAGNOSTIC TROUBLE CODES (DTCS) P0171 AND P0172 STORED IN MEMORY – VEHICLES WITH 2.0L ENGINE

 

FORD: 1996-1998 CONTOUR
LINCOLN-MERCURY: 1996-1998 MYSTIQUE

 

Malfunction Indicator Lamp (MIL) may be illuminated with Diagnostic Trouble Codes (DTCs) P0171 and P0172 stored in memory.

 

This may be due to silicon contamination of the Mass Air Flow (MAF) sensor.

 

ACTION:

Replace the MAF sensor with a revised MAF sensor.

 

SERVICE PROCEDURE

  1. Use New Generation Star (NGS) Tester or Service Bay Diagnostic System (SBDS) or Scan Tool to determine DTC stored in memory.
  2. If you have any of the following Heated Exhaust Gas Oxygen (HEGO) DTCs: P0131, P0132, P0133 and P0135, proceed to Powertrain Control/Emissions Diagnosis (PC/ED) Service Manual Pinpoint Test H to diagnose those codes. If DTCs P0171 and P0172 are present without any HEGO codes, DO NOT CHANGE THE HEGO SENSORS, but proceed as follows:
    1. Check the air induction system for air leaks or blockages according to PC/ED Service Manual Pinpoint Test HU.
    2. At idle, vehicle in NEUTRAL under normal operating temperature and with all accessories OFF, check the following:
      • 1) Check the barometric reading which should be within ±8 Hz of the normal reading for your altitude. Determine the normal barometric reading for your altitude by referring to the SBDS cart or by measuring, with an NGS, several good vehicles which have been driven that day.
      • 2) Check the MAF voltage which should be no greater than 0.70 volts.
      • 3) Check the long term fuel trim; the NGS Parameter Identification Display (PID) “LONGTI” should not exceed negative 12% (i.e. -13% is out of limit).
  3. If two (2) or more of the above IDLE CHECKS are NOT within range, replace the MAF Sensor (F5RZ-12B579-B). If not, proceed to PC/ED Service Manual Pinpoint Test H for P0171 and P0172 codes.

NOTE: THE BAROMETRIC VALUE DISPLAYED ON NGS/SBDS IS INFERRED BY THE POWERTRAIN CONTROL MODULE (PCM). THE PCM CONSIDERS MANY ELECTRONIC ENGINE CONTROL (EEC) INPUT SIGNALS INCLUDING RPM, MAF AND THROTTLE POSITION TO INFER LOCAL BAROMETRIC PRESSURE. THEREFORE, AFTER A MAF IS REPLACED, THE INFERRED BAROMETRIC READING WILL NOT CHANGE UNTIL THE VEHICLE IS DRIVEN LONG ENOUGH TO ALLOW ADAPTIVE STRATEGY TO RELEARN.

 

PART NUMBER PART NAME
F5RZ-12B579-B MIL with DTC's P0171 and P0172 - 1996-1998 Ford Contour & Lincoln-Mercury Mystique | small light Mass Air Flow (MAF) Sensor

 

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