Vehicle Application: 1997 Ranger 2.3 Customer Concern: The Check Engine light (CEL) is on, the Powertrain Control Module (PCM) sets Diagnostic Trouble Code (DTC) P1131.
Tests/Procedures: 1. Monitor operation of the #11 Oxygen sensor (O2) voltage input when forcing the engine rich with added fuel such as propane or acetylene. Allow the alternative fuel to enter the engine thru the Mass Airflow Sensor (MAF).
2. When forcing the engine rich with alternative fuel, the O2 sensor reading should jump to a reading of 0.95-1.0 volt. If the #11 O2 sensor voltage changes when the fuel is added but it doesn't jump as high as stated, it is defective whether it is new or not and should be replaced. If the O2 sensor voltage does switch rich as it should, check for intake manifold leaks.
3. If the #11 O2 sensor reading reads 0 volts whether the engine is running rich or not, disconnect the sensor and check the Gray/Light Blue (GY/LB) wire of the sensor harness for an open circuit or short to ground between the sensor and PCM pin 60. If the wiring tests out OK and the sensor does not switch as it should, replace the sensor.
4. If the sensor does switch rich when adding fuel, check the BARO Parameter Identification (PID) on the scan tool. The BARO should read between 150-159 HZ at sea level. If the BARO is low, the PCM will interpret the vehicle at being at high elevation and will cut back on injector pulse width. Try cleaning the MAF sensor, disconnect the battery for at least 10 minutes to clear out the adaptive fuel strategy and perform a relearn test drive. If the BARO drops down low again after the relearn test drive, replace the MAF sensor and retest.
As you can see replacing parts without verifying the problem could cost you a lot of money. Sorry
Potential causes of code P1131. Leaking Engine Vacuum,Contaminated Mass Air Flow (MAF) Sensor,Defective Oxygen (02) Sensor. First thing to try is remove Mass air sensor and clean with a contact cleaner or spray with a non clorinated brake clean spray.
Those relate to fault code only. If you are not getting any fuel pressure at all you may have another problem. One thing that is often overlooked is that fords have a fuel pump shut off switch that cuts pump off in the event of a collision. Have seen fords just get bumped in a parking lot and that safety switch trips. Its usally located inside truck and has a reset button on it. Compotent locater says its .....Located on the toe-board to the right of the transmission hump.