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Chris (aka- Moose)
Chris (aka- Moose), Ford Technician
Category: Ford
Satisfied Customers: 33406
Experience:  16 years experience with Ford.
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I have a 1997 Ford Ranger 2wd with a 2.3 4 cyl. The engine

Customer Question

I have a 1997 Ford Ranger 2wd with a 2.3 4 cyl. The engine light comes on and the OBD2 code is P 1131 I've been to two dealerships and it still pops up every so often. I've gotten a lot of theories but no real answer. Was told it could be just an O2 sensor but I don't really want to go swapping parts all willy nilly without a real idea where to go. Any helf would be greatly appreciated! Thanks!
Submitted: 5 years ago.
Category: Ford
Expert:  Chris (aka- Moose) replied 5 years ago.

Hello, I'm Chris, a current Ford Lincoln Mercury employee.

 

Thanks for visiting Just Answer. I will do my very best to help you resolve your concerns by asking questions if needed then suppling a answer. Gaining your TRUST in myself and knowledge is my goal. I try my hardest to respond in a timely matter and I will respond to any reply anytime I am on line.

 

DTC 1131 means the the upstram O2 sensor is not switching. This means it is not able to detect rich or lean conditions. In more detail it really means it sees to much oxygen in the exhaust which means you are sucking air into the engine from anohter location other than the air filter or your not getting enough fuel.

Checks here would be looking for vacuum or PCV hose leaks or intake gasket leaks. Ether sprayed on suspect areas while idleing will increase the idle if a leak is hit. Fuel pressure checks are also needed.

Here is the pinpoint test for this code straight from ford, the same thing all ford techs view to help us.

 

H40 DTCs P1131, P1151, P1132 AND P1152: UPSTREAM HO2S(S) NOT SWITCHING. DTCs P1130 AND P1150: FUEL SYSTEM NOT SWITCHING AT FUEL TRIM (RICH OR LEAN)

    • HO2S-11 = DTCs P1131, P1132 and P1130
    • HO2S-21 = DTCs P1151, P1152 and P1150
    • Excessive fuel pressure.
    • Leaking fuel injector(s).
    • Leaking fuel pressure regulator.
    • Low fuel pressure or running out of fuel.
    • Contaminated fuel injector(s)
    • Air leaks after the MAF.
    • Vacuum leaks (vacuum lines and gaskets).
    • Restricted air inlet.
    • PCV system.
    • Fuel purge system.
    • Improperly seated engine oil dipstick.
    • Leaking gasket.
    • Stuck open EGR valve.
    • Leaking diaphragm.
    • Oil overfill.
    • Cam timing.
    • Cylinder compression.
    • Exhaust leaks before or near the HO2Ss.
  • Diagnostic Trouble Codes (DTCs) P1131 bank 1 (Cylinder 1) and P1151 bank 2 indicate the fuel/air ratio is correcting rich for an overly lean condition. The HO2S voltage is less than 0.45 volt. DTCs P1132 bank 1 (Cylinder 1) and P1152 bank 2 indicate the fuel/air ratio is correcting lean for an overly rich condition. The HO2S voltage is greater than 0.45 volt.

    DTCs P1130 and P1150 indicate the fuel control system has reached maximum compensation for a lean or rich condition and the HO2S is not switching.

    DTC/HO2S Reference List

    Possible causes:

    Fuel system

    Induction system

    EGR System

    Base engine

  • Check intake air system for leaks, obstructions and damage.
  • Check air cleaner element, air cleaner housing for blockage.
  • Verify integrity of the PCV system.
  • Check for vacuum leaks.

Are any of the above concerns present?

Yes No
SERVICE as necessary. COMPLETE PCM Reset to clear DTCs. RERUN Quick Test. GO to H42 .

H41 DTCs P0172, P0174, P0171 AND P0175: FUEL SYSTEM AT THE CORRECTED FUEL TRIM

    • HO2S-11 = DTCs P0171 and P0172
    • HO2S-21 = DTCs P0174 and P0175
    • Excessive fuel pressure.
    • Leaking fuel injector(s).
    • Leaking fuel pressure regulator.
    • Low fuel pressure or running out of fuel.
    • Contaminated fuel injector(s).
    • Vapor management valve (VMV) leaking.
    • Air leaks after the MAF.
    • Vacuum leaks (vacuum lines and gaskets).
    • Restricted air inlet.
    • PCV system.
    • Fuel purge system.
    • Improperly seated engine oil dipstick.
    • leaking gasket.
    • Stuck open EGR valve.
    • Leaking diaphragm.
    • Oil overfill.
    • Cam timing.
    • Cylinder compression.
    • Exhaust leaks before or near the HO2S(s).
  • Diagnostic Trouble Codes (DTCs) P0171 bank 1 (Cylinder 1) and DTC P0174 bank 2 indicate the fuel/air ratio is too lean. The fuel trim system is at the rich correction limit.

    DTC P0172 bank 1 and DTC P0175 bank 2 indicate the fuel/air ratio is too rich. The fuel trim system is at the lean correction limit.

    DTCs HO2S Reference list:

    Possible causes:

    Fuel system

    Induction system

    EGR System

    Base engine

  • Check intake air system for leaks, obstructions and damage.
  • Check air cleaner element, air cleaner housing for blockage.
  • Verify integrity of the PCV system.
  • Check for vacuum leaks.

Are any of the above concerns present?

Yes No
SERVICE as necessary. COMPLETE PCM Reset to clear DTCs. RERUN Quick Test. GO to H42 .

H42 PERFORM KOER SELF-TEST

  • Key off.
  • Scan Tool connected.
  • Disconnect fuel vapor hose from intake manifold and plug fitting at intake manifold.
  • Start engine and run at 2000 rpm for 5 minutes and return to idle.
  • Perform Key On Engine Running (KOER) Self-Test.

Are any HO2S DTCs P1127, P1128 P1129, P1131, P1132, P1151 or P1152 present?

Yes No
If DTC(s) P1127, P1128, or P1129 are present, GO to Section 4A, Powertrain Diagnostic Trouble Code (DTC) Charts and SERVICE those DTCs first. If DTC(s) P0131 or P0151 are present in Continuous Memory, SERVICE DTC P0131 or P0151 in the order they are displayed. GO to H27 .

DTCs P1131, P1130, or P1151, P1150:

GO to H43 .

DTCs P1132, P1130, or P1152, P1150:

GO to H49 .
For Continuous DTCs Only P1130, P1150, P0171, P0174, P0172 and P0175:

GO to H52 .

If DTC(s) P1132 and/or P1152 are no longer present, RECONNECT fuel vapor line.

Escort/Tracer, Mustang, Thunderbird/Cougar and Ranger/Aerostar with EVAP canister purge valve:

GO to HW18 .

Contour/Mystique, Continental, 5.8L F-Series/E-Series and 7.5L F-Series:

GO to HW10 .

All other EVAP systems:

GO to HX49 .

All others without reoccuring DTCs:

The fault that produced the DTC is an intermittent. GO to Pinpoint Test Step Z1 with the following data: HO2S-11, 21 PIDs and list of Possible causes.

H43 HO2S CIRCUIT TEST (WITH LEAN DTCs)

  • Key off.
  • Scan Tool connected.
  • Disconnect the HO2S related to the DTC. Inspect for damaged or pushed out pins, water, corrosion, loose wires. Service as necessary.
  • Key on, engine off.
  • Access the correct HO2S PID.

    Note: If a spark occurs, remove jumper and go to Pinpoint Test Step H47 (check fuse in the heater circuit).

  • Jumper the HO2S Signal circuit to the HO2S Heater VPWR circuit at the HO2S vehicle harness connector.

Is the reading 1.30 volts or greater?

Yes No
CHECK SIG RTN circuit. GO to H44 . An open or short to ground exists in the vehicle harness or PCM. GO to H46 .

H44 CHECK SIGNAL RETURN CIRCUIT FOR SHORTS AND OPENS

  • Key off.
  • Install breakout box. PCM connected.
  • Measure the resistance between the HO2S SIG RTN terminal at the HO2S vehicle harness connector and the battery ground terminal.

Is the resistance reading less than 5.0 ohms?

Yes No
REMOVE breakout box. GO to H52 . CHECK wiring. GO to H45 .

H45 CHECK HO2S SIGNAL RETURN CIRCUIT IN VEHICLE HARNESS

  • Breakout box installed. PCM disconnected.
  • Measure the resistance between the HO2S SIG RTN terminal at the HO2S vehicle harness connector and the SIG RTN test pin at the breakout box.

Is the resistance reading less than 5.0 ohms?

Yes No
REMOVE breakout box. REPLACE PCM. RERUN Quick Test. SERVICE open circuit. REMOVE breakout box. RERUN Quick Test.

H46 CHECK RESISTANCE OF HO2S AND HO2S GROUND CIRCUITS

  • Key off.
  • Disconnect PCM. Inspect both ends of connector for bent or pushed out pins, corrosion or other damage. Service as necessary.
  • Install breakout box. Leave PCM disconnected.
  • Disconnect suspect HO2S from harness. Inspect both ends of connector for damaged or pushed out pins, moisture, corrosion, loose pins. Service as required.
  • Measure the resistance between HO2S Signal Test Pin at the breakout box and the HO2S vehicle harness connector. Use the Pin assignment below and record the reading:
    • HO2S-11 SIG = Test Pin 60
    • HO2S-21 SIG = Test Pin 87
    • HO2S SIG RTN = Test Pin 91

Is the resistance reading less than 5.0 ohms?

Yes No
GO to H47 . SERVICE open circuit. REMOVE breakout box. RECONNECT PCM and HO2S. RERUN Quick Test.

H47 CHECK HO2S CIRCUIT WIRING HARNESS FOR SHORT TO GROUND

  • Key off.
  • Breakout box installed, PCM disconnected.
  • HO2S disconnected.
  • Measure resistance between the HO2S Signal Test Pin and Test Pins 24, 51, 77, 103 (PWR GND) and 91 (SIG RTN) at the breakout box.

Is each resistance greater than 10,000 ohms?

Yes No
GO to H48 . SERVICE short circuit. REMOVE breakout box. RECONNECT PCM and HO2S. RERUN Quick Test.

H48 CHECK HO2S FOR SHORT TO GROUND

  • Key off.
  • Breakout box installed, PCM disconnected.
  • Reconnect HO2S.
  • Measure resistance between PWR GND and SIG RTN Test Pins and HO2S Signal Test Pin at the breakout box:
    • HO2S-11 SIG = Test Pin 60
    • HO2S-21 SIG = Test Pin 87
    • HO2S GND = Test Pin 24 and 103
    • HO2S SIG RTN = Test Pin 91

Is resistance greater than 10,000 ohms?

Yes No
REMOVE breakout box. RECONNECT HO2S. REPLACE PCM. RERUN Quick Test. REPLACE HO2S. REMOVE breakout box. RECONNECT PCM. RERUN Quick Test.

H49 HO2S CIRCUIT CHECK (FOR RICH DTCS)

  • Key off.
  • Disconnect the HO2S related to the DTC received. Inspect for damaged or pushed out pins, corrosion and loose wires. Service as necessary.
  • Scan Tool connected.
  • Key on.
  • Access the HO2S PID(s).

Is the reading 0.2 volt or less?

Yes No
GO to H51 . A short to power exists. GO to H50 .

H50 CHECK FOR SHORTS TO VOLTAGE SOURCE IN THE HARNESS CIRCUIT

  • Key off.
  • Disconnect Scan Tool from DLC.
  • Suspect sensor disconnected.
  • Disconnect PCM. Inspect for damaged or pushed out pins, corrosion and loose wires. Service as necessary.
  • Install breakout box, leave PCM disconnected.
  • Use the following list to measure the resistance between the appropriate test pins at the breakout box:
    • DTC P1130, P1132=HO2S-11
    • Test Pin 60 and Test Pins 71, 93 and 97.
    • DTC P1150, P1152=HO2S-21
    • Test Pin 87 and Test Pins 71, 94 and 97.

Is the resistance greater than 10,000 ohms?

Yes No
REMOVE breakout box. REPLACE PCM. RERUN Quick Test. REPLACE HO2S. SERVICE short to power. REMOVE breakout box. RECONNECT all components. RERUN Quick Test.

H51 CHECK FOR HO2S SIGNAL SHORTED TO HO2S HEATER CIRCUIT IN THE SENSOR

  • Key off.
  • Suspect HO2S sensor connected.
  • Scan Tool connected.
  • Key on, engine off.

    Note: HO2S displayed as O2S on Scan Tool.

  • Access HO2S PID corresponding to DTCs received.

Is the HO2S voltage greater than 0.45 volt?

Yes No
REPLACE HO2S. RECONNECT all components. RERUN Quick Test. RECONNECT all components. GO to H52 .

H52 CHECK FUEL PRESSURE

    WARNING: THE FUEL SYSTEM IS PRESSURIZED WHEN THE ENGINE IS NOT RUNNING. TO PREVENT INJURY OR FIRE, USE CAUTION WHEN WORKING ON THE FUEL SYSTEM. BECOME FAMILIAR WITH THE WARNING CAUTION AND NOTE IN PINPOINT TEST HC BEFORE SERVICING.

  • Key off.
  • Install fuel pressure gauge.
  • Verify vacuum source to fuel pressure regulator.
  • If engine will start:
  • Start engine and idle. Record fuel pressure.
  • Increase engine speed to 2500 rpm and maintain for one minute. Record fuel pressure.
  • No Start:
  • Cycle key on and off several times. Record fuel pressure.

Is the fuel pressure between 310-415 kPa (45-60 psi) for (2.5L) Contour/Mystique or 207-310 kPa (30-45 psi) for all others?

Yes No
Fuel system is capable of required fuel pressure. GO to H53 . Probe:

Fuel pressure out of specification.

GO to Pinpoint Test KN1 .

All others:

GO to Pinpoint Test HC1 .

H53 CHECK SYSTEM ABILITY TO HOLD FUEL PRESSURE

  • Fuel pressure gauge installed.
  • Cycle key on and off several times.
  • Verify there are no external leaks (service as necessary).

Does the fuel pressure remain within 34 kPa (5 psi) of the highest reading after one minute?

Yes No
For Continuous DTCs P1130, P1150, P0171, P0172, P0174 and P0175:

GO to H54 .

For No Starts:

GO to H55 .

For HO2S DTCs displayed with misfire DTCs: GO to H56 .

Flexible Fuel Taurus:

GO to H56 .

All other DTCs:

GO to H60 .
Excessive pressure loss. GO to Pinpoint Test Step HC4 .

H54 CHECK SYSTEM ABILITY TO HOLD FUEL PRESSURE WITH KEY ON

  • Fuel pressure gauge installed.
  • Cycle key on then off several times.
  • Turn key on and engine off, monitor fuel pressure gauge.

Does the fuel pressure remain within 34 kPa (5 psi) of the highest reading after 10 seconds?

Yes No
For Continuous DTCs P1130, P1150, P0171 and P0174:

GO to H56 .
For DTCs P0172 and P0175:

GO to H58 .

H55 CHECK ABILITY OF FUEL INJECTOR(S) TO DELIVER FUEL

  • Pressure gauge installed.
  • Cycle key several times.
  • Locate and disconnect the Inertia Fuel Shutoff (IFS) Switch.
  • Monitor pressure gauge while cranking the engine for at least five seconds.

Was there a pressure drop greater than 34 kPa (5 psi) while cranking the engine?

Yes No
The Electronic Engine Control System is not the cause of the no start. REMOVE the fuel pressure gauge. RECONNECT the IFS switch. REFER to Section 3A , Symptom Charts, for further diagnosis. REMOVE fuel pressure gauge. RECONNECT IFS switch. GO to H56 .

H56 CHECK RESISTANCE OF FUEL INJECTOR(S) AND HARNESS

  • Key off.

    Note: This erases Continuous Memory DTCs.

  • Disconnect PCM. Inspect for damaged or pushed out pins, corrosion and loose wires. Service as necessary.
  • Install breakout box, leave PCM disconnected.

    Note: If misfire DTCs are displayed with the Fuel Control DTCs, use the misfire DTCs to determine the fuel injector circuits requiring testing.

  • Measure resistance between suspect fuel injector Test Pin(s) and Test Pin 71/97 (VPWR) at the breakout box using the chart below.

    FUEL INJECTOR TEST PINS
    Cylinder NumberTest PinCylinder NumberTest Pin
    175699
    2101772
    374898
    4100968
    5731042

Is the resistance between 11.0-18.0 ohms?

Yes No
Fuel injector and harness resistance is OK. GO to H59 . GO to H57 .

H57 CHECK RESISTANCE OF FUEL INJECTOR HARNESS

  • Key off.
  • Breakout box installed, PCM disconnected.
  • Disconnect fuel injector harness connector at the suspect fuel injector.
  • Measure the resistance between Test Pin 71/97 (VPWR) at the breakout box and the VPWR pin at the fuel injector harness connector.
  • Measure resistance between the Fuel Injector Test Pin(s) at the breakout box and the Fuel Injector Signal Pin at the fuel injector connector. (Refer to chart in H56 for Fuel Injector Pin location.)

Is each resistance less than 5.0 ohms?

Yes No
GO to H58 . SERVICE open harness circuit. REMOVE breakout box. RECONNECT PCM and fuel injectors. RERUN Quick Test.

H58 CHECK FUEL INJECTOR HARNESS CIRCUIT FOR SHORT TO POWER OR GROUND

  • Key off.
  • Breakout box installed, PCM disconnected.
  • Suspect fuel injector harness disconnected.
  • Measure resistance between the fuel injector Test Pin(s) and Test Pin 71 or 97 (VPWR), 24 and 103 (PWR GND) at the breakout box (refer to chart in H56 ).
  • Measure the resistance between the Fuel Injector Test Pin(s) at the breakout box and chassis ground.

Is each resistance greater than 10,000 ohms?

Yes No
GO to H59 . SERVICE short circuit. REMOVE breakout box. RECONNECT PCM and all fuel injector(s). RERUN Quick Test.

H59 CHECK INJECTOR DRIVER SIGNAL

    This test requires a standard 12 volt test lamp.

  • Key off.
  • Breakout box installed.
  • Connect PCM to breakout box.
  • Connect test lamp between Test Pin 71/97 (VPWR) and suspect fuel injector Test Pin(s) (refer to chart in H56 ).

    Note: Properly operating system will show a dim glow at idle on the test lamp.

  • Crank or start engine.

Does test lamp have a dim glow while cranking or running engine?

Yes No
REMOVE breakout box. RECONNECT PCM. GO to H60 . No light/Continuous bright light. REPLACE PCM. REMOVE breakout box. RERUN Quick Test.

Customer: replied 5 years ago.

Thanks Moose!

After reading your answer I'm wondering if it could be just old age and too many miles.

It's got 180,000 on it. It's on it's third timing belt also. It seems to run fine and this only happens occasionally and always when putting around town. Last road trip was 1600 miles round trip (almost all interstate) and never once did the light come on.

 

I've checked for vacuum leaks myself and two dealerships did the same. She's not as zippy as she use to be and the compression ain't what it use to be either.

Expert:  Chris (aka- Moose) replied 5 years ago.

Old age can be a factor. As you can see in the long test. Its not a simple fix or find. Personally I would not bother with it since its so rare in occuring. Since you have checked for vacuum leaks it sure wouldnt hurt to check the fuel pressure. Here is a fuel system tuneup we do often to aid in getting some mpg and performance back.

graphic

Chris (aka- Moose), Ford Technician
Category: Ford
Satisfied Customers: 33406
Experience: 16 years experience with Ford.
Chris (aka- Moose) and 4 other Ford Specialists are ready to help you
Customer: replied 5 years ago.

Thanks!

I'll try the fuel system tune up and recheck the fuel pressure. (dealership said that it was within limits)

 

I'm thinking now that as long as it's only occasionally and It passes state inspections I may just run it till it drops so to speak!

 

Thanks again

Expert:  Chris (aka- Moose) replied 5 years ago.
Your welcome

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