DTC P1131 [YF (2.0L Zetec)]

id0102d0823100

DTC P1131

Lack of HO2S (Front) switch, sensor indicates lean

DETECTION CONDITION

• The PCM monitors HO2S-11 signal switching during over rich condition at PCM terminal 60. If the PCM no longer detects switching for calibrated amount of time, the PCM determines that HO2S-11 cannot switch from lean to rich.

POSSIBLE CAUSE

• Electrical components malfunction
- Water in harness connector
- Open circuit in wiring between HO2S-11 terminal 4 and PCM terminal 60
- Short to GND in wiring between HO2S-11 terminal 4 and PCM terminal 60
- Corrosion or poor mating terminals and wiring
• Fuel system malfunction
- Contaminated in fuel injectors
- Leaking in fuel pressure regulator
- Low fuel pressure or running out of fuel
- Vapor recovery system
• Intake-air system malfunction
- Air leaks after MAF sensor
- Vacuum leaks
- PCV system malfunction
- Improperly seated engine oil dipstick
• EGR system malfunction
- Leaking gasket
- EGR valve stuck
- Vacuum leaking at EGR valve diaphragm or EGR solenoid valve
• Base engine malfunction
- Oil overfill
- Cam timing
- Cylinder compression
- Exhaust leaks before or near HO2S-11

Diagnostic procedure

Warning
• Read the following warnings before performing the fuel system services:
- Fuel vapor is hazardous. It can easily ignite, causing serious injuries and damage. Always keep sparks and flames away from fuel.
- Fuel line spills and leakage are dangerous. Fuel can ignite and cause serious injuries or death and damage. Fuel can also irritate skin and eyes. To prevent this, always complete "BEFORE SERVICE PRECAUTION" and "AFTER SERVICE PRECAUTION" decided in this manual.
Caution
• Disconnecting/connecting quick release connector without cleaning it may possibly cause damage to fuel pipe and quick release connector. Always clean quick release connector joint area before disconnecting/connecting, and make sure that it is free of foreign materials.

STEP

INSPECTION

ACTION

1
VERIFY FREEZE FRAME DATA HAS BEEN RECORDED
• Has FREEZE FRAME DATA been recorded?
Yes
Go to the next step.
No
Record the FREEZE FRAME DATA on the repair order, then go to the next step.
2
VERIFY REPAIR INFORMATION AVAILABILITY
• Verify related service repair information availability.
• Is any related repair information available?
Yes
Perform repair or diagnosis according to the available repair information.
If the vehicle is not repaired, go to the next step.
No
Go to the next step.
3
INDETIFY TRIGGER DTC FOR FREEZE FRAME DATA
• Is DTC P1131 on FREEZE FRAME DATA?
Yes
Go to the next step.
No
Go to FREEZE FRAME DATA DTC inspection.
4
PERFORM VISUAL INSPECTION
Note
• It is necessary to address all Continuous Memory Ignition and Misfire DTCs, if received during Continuous Memory testing, before addressing any Fuel Trim DTCs.
• Check visually for following:
- Intake-air for leaks, obstructions and damage.
- Air cleaner element, air cleaner housing for blockage.
- Integrity of the PCV system
- Vacuum leaks
• Were any concerns found during inspection?
Yes
Repair or replace malfunctioning part, then go to Step 33.
No
Go to the next step.
5
CHECK CONDITIONS RELATED TO MAF SENSOR
Note
• Most weather service reports are a local barometric pressure that has been corrected to sea level. However, the BARO PID reports the actual barometric pressure for altitude the vehicle is being diagnosed in Local weather conditions (high or low pressure areas) will change the local barometric pressure by several inches of mercury [+/- 3 Hz. (+/- 1 in.Hg.)].
• Verify the MAF sensor is connector. If not, repair as necessary.
• Connect the WDS or equivalent to DLC-2.
• Start the engine.
• Access the BARO, LONGFT1 and MAF V PIDs on fully warmed-up engine.
• Check that the BARO PID is approximately the same as the barometric pressure reading for the location, day and altitude the vehicle is being diagnosed at.
- BARO PID values in PCM memory require updating at high throttle openings. If vehicle is driven down from higher altitudes for diagnosing, complete three or four heavy accelerations at greater than half-throttle to allow BARO PID to update.
- BARO PID must be within +/- 6Hz. (+/- 2 in.Hg.) of the altitude value in Barometric Pressure Reference Chart (at Training Manual).
- Make BARO PID comparisons to Barometric Pressure Reference Chart or diary airport barometric pressure reports, if available.
• Check that the LONGFT1 PID at idle is not more negative than -12%.
• Check that the MAF V PID at idle and neutral is not greater then 30% of the normal MAF V listed in Section 01-40, Reference values (or not greater than 1.1 V).
• Are two of the above three check normal?
Yes
Go to Step 7.
No
Go to the next step.
6
CHECK TO ISOLATE MAF SENSOR FROM LEAN DELIVEABILITY OCCURRENCE
Note
• Due to increasingly stringent emission/OBD requirements, a fuel system DTC on some vehicles will be generated without a noticeable drivability concern with or without MAF sensor disconnected. Under these conditions, if the BARO, LONGFT1 and MAF V PID indicates a MAF sensor concern, replace the MAF sensor.
• Disconnect MAF sensor.
• Start the engine.
• Drive the vehicle.
• Is the lean drivability symptom (lack of power, spark knock/detonation, back/jerk or hesitation/surge on acceleration) gone?
Yes
Replace MAF sensor, then go to Step 33.
No
Go to the next step.
7
PERFORM KOER SELF TEST
• Disconnect fuel vapor hose from intake manifold and plug fitting at intake manifold.
• Connect the WDS or equivalent to DLC-2.
• Start the engine and run at 2,000 rpm for 5 minutes and return to idle.
• Complete Key On Engine Running (KOER) self test.
• Are any HO2S DTCs P1131 present?
Yes
Go to the next step.
No
Go to Step 14.
8
HO2S-11 CIRCUIT TEST (WITH LEAN DTCS)
• Disconnect HO2S-11.
• Connect the WDS or equivalent to DLC-2.
• Turn the ignition switch to ON.
• Access O2S11 PID.
Note
• If arcing occurs (including a short), remove jumper wire and go to Step 12 (check fuse in the heater circuit).
• Jumper the HO2S-11 terminal 4 and 1 at the harness side connector.
• Is O2S11 PID reading 1.30 V or greater?
Yes
Inspect for circuit between HO2S-11 terminal 3 and PCM terminal 91.
Then go to the next step.
No
Go to Step 11.
9
CHECK SIGNAL RETURN CIRCUIT FOR OPEN
• Measure resistance between HO2S-11 harness side connector terminal 3 and the battery negative post.
•  Is resistance reading less than 5.0 ohms?
Yes
Go to Step 14.
No
Go to the next step.
10
CHECK HO2S-11 SIGNAL RETURN CIRCUIT FOR OPEN IN HARNESS
• Disconnect PCM.
• Measure resistance between HO2S-11 terminal 3 and PCM terminal 91 at harness side connector.
• Is resistance reading less than 5.0 ohms?
Yes
Replace PCM, then go to Step 33.
No
Replace open circuit, then go to Step 33.
11
CHECK HO2S-11 SIGNAL AND HO2S-11 GND CIRCUIT FOR OPEN IN HARNESS
• Disconnect PCM.
• Measure resistance between HO2S-11 terminal 4 and PCM terminal 60 at harness side connector.
• Is resistance reading less than 5.0 ohms?
Yes
Go to the next step.
No
Replace open circuit, then go to Step 33.
12
CHECK HO2S-11 SIGNAL CIRCUIT FOR SHORT TO GND IN HARNESS
• Disconnect PCM.
• Measure resistance following at PCM harness side connector.
- Between terminal 60 and 24, 51, 76, 103
- Between terminal 60 and 91
• Is each resistance greater than 10,000 ohms?
Yes
Go to the next step.
No
Replace for short to GND circuit, then go to Step 33.
13
CHECK HO2S-11 SIGNAL CIRCUIT FOR SHORT TO GND IN THE SENSOR
• Disconnect PCM.
• Reconnect HO2S-11.
• Measure resistance following at PCM harness side connector.
- Between terminal 60 and 24, 51, 76, 103
- Between terminal 60 and 91
• Is each resistance greater than 10,000 ohms?
Yes
Replace PCM, then go to Step 33.
No
Replace HO2S-11, then go to Step 33.
14
CHECK FUEL PRESSURE
• Install the fuel pressure gauge.
• Connect the WDS or equivalent to DLC-2.
• Turn the ignition switch to ON.
• Turn the fuel pump to on using the PID FP on simulation function.
Note
• The fuel pump will only operate for approximately 8 s when simulation function is selected and activated.
• Is the fuel pressure within with range for the vehicle being diagnosed?
Yes
Go to the next step.
No
Go to Step 26.
15
CHECK INJECTOR FAULT PIDS AND ASSOCIATED DTCS
• Access INJ1F, INJ2F, INJ3F and INJ4F PIDs.
Note
• If misfire DTCs are present, access only injector fault PIDs corresponding to misfire DTCs.
• Is DTC P0201 through P0204 or an injector (s) fault present?
Yes
Go to the next step.
No
Go to Step 19.
16
CHECK FUEL INJECTOR (S) AND HARNESS RESISTANCE
Note
• This causes Continuous Memory DTCs.
• Disconnected PCM.
Note
• Use the fuel injector fault PID to determine the fuel injector circuit (s) requiring testing.
• Measure resistance following for malfunctioning injector in Step 15 at PCM harness side connector.
- Between 70 and 71, 97 (INJ1F, P0201)
- Between 96 and 71, 97 (INJ2F, P0202)
- Between 20 and 71, 97 (INJ3F, P0203)
- Between 95 and 71, 97 (INJ4F, P0204)
• Is the resistance between 11.0-18.0 ohms?
Yes
Replace PCM, then go to Step 33.
No
Go to the next step.
17
CHECK FUEL INJECTOR HARNESS RESISTANCE
• Disconnect the malfunctioning fuel injector in Step 15.
• Measure the resistance for following at harness side connector:
- Between fuel injector No.1 terminal 2 and PCM terminal 71, 97 (INJ1F, P0201)
- Between fuel injector No.1 terminal 1 and PCM terminal 70 (INJ1F, P0201)
- Between fuel injector No.2 terminal 2 and PCM terminal 71, 97 (INJ2F, P0202)
- Between fuel injector No.2 terminal 1 and PCM terminal 96 (INJ2F, P0202)
- Between fuel injector No.3 terminal 2 and PCM terminal 71, 97 (INJ3F, P0203)
- Between fuel injector No.3 terminal 1 and PCM terminal 20 (INJ3F, P0203)
- Between fuel injector No.4 terminal 2 and PCM terminal 71, 97 (INJ4F, P0204)
- Between fuel injector No.4 terminal 1 and PCM terminal 95 (INJ4F, P0204)
• Is each resistance less than 5.0 ohms?
Yes
Go to the next step.
No
Repair for open circuit, then go to Step 33.
18
CHECK FUEL INJECTOR HARNESS CIRCUIT FOR SHORT TO POWER AND GROUND
• Disconnect PCM.
• Malfunctioning fuel injector in Step 15 disconnected.
• Measure resistance for following at PCM harness side connector.
- Terminal 70 and 71, 97 (INJ1F, P0201)
- Terminal 70 and 24, 51, 76, 103 (INJ1F, P0201)
- Terminal 96 and 71, 97 (INJ2F, P0202)
- Terminal 96 and 24, 51, 76, 103 (INJ2F, P0202)
- Terminal 20 and 71, 97 (INJ3F, P0203)
- Terminal 20 and 24, 51, 76, 103 (INJ3F, P0203)
- Terminal 95 and 71, 97 (INJ4F, P0204)
- Terminal 95 and 24, 51, 76, 103 (INJ4F, P0204)
• Is each resistance greater than 10,000 ohms?
Yes
Go to the next step.
No
Repair for short circuit, then go to Step 33.
19
INSPECT FUEL INJECTOR (S)
• Inspect fuel injectors.
• Are fuel injectors normal?
Yes
Go to the next step.
No
Replace suspected fuel injector, then go to Step 33.
20
INSPECT INDUCTION SYSTEM FOR AIR LEAKS
• Inspect the following areas for signs of air leaks:
- Inlet tube (s) from air cleaner to throttle body
- Gaskets which seal the upper and lower intake manifold.
- Vacuum hoses and lines for cranks and proper connections.
- PCV system.
• Are there any signs of leaks or damage?
Yes
Repair or replace malfunctioning part, then go to Step 33.
No
Intermittent malfunction exist, go to the Step 33.
21
CHECK CYLINDER COMPRESSION
• Check cylinder compression at cylinders.
• Are cylinder compression readings within specification?
Yes
Go to the next step.
No
Repair or replace malfunctioning part according inspection results.
Then go to Step 33.
22
CHECK VACUUM OR AIR LEAKS
• Inspect the following:
- Water contamination in connector
- Leaking vacuum actuators
- Engine sealing (Intake manifold and IAC valve)
- EGR system (EGR valve)
- PCV system (PCV valve and hose)
- Unmetered air leaks between throttle body and MAF sensor assembly.
• Are all items normal?
Yes
Go to the next step.
No
Repair or replace malfunctioning part, then go to Step 33.
23
CHECK HO2S-11'S ABILITY TO GENERATE A VOLTAGE GREATER THAN 0.5 V
• Inspect HO2S-11 harness for chafing, burned wires or other damage and repair as necessary.
• Unplug the HO2S-11.
• Connect the digital multimeter to the HO2S-11 terminal 3 and 4 at component side connector.
• Run engine 2,000 rpm for three minutes.
• Rerun the KOER self test and monitor HO2S-11 voltage.
•  Is the voltage greater than 0.5 V during or at the end of self test?
Yes
Go to the next step.
No
Replace HO2S-11, then go to Step 33.
24
MONITOR O2S11 PID FOR PROPER SWITCHING
• Start the engine and run it at idle.
• Warm up the engine to normal operating temperature.
• Access O2S11 PID.
• Wiggle, bend and shake small sections of the emission harness from the PCM and HO2S-11.
• Did the O2S11 PID stay low (less than 0.45 V)?
Yes
Repair isolate area of harness concern causing lack of HO2S-11 switches, then go to Step 33.
No
Go to the next step.
25
TEST DRIVE WHILE MONITORING O2S11 PID FOR SWITCHING
• Access O2S11 PID for proper operation.
• While observer views PID, test drive vehicle under different road conditions in an attempt to simulate the original fault.
• Does O2S11 switch properly?
Yes
Intermittent concern exists, go to Intermittent Troubleshooting Procedure.
No
Replace HO2S-11, then go to Step 33.
26
CHECK SYSTEM INTEGRITY
• Visually inspect the following complete fuel delivery system for damage, leaks, looseness, cracks, kinks, pinching, or abrasion caused by a collision or mishandling:
- Fuel line
- Fuel line connection
- Relays
- Fuel tank
- Fuel pump
- Fuel pressure regulator
- Pulsation damper
- Fuel injector
• Visually inspect electrical harness and connectors for loose pins, corrosion, abrasion, or other damage from collision or mishandling.
• Check electrical connectors for proper mating.
• Verify vehicle has followed maintenance schedule.
• Verify inertia fuel shutoff (IFS) switch is set.
• Verify battery is fully charged (12.5 V or higher).
• Verify electrical/fuse integrity.
• Verify fuel level in the tank is sufficient.
• Are any concerns present?
Yes
Repair or replace malfunctioning part, then go to Step 33.
No
Go to the next step.
27
CHECK VOLTAGE AT FUEL PUMP HARNESS CONNECTOR
• Follow the IFS switch reset procedure.
• Connect battery charger.
• Verify IFS switch state.
• Connect the WDS or equivalent to DLC-2.
• Disconnect the fuel pump harness connector at the fuel pump.
• Turn the ignition switch to ON.
• Access FP PID.
• Connect a digital multimeter between the fuel pump terminal 1 and 3 at fuel pump harness side connector.
• Measure voltage during fuel pump operates using simulation function FP PID.
• Is the voltage greater than 12.5 V?
Yes
Go to the next step.
No
Inspect for following circuit.
• Between fuel pump terminal 1 and IFS switch terminal 2
• Between fuel pump terminal 3 and body GND
• Between IFS switch terminal 1 and fuel pump relay terminal 87
Then go to Step 33.
28
CHECK FUEL FILTER FOR PROPER MAINTENANCE
• Locate and inspect the vehicle maintenance schedule and fuel filter.
• Check for last repair date.
• Was the fuel filter replaced with the last scheduled maintenance interval?
Yes
Go to the next step.
No
Replace fuel filter, then go to Step 33.
29
CHECK FUEL PRESSURE
• Install the fuel pressure gauge.
• Release the fuel pressure.
• Turn the ignition switch to ON.
• Access FP PID.
• Run the fuel pump to obtain maximum fuel pressure using simulation function FP PID.
Note
• The fuel pump will only operate for approximately 8 s when simulation function is selected and activate.
• Is the fuel pressure within the specified pressure range?
Yes
Go to Step 32.
No

Greater than 448 kPa:

Replace fuel pressure regulator in fuel tank, then go to Step 33.

Less than 310 kPa:

Go to the next step.
30
CHECK PRESSURE REGULATOR AND PULSATION DAMPER DIAPHAGM
• Fuel pressure gauge installed.
• Start the engine and run it for 10 s.
• Stop the engine and wait 10 s.
• Start the engine and run it for 10 s.
• Stop the engine and remove the vacuum hose from pulsation damper port.
• Inspect for fuel in the vacuum hose or pulsation damper.
• Is fuel present in the vacuum hose or pulse damper?
Yes
Replace the pulsation damper, then go to Step 33.
No
Go to the next step.
31
CHECK FUEL SUPPLY LINE FOR RESTRICTION
• Disconnect fuel supply line at the fuel rail.
• Disconnect fuel supply line at the fuel pump.
• Check the fuel supply line for restrictions due to blockage, kinking or pinching.
• Apply 21 to 34 kPa regulated shop air pressure to the fuel supply line.
• Does air flow freely through the line?
Yes
Replace the fuel pump unit, then go to Step 33.
No
Repair or replace for fuel line, then go to Step 33.
32
CHECK FUEL INJECTOR
• Perform the FUEL INJECTOR INSPECTION.
• Are fuel injectors normal?
Yes
Intermittent malfunction exist, go to the next step.
No
Replace malfunctioning fuel injector, then go to the next step.
33
VERIFY TROUBLESHOOTING OF DTC P1131 COMPLETED
• Make sure to reconnect all disconnected connectors.
• Clear the DTC from the PCM memory using the WDS or equivalent.
• Perform KOER self test.
• Is the PENDING CODE same DTC present?
Yes
Replace PCM, then go to the next step.
No
Go to the next step.
34
VERIFY AFTER REPAIR PROCEDURE
• Perform "After Repair Procedure".
• Is there any DTC present?
Yes
Go to the applicable DTC inspection.
No
Troubleshooting completed.