Code Po420 Any Sugestions
 

Code P0420 Catalyst Efficiency Below Threshold (bank1) Good Morning Can Any Body Tell Me What Part Needs To Be Replaced I Have A 1996 2.3 Manual Xl Ranger It Turned On Last Night Towing A 500lb Trailer Thanks For Your Imput Much Appreciated! Im A New User And This Web Site Is Great

I Found The Tec Info Wondering What The Most Common Prob When This Code Shows Thanks

HF: Catalyst Efficiency Monitor and Exhaust Systems HF: Introduction

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HF1 DTCs P0420, P0421, P0430 or P0431: CHECK FOR MISFIRE MONITOR DTCS
Diagnostic Trouble Codes (DTC) P0420 and P0421 indicate that bank 1 catalyst system efficiency is below the acceptable threshold.

Diagnostic Trouble Codes (DTC) P0430 and P0431 indicate that bank 2 catalyst system efficiency is below the acceptable threshold.

NOTE 1: Complete the spark timing check in Quick Test before proceeding with this test step. Spark timing retarded below specification may increase exhaust gas temperature and decrease catalyst efficiency over time.

NOTE 2: Be sure customer has not:

Refueled vehicle with leaded gasoline.
Experienced high vehicle oil consumption.
NOTE 3: If entering this Pinpoint Test for symptoms only, go immediately to HF5 .

NOTE 4: Internal deterioration of a catalytic converter is usually caused by abnormal engine operation upstream of the catalyst. Events that may produce higher than normal temperatures in the catalyst are particularly suspect. For example, misfiring can cause higher than normal catalyst operating temperatures.

Possible causes:

Use of leaded fuel.
Oil contamination.
Cylinder misfiring.
Damaged HO2S.
Damaged ECT sensor.
Downstream HO2S wires improperly connected.
Fuel pressure too high.
Damaged exhaust system pipe.
Damaged exhaust manifold.
Damaged muffler/tail-pipe assembly.
Damaged catalytic converter.
Key on, engine off.
Retrieve and record all Continuous Memory DTCs (MIL and non-MIL).
Were any of the following misfire monitor DTCs recorded: P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 and P0308?
Yes No
GO to Section 5A, Powertrain Diagnostic Trouble Code (DTC) Charts , to address the misfire monitor DTCs. GO to HF2 .

HF2 CHECK FOR HO2S MONITOR DTCS
NOTE 1: Incorrect HO2S signal input (e.g. rich/lean input signal when the engine is operating under lean/rich conditions) may cause an abnormal temperature increase in the catalyst.

NOTE 2: Non-California applications will not have an active HO2S monitor. As a result, a Catalyst Efficiency Monitor DTC can be generated for a rear HO2S concern. To check for a rear HO2S concern on these applications, go to the HO2S monitor Pinpoint Test Step H81 . If any repair actions are necessary in Pinpoint Test H , run KOER Self-Test, to verify the repair. If repair actions are not necessary, go to HF3 .

Were any of the following HO2S monitor DTCs recorded in HF1: P0136, P0138, P0140 and P0141 (Bank 1, rear HO2S) or P0156, P0158, P0160 and P0161 (Bank 2, rear HO2S)?
Yes No
GO to Section 5A, Powertrain Diagnostic Trouble Code (DTC) Charts , to address the HO2S Monitor DTCs. GO to HF3 .

HF3 CHECK FOR ECT SENSOR DTCS

Note: ECT sensor DTCs can be an indication that the thermostat is not operating correctly or that the coolant level is not filled to specifications, producing above normal operating temperatures.

Were any of the following ECT sensor DTCs recorded in HF1: P0117, P0118, P0125 and P1117?
Yes No
GO to Section 5A, Powertrain Diagnostic Trouble Code (DTC) Charts , to address the ECT sensor DTCs. GO to HF4 .

HF4 CHECK FOR ANY OTHER DTCS
Were any other DTCs recorded in HF1 (not including the initial P0420/P0421 or P0430/P0431 DTCs)?
Yes No
GO to Section 5A, Powertrain Diagnostic Trouble Code (DTC) Charts , to address the DTCs. GO to HF5 .

HF5 CHECK REAR HO2S WIRING

Note: If the electrical connections of the rear HO2S are interchanged/crossed, the Catalyst Efficiency Monitor Test will be failed.

Inspect the wiring of each rear HO2S for proper routing and connection.
Are the HO2S wires improperly routed?
Yes No
Correctly route/connect the rear HO2S harness circuit(s). COMPLETE the PCM Reset to clear all DTCs (REFER to Section 2A, Powertrain Control Module (PCM) Reset ). RERUN Quick Test . No EEC-V root causes related to the DTCs or symptoms. GO to HF6 .

HF6 CHECK FUEL PRESSURE
WARNING: THE FUEL SYSTEM WILL REMAIN PRESSURIZED WHEN THE ENGINE IS NOT RUNNING. TO PREVENT INJURY OR FIRE, USE CAUTION WHEN WORKING ON THE FUEL SYSTEM.

Note: Fuel pressures above specification may produce an abnormally rich air/fuel mixture. The rich air/fuel mixture may cause higher than normal catalyst operating temperatures.

Key off.
Inspect the vacuum hose going to the fuel pressure regulator for proper installation, cracks, etc. Service as necessary.
Install fuel pressure gauge.
Verify vacuum source to fuel pressure regulator.
Start and run the engine at idle. Record the fuel pressure.
Increase engine speed to 2500 rpm and maintain for one minute. Record the fuel pressure.
Is the fuel pressure between 30 and 40 psi (210-310 kPa)?
Yes No
Fuel pressure is OK. REMOVE the fuel pressure gauge. GO to HF7 . Fuel pressure is out of specification.

For Probe:

REFER to Probe Fuel Delivery System Section B, for diagnosis.

All others:

REFER to Pinpoint Test Step HC1 , Fuel Delivery Systems, for diagnosis. COMPLETE PCM Reset to clear DTCs (REFER to Section 2A, Powertrain Control Module (PCM) Reset ). RERUN Quick Test .






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HF7 CHECK FOR OBVIOUS LEAK SOURCES IN THE EXHAUST SYSTEM
Note: If a catalyst is in series with a leaking exhaust system, it can fail the Catalyst Efficiency Monitor test.

Key off.
Inspect the following for leaks, cracks, loose connections or punctures:
Exhaust manifold.
Front exhaust pipe.
Rear exhaust pipe.
Muffler/tail-pipe assembly.
Are the above components free of cracks and punctures, etc.?
Yes No
CHECK that the exhaust manifold to catalyst inlet pipe joint is tight. GO to HF8 . REPLACE/REPAIR the leak source(s). COMPLETE PCM Reset to clear DTCs (REFER to Section 2A, Powertrain Control Module (PCM) Reset ). RERUN Quick Test .

HF8 CHECK FOR OBVIOUS RESTRICTIONS IN THE EXHAUST SYSTEM
Inspect the following for dents, areas of collapsed material and unusual bending:
Front exhaust pipe.
Rear exhaust pipe.
Muffler/tail-pipe assembly.
Are the components free of dents and areas of collapsed material or unusual bending, etc.?
Yes No
GO to HF9 . REPLACE/REPAIR the restricted component(s) as necessary. COMPLETE PCM Reset to clear DTCs (REFER to Section 2A, Powertrain Control Module (PCM) Reset ). RERUN Quick Test .

HF9 CHECK MANIFOLD VACUUM FOR INDICATION OF EXCESSIVE EXHAUST SYSTEM RESTRICTION
Attach a vacuum gauge to the intake manifold vacuum source.
Install a tachometer.
Observe the vacuum gauge needle while performing the following:
Note: The vacuum gauge reading may be normal when the engine is first started and idled. However, excessive restriction in the exhaust system will cause the vacuum gauge needle to drop to a low point even while the engine is idled.

Start the engine and gradually increase the rpm to 2000 with the transmission in NEUTRAL.
Decrease engine speed to base idle rpm.
Key off.
Did manifold vacuum rise above 16 inches Hg with the engine rpm at 2000?
Yes No
GO to HF10 . Manifold vacuum did not reach an acceptable level. An excessive restriction may be present. GO to HF11 .

HF10 CHECK MANIFOLD VACUUM FOR INDICATION OF MODERATE EXHAUST SYSTEM RESTRICTION
Vacuum gauge installed.
Tachometer installed.
Key on, engine idling.
Increase the engine speed gradually from base idle rpm to 2000 rpm with the transmission in NEUTRAL.
Observe the speed the vacuum gauge needle rises, while maintaining the increased engine rpm.
Note: 1: On a non-restricted exhaust system, the vacuum gauge needle will rise quickly to the normal range as the increased rpm is maintained.

Note: 2: On a restricted exhaust system, the vacuum gauge needle will rise slowly to the normal range as the increased rpm is maintained.

Note: 3: The rate of speed the vacuum gauge needle rises to the normal range is slower on a restricted system than on a non-restricted system as the increased rpm is maintained.

Decrease engine speed to base idle rpm.
Key off.
Is the rate of speed that the vacuum gauge needle rises back to the normal range (above 16 inches Hg) much slower than that of a non-restricted system?
Yes No
A moderate restriction may be present. GO to HF11 . No indications of restrictions or leaks have been detected in the exhaust system. If here because of DTCs P0420/P0421 or P0430/P0431, the catalytic converter is chemically inactive. REPLACE the catalytic converter, being careful to avoid improper routing of the rear HO2S. COMPLETE PCM Reset to clear DTCs (REFER to Section 2A, Powertrain Control Module (PCM) Reset ). RERUN Quick Test . REMOVE the vacuum gauge and tachometer. For further diagnosis of symptom (e.g. Lack of Power, Loss of Power, or No Start) REFER to Section 4A, Symptom Flowcharts.

HF11 CHECK MANIFOLD VACUUM WITH EXHAUST MANIFOLD DISCONNECTED FOR INDICATION OF A RESTRICTION
Key off.
Disconnect exhaust system immediately after the exhaust manifold.
Repeat the vacuum measurement found in test step HF10 .
Did the vacuum needle QUICKLY rise above 16 inches Hg with the engine rpm at 2000?
Note: An intake manifold gasket leak can also cause the vacuum gauge needle to remain well below the normal range.

Yes No
The exhaust system restriction is downstream of the exhaust manifold. RECONNECT exhaust system at exhaust manifold. GO to HF12 . A restriction is present in the exhaust manifold. REMOVE the vacuum gauge and tachometer. INSPECT each exhaust port for casting flash/restrictions by dropping a length of chain into it (NOTE: Do not use a wire or lamp to check the ports. The restriction may be large enough for both to pass through, but small enough to cause excessive back pressure at high engine rpm.). REPLACE the exhaust manifold if unable to remove the casting flash/restriction. COMPLETE PCM Reset to clear DTCs (REFER to Section 2A, Powertrain Control Module (PCM) Reset ). RERUN Quick Test .

HF12 CHECK MANIFOLD VACUUM WITH MUFFLER/TAIL-PIPE ASSEMBLY DISCONNECTED FOR INDICATION OF A RESTRICTION
Key off.
Disconnect muffler/tail-pipe assembly located after the catalytic converter.
Repeat the vacuum measurement found in test step HF10 .
Did the vacuum needle QUICKLY rise above 16 inches Hg with the engine rpm at 2000?
Yes No
There is a restriction in the muffler/tail-pipe assembly. REPLACE the muffler/tail-pipe assembly. REMOVE the vacuum gauge and tachometer. COMPLETE PCM Reset to clear DTCs (REFER to Section 2A, Powertrain Control Module (PCM) Reset ). RERUN Quick Test . There is a restriction in the catalytic converter. REMOVE the vacuum gauge and tachometer. REPLACE the catalytic converter, being careful to avoid improper routing of the rear HO2S and INSPECT the muffler to be certain converter debris has not entered. RECONNECT muffler/tail-pipe assembly. COMPLETE PCM Reset to clear DTCs (REFER to Section 2A, Powertrain Control Module (PCM) Reset ). RERUN Quick Test .

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