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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