HF: Catalyst Efficiency Monitor and Exhaust Systems
HF: Introduction See: HF: Catalyst Efficiency Monitor and Exhaust Systems - Introduction
HF1 DTCs P0420 OR P0430: CHECK FOR MISFIRE DETECTION MONITOR DTCS
NOTE 1: Be sure customer has not:
- Refueled vehicle with leaded gasoline.
- Noticed high vehicle oil consumption.
NOTE 2: If entering this Pinpoint Test for symptoms only, immediately GO to HF5.
NOTE 3: Internal deterioration of a catalytic converter is usually caused by abnormal engine operation upstream of the catalyst. Events that can produce higher than normal temperatures in the catalyst are particularly suspect. For example, misfiring can cause higher than normal catalyst operating temperatures.
- Retrieve and record all Continuous Memory DTCs (MIL and non-MIL).
Were any of the following Misfire Detection Monitor DTCs recorded: P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0309 and P0310?
Yes
to address the Misfire Detection Monitor DTCs.
No
.
HF2 CHECK FOR HO2S MONITOR DTCS
NOTE: Incorrect HO2S signal input (such as rich/lean input signal when the engine is operating under lean/rich conditions) can cause an abnormal temperature increase in the catalyst.
Were any of the following HO2S monitor DTCs recorded in HF1: P0136, P0138 and P0141 (Bank 1, rear HO2S) or P0156, P0158 and P0161 (Bank 2, rear HO2S)?
Yes
to address the HO2S Monitor DTCs.
No
.
HF3 CHECK FOR ECT OR CHT SENSOR DTCS
Note: ECT or CHT sensor DTCs can indicate that the thermostat is not operating correctly or that the engine coolant level is not filled to specification, producing above normal operating temperatures.
Were any of the following ECT or CHT sensor DTCs recorded in HF1: P0117, P0118, P0125, P1117, P1285, P1288, P1289, P1290 and P1299?
Yes
to address the ECT or CHT sensor DTCs.
No
.
HF4 CHECK FOR ANY OTHER DTCS
Were any other DTCs recorded in HF1 (not including the initial P0420 or P0430 DTCs)?
Yes
to address the DTCs.
No
.
HF5 CHECK REAR HO2S WIRING AND PCM CONNECTIONS
Note: If the electrical connections of the rear HO2S are interchanged/crossed, the Catalyst Efficiency Monitor Test will fail.
- Inspect the wiring of each rear HO2S for proper routing and connection.
- Disconnect the PCM, inspect for damaged or pushed out pins, corrosion and loose wires.
Are there any concerns with the HO2S wiring or the PCM connection?
Yes
- REPAIR any wiring or connection concerns. For PCM pin concerns,
REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) See: Programming and Relearning\Flash Electrically Eraseable Programmable Read Only Memory - Flash EEPROM).
COMPLETE Catalyst Monitor OBD II Drive Cycle to verify repair (Refer to Section
2, Drive Cycles See: SECTION 2: Diagnostic Methods\Drive Cycles).
No
- No Electronic EC 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 can produce an abnormally rich air/fuel mixture. The rich air/fuel mixture can cause higher than normal catalyst operating temperatures.
- RETURN FUEL SYSTEM
- Inspect the vacuum hose going to the fuel pressure regulator for proper installation and cracks. Repair as necessary.
- Verify vacuum source to fuel pressure regulator.
- MECHANICAL RETURNLESS FUEL SYSTEM
- If applicable, inspect the vacuum hose going to the fuel rail pulse damper for proper installation and cracks. Repair as necessary.
- Install fuel pressure gauge. NOTE: On Electronic Returnless Fuel System, the fuel pressure can be monitored by scan tool using the Fuel Rail Pressure (FRP) sensor PID.
- 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. GO to Pinpoint Test HC See: HC: Fuel Delivery System - Introduction and compare fuel pressure to the Fuel Pressure Delivery System Test Information Chart at the beginning of the pinpoint.
- Key off.
Was the fuel pressure within specifications?
Yes
gauge. GO to HF7
.
No
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.
- Inspect the following for leaks, cracks, loose connections or punctures:
- Exhaust manifold.
- Front exhaust pipe.
- Rear exhaust pipe.
- Muffler/tailpipe assembly.
Are the above components free of cracks and punctures, etc.?
Yes
.
No
- REPAIR the leak source(s). COMPLETE Catalyst Monitor OBD II
Drive Cycle to verify repair (Refer to Section 2, Drive Cycles See: SECTION 2: Diagnostic Methods\Drive Cycles).
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/tailpipe assembly.
Are the components free of dents and areas of collapsed material or unusual bending, etc.?
Yes
.
No
- REPAIR the restricted component(s) as necessary. COMPLETE Catalyst
Monitor OBD II Drive Cycle to verify repair (Refer to Section 2, Drive Cycles See: SECTION 2: Diagnostic Methods\Drive Cycles).
HF9 CHECK MANIFOLD VACUUM FOR INDICATION OF EXCESSIVE EXHAUST SYSTEM RESTRICTION
- Attach a vacuum gauge to the intake manifold vacuum source.
- Monitor RPM with scan tool or tachometer.
- Observe the vacuum gauge needle while completing the following:
Note: The vacuum gauge reading may be normal when the engine is first started and idling. However, excessive restriction in the exhaust system will cause intake manifold vacuum to decrease with the engine at a steady/constant idle speed.
- Start the engine and gradually increase the engine speed to 2000 rpm with the transmission in NEUTRAL.
- Decrease engine speed to base idle rpm.
- Key off.
Did manifold vacuum rise above 54 kPa (16 inches-Hg) with the engine speed at 2000 rpm?
Yes
.
No
- Manifold vacuum did not reach an acceptable level. GO to HF11
to check for excessive restriction in the exhaust system.
HF10 CHECK MANIFOLD VACUUM FOR INDICATION OF MODERATE EXHAUST SYSTEM RESTRICTION
- 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 54 kPa (16 inches-Hg)) much slower than that of a non-restricted system?
Yes
- A moderate restriction may be present. GO to HF11
.
No
- No indications of restrictions or leaks have been detected in
the exhaust system. If here because of DTCs P0420 or P0430, the catalytic
converter is chemically inactive. REPLACE the catalyst that is located between
the monitored H02S Sensors, only for the bank referenced, (P0420 Bank 1),
(P0430 Bank 2). Do not replace any unmonitored catalyst unless it is serviced
as an assembly. COMPLETE Catalyst Monitor OBD II Drive Cycle to verify repair
(Refer to Section 2, Drive Cycles See: SECTION 2: Diagnostic Methods\Drive Cycles).
For further diagnosis of symptom (e.g. Lack of Power, Loss of Power, or No
Start) REFER to Section 3, Symptom Charts. See: Symptom Related Diagnostic Procedures
HF11 CHECK MANIFOLD VACUUM WITH EXHAUST MANIFOLD DISCONNECTED FOR INDICATION OF A RESTRICTION
Note: An intake manifold gasket leak can also cause the vacuum gauge needle to remain well below the normal range.
- Disconnect exhaust system immediately after the exhaust manifold.
- GO to HF10 and repeat the vacuum measurement.
Did the vacuum needle QUICKLY rise above 54 kPa (16 inches-Hg) with the engine speed at 2000 rpm?
Yes
- The exhaust system restriction is downstream of the exhaust
manifold. RECONNECT exhaust system at exhaust manifold. GO to HF12
.
No
- A restriction is present in the exhaust manifold. 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
can be small enough for both to pass through, but large enough to cause excessive
back-pressure at high engine rpm.). REPLACE the exhaust manifold if unable
to remove the casting flash/restriction. COMPLETE Catalyst Monitor OBD II
Drive Cycle to verify repair (Refer to Section 2, Drive Cycles See: SECTION 2: Diagnostic Methods\Drive Cycles).
HF12 CHECK MANIFOLD VACUUM WITH MUFFLER/TAILPIPE ASSEMBLY DISCONNECTED FOR INDICATION OF A RESTRICTION
- Disconnect muffler/tailpipe assembly from the catalytic converter.
- GO to HF10 to repeat the vacuum measurement.
Did the vacuum needle QUICKLY rise above 54 kPa (16 inches-Hg) with the engine speed at 2000 rpm?
Yes
- There is a restriction in the muffler/tailpipe assembly. REPLACE
the muffler/tailpipe assembly. COMPLETE Catalyst Monitor OBD II Drive Cycle
to verify repair (Refer to Section 2, Drive Cycles See: SECTION 2: Diagnostic Methods\Drive Cycles).
No
catalytic converter. NOTE: On vehicle applications where their is more than
one catalyst, REPLACE only the damaged catalyst assembly. INSPECT the muffler
to be certain converter debris has not entered. COMPLETE Catalyst Monitor
OBD II Drive Cycle to verify repair (Refer to Section 2, Drive Cycles See: SECTION 2: Diagnostic Methods\Drive Cycles).
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