Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Manual - part 1295

6E1–256

RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

DTC P0406  EGR Sensor Circuit High

  (Cont'd)

Step

No

Yes

Value(s)

Action

14

Replace the Linear Exhaust Gas Recirculation (EGR)
Valve.
Verify Repair.

—

—

—

15

Replace the PCM.

IMPORTANT: The replacement PCM must be
programmed. Refer  to On–Vehicle Service in
Powertrain Control Module and Sensors for
procedures. 

And also refer to latest Service Bulletin.
Check to see if the Latest software is released or not.
And then Down Load the LATEST PROGRAMMED
SOFTWARE to the replacement PCM.

Verify repair.

—

—

—

6E1–257

RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

DIAGNOSTIC TROUBLE CODE (DTC) P0420  CATALYST SYSTEM EFFICIENCY

BELOW THRESHOLD

060R100032

Circuit Description

The PCM uses the Bank 1 HO2S 1 and the Bank 1 HO2S
2 heated oxygen sensors. The Bank 1 HO2S 1 sensor
produces an output signal which indicates the amount of
oxygen present in the exhaust gas entering the
three–way catalytic converter. The Bank 1 HO2S 2
sensor produces an output signal which indicates the
oxygen storage capacity of the catalyst; this in turn
indicates the catalyst’s ability to convert exhaust gases
efficiently. If the catalyst is operating efficiently, the Bank
1 HO2S 1 signal will be far more active than that produced
by the Bank 1 HO2S 2 sensor. If the PCM detects a level
of Bank 1 HO2S 2 activity that indicates the catalyst is no
longer operating efficiently, Diagnostic Trouble Code
P0420 will be set.  DTC P0420 is a type A code.

Conditions for Setting the DTC

D

No related Diagnostic Trouble Codes.

D

The engine is operating in ”Closed Loop”.

D

Engine coolant temperature is more than 70

°

C and

less than 120

°

C (158

°

F).

D

Calculated air flow is between 2.5 g/second and 7
g/second.

D

Vehicle speed is less than 3 km/h (3 mph).

D

Catalyst temperature is more than 450

°

C and less than

950

°

C.

D

Airflow reset time more than 8 sec or equal to 8 sec.

D

Airflow to reset is equal to 9g/s.

D

Absolute pressure more than 72 kpa.

D

IAT is more than –10

°

C and less than 70

°

C.

D

Engine run time is more than 360 sec.

D

TPS is less than 3%.

D

Idle time less than 60 sec.

D

Oxygen capacity (OSC) time is less than 1.5 sec or
equal to 1.5 sec.

One pass fail decision per key on unless a step change is
OSC time occurs.

Action Taken When the DTC Sets

D

The PCM will illuminate the malfunction indicator lamp
(MIL) the first time the fault is detected.

D

The PCM will store conditions which were present
when the Diagnostic Trouble Code was set as Freeze
Frame and in the Failure Records data.

Conditions for Clearing the MIL/DTC

D

The PCM will turn the MIL OFF on the third consecutive
trip cycle during which the diagnostic has been run and
the fault condition is no longer present.

D

A history Diagnostic Trouble Code P0420 will clear
after 40 consecutive warm–up cycles have occurred
without a fault.

D

Diagnostic Trouble Code P0420 can be cleared by
using the Scan Tool’s ”Clear Info” function.

6E1–258

RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

Diagnostic Aids

Check for the following conditions:

D

Poor connection at PCM – Inspect harness connectors
for backed–out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal–to–wire connection.

D

Damaged harness – Inspect the wiring harness for
damage; shorts to ground, shorts to battery positive
and open circuits. If the harness appears to be OK,
observe the display on the Tech 2 while moving
connectors and wiring harnesses related to the sensor.
A change in the display will indicate the location of the
fault.

Reviewing the Failure Records vehicle mileage since the
diagnostic test last failed may help determine how often
the condition that caused the Diagnostic Trouble Code to
be set occurs. This may assist in diagnosing the
condition.

D

Bank 1 HO2S 1/Bank 1 HO2S 2 Activity Test:
Ensure that the engine is fully warmed up.

Using a Tech 2, monitor Bank 1 HO2S 1 and Bank 1
HO2S 2 displays in ”Neutral” while using the Tech 2
IAC RPM control function to maintain a mass air flow
of 10 g/second. Compare the amount of activity
(frequency and amplitude) on Bank 1 HO2S 1 to the
activity on Bank 1 HO2S 2 over a 30 second period.

If the amount of activity on Bank 1 HO2S 2 is nearly as
great as the activity on Bank 1 HO2S 1, a problem exists.
Use the Diagnostic Trouble Code P0420 diagnostic chart.
If much less activity is noted on Bank 1 HO2S 2, the
system is functioning properly.
The ”TWC Monitor Test Counter” displayed on the Tech 2
may be used to monitor the progress of the TWC
diagnostic. To complete the TWC diagnostic with a good
catalyst, the counter must be allowed to increment to 49
samples and roll over to 0 at least twice. A failed catalyst
will require three or more 50–sample tests to report a
failure.

Test Description

Number(s) below refer to the step number(s) on the
Diagnostic Chart:
7. Difficulty completing the Diagnostic Trouble Code

P0420 ”Status This Ign.” test may be encountered in
areas where test conditions cannot be maintained
easily, especially in urban areas. To minimize the
amount of driving required to complete the
Diagnostic Trouble Code P0420 ”Status This Ign.”
test, use the following procedure:

D

Allow the engine to warm completely.

D

With the vehicle in ”Neutral,” monitor the calculated
air flow on the Tech 2 and hold part throttle to
maintain a reading of over 12 g/second for at least 2
minutes. This will achieve the ”warm catalyst”
required for running the test.

D

Operate the vehicle in second or third gear to remain
in the Diagnostic Trouble Code P0420 test
conditions described in ”Conditions for Setting the
Diagnostic Trouble Code” as much as possible. If
you must stop the vehicle, maintain the ”warm
catalyst” criteria as follows:
– Place the vehicle in ”Neutral.”
– Hold part throttle to maintain a calculated air flow

reading of over 15 g/second for the duration of the
stop.

The ”TWC Monitor Test Counter” displayed on the Tech 2
may be used to monitor the progress of the TWC
diagnostic. To complete the TWC diagnostic with a good
catalyst, the counter must be allowed to increment to 49
samples and roll over to 0 at least twice.

6E1–259

RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

DTC P0420 – Catalyst System Efficiency Below Threshold

 

Step

Action

Value(s)

Yes

No

1

Was the ”On–Board Diagnostic (OBD) System Check”
performed?

—

Go to Step  2 

Go to OBD

System

Check 

2

Are any other O2 Sensor Diagnostic Trouble Codes
set?

—

Diagnose

other

Diagnostic

Trouble

Code(s) first

Go to Step  3 

3

1. Visually and physically inspect the three–way

catalytic converter for damage. Check for the
following:

D

dents

D

severe discoloration caused by excessive
temperatures

D

holes

D

internal rattle caused by damaged catalyst

2. Also, ensure that the three–way catalytic converter

is a proper original equipment manufacturer part.

Did your inspection reveal a problem?

—

Go to Step  6 

Go to Step  4 

4

1. Visually and physically inspect the exhaust system

between the three–way catalytic converter and the
rear converter flange for leaks, damage, and loose
or missing hardware.

2. If a problem is found, repair as necessary.

Did your inspection reveal a problem?

—

Go to Step 7

to verify

repair

Go to Step  5 

5

1. Visually and physically inspect the Bank 1  HO2S 2.
2. Ensure that the Bank 1 HO2S 2 is secure and that

the pigtail and wiring harness is not contacting the
exhaust pipe or is not other wise damaged.

3. If a problem is found, repair as necessary.

Did your inspection reveal a problem?

—

Go to Step 7

to verify

repair

Go to Step  6 

6

Replace the three–way catalytic converter.

NOTE: Check for conditions which may cause catalyst
damage (refer to Diagnostic Aids). 

Is the action complete?

—

Go to Step 7

to verify

repair

—

7

1. Review and record the Tech 2 Failure Records data.
2. Clear Diagnostic Trouble Code P0420.
3. Start the engine and allow it to warm up until the

engine coolant temperature monitored on the Tech
2 is above the specified value.

4. Run the engine to maintain the specified mass air

flow range for at least 2 minutes.

5. Operate the vehicle to maintain Diagnostic Trouble

Code P0420 test conditions (for detailed
instructions, refer to Diagnostic Trouble Code Test
Description in Diagnostic Support). 

6. Using a Tech 2, monitor “Diagnostic Trouble Code”

info for DTC P0420 until the DTC P0420 test runs.

7. Note the test result.

Does the Tech 2 indicate DTC P0420 passed this
ignition?

Engine

coolant temp:

greater than

60

°

C (140

°

F)

Calculated air
flow: between

7 g/second

and 41

g/second

Verify repair

Go to

Diagnostic

Aids