Daewoo Matiz (2003 year). Manual

1F – 208 ENGINE CONTROLS

DIAGNOSTIC TROUBLE CODE (DTC) – P0420 CATALYST LOW EFFICIENCY

Circuit Description

In order to control exhaust emissions of Hydrocarbons
(HC), Carbon Monoxide (CO) and Nitrogen Oxide
(NOx), a Three-Way Catalytic Converter (TWC) is used.
The catalyst within the converter promotes a chemical
reaction which oxidizes the HC and CO present in the
exhaust gas, converting them into harmless water vapor
and carbon dioxide, it also reduces NOx, converting it
into nitrogen. The catalytic converter also has the ability
to store oxygen. The Engine Control Module (ECM) has
the capability to monitor this process using a Heated

Oxygen Sensor (HO2S) located in the exhaust stream
past the TWC. The HO2S produces an output signal
which indicates the oxygen storage capacity of the cata-
lyst; this in turn indicates the catalyst’s ability to convert
exhaust emissions effectively. The ECM monitors the
catalyst efficiency by first allowing the catalyst to heat
up, waiting for a stabilization period while the engine is
idling, and then adding and removing fuel while monitor-
ing the reaction of the HO2S. When the catalyst is func-
tioning properly, the HO2S response to the extra fuel is
slow compared to the Oxygen Sensor (O2S). When the
HO2S response is close to that of the O2S, the Oxygen
storage capability or efficiency of the catalyst is consid-
ered to be bad, and the Malfunction Indicator Lamp
(MIL) will illuminate.

Conditions for Setting the DTC

Oxygen Sensor Capacity test condition:

Closed loop stoichiometry.

Engine is running more than 300 seconds.

Airflow is between 25~50kg/h.

Engine Coolant Temperature (ECT) is more than
70

C(176

F) .

Engine speed between 2,400rpm and 3,000rpm.

Vehicle speed is between 64km/h(28.6mph) and
80km/h(49.7mph).

Note: Test is aborted for this idle if:

Change in engine speed is greater than 80 rpm.

A/C status changed.

Cooling fan status changed.

Insufficient air/fuel shift.

DTC(s) P0106, P0107, P0108, P0117, P0118,
P0122, P0123, P0125, P0131, P0132, P0133,
P1133, P0134, P1134, P0137, P0138, P0140,
P0141, P1167, P1171, P0171, P0172, P0201,
P0202, P0203, P0204, P0300, P0336, P0337,
P0341, P0342, P0351, P0352, P0402, P0404,
P0405, P0406, P0506, P0507, and P0562 are NOT
SET.

Action Taken When the DTC Sets

The Malfunction Indicator Lamp (MIL) will illuminate.

The ECM will record operating conditions at the time
the diagnostic fails. This information will be stored in
the Freeze Frame and Failure Records buffers.

A history DTC is stored.

Conditions for Clearing the MIL/DTC

The MIL will turn off after four consecutive ignition
cycles in which the diagnostic runs without a fault.

A history DTC will clear after 40 consecutive warm-up
cycles without a fault.

DTC(s) can be cleared by using the scan tool.

Diagnostic Aids

The catalyst test may abort due to a change in the en-
gine load. Do not change the engine load (i.e. A/C, cool-
ant fan, heater motor) while a catalyst test is in progress.

An intermittent problem may be caused by a poor con-
nection, rubbed-through wire insulation, or a wire that is
broken inside the insulation.

Any circuitry, that is suspected as causing the intermit-
tent complaint, should be thoroughly checked for the fol-
lowing conditions:

Backed-out terminals

Improper mating

Broken locks

Improperly formed

Damaged terminals

Poor terminal-to-wire connection.

ENGINE CONTROLS 1F – 209

DTC P0420 – Catalyst Low Efficiency

Step

Action

Value(s)

Yes

Perform an Euro On-Board Diagnostic (EOBD)
System Check.
Was the check performed?

–

Go to Step 2

Go to

“On-Board
Diagnostic

System Check”

1. Install a scan tool to the Data link Connector

(DLC).

2. Turn the ignition ON.
Are any component Diagnostic Trouble Codes
(DTCs) set?

–

Go to

Applicable DTC

table

Go to Step 3

1. Visually/physically check the following:
2. Exhaust system for a leak.
3. Heated Oxygen Sensor (HO2S).
Is a problem found?

–

Go to Step 4

Go to Step 5

Repair the exhaust system as needed.
Is the repair complete?

–

Go to Step 6

–

Replace the Three Way Catalytic Converter (TWC).
Is the repair complete?

–

Go to Step 6

–

1. Using the scan tool, clear the Diagnostic Trouble

Codes (DTCs).

2. Start the engine and idle at normal operating

temperature.

3. Operate the vehicle within the Conditions for

setting this DTC as specified in the supporting
text.

Does the scan tool indicate that this diagnostic has
run and passed?

–

Go to Step 7

Go to Step 2

Check if any additional DTCs are set.
Are any DTCs displayed that have not been
diagnosed?

–

Go to

Applicable DTC

table

System OK

Daewoo Matiz (2003 year). Manual - part 74