coolant temperature DAEWOO MATIZ 2003 Service Service Manual

ENGINE CONTROLS 1F–189
DAEWOO M-150 BL2
repairs, the valve warms and the problem disappears.
By watching the Actual EEGR and desired EEGR posi-
tions on a cold vehicle with a scan tool, the fault can beeasily verified. Check the Freeze Frame data to deter-
mine if the DTC set when the vehicle was cold by view-
ing the Engine Coolant Temperature (ECT).
DTC P1403 – Electric Exhaust Gas Recirculation Valve Failure
StepActionValue(s)YesNo
1
Perform an Euro On-Board Diagnostic (EOBD)
System Check.
Is the system check complete?
–
Go to Step 2
Go to
“On-Board
Diagnostic
System Check”
2
1. Turn the ignition switch to with the engine OFF.
2. Install the scan tool.
3. Command the electric exhaust gas recirculation
(EEGR) valve to the specified values.
Does the Actual EEGR Position follow the desired
EEGR position?
25%, 50%,
75%, 100%
Go to Step 19Go to Step 3
3
1. Turn the ignition switch to ON.
2. Disconnect the EEGR valve electrical connector.
3. With a test light connected to B+, probe the
ground circuit to the EEGR valve.
Does the test light illuminate?
–
Go to Step 4Go to Step 5
4
1. Connect the test light to ground.
2. Probe the EEGR control circuit at terminal 1 to
the EEGR valve.
3. Command the EEGR valve to the specified
values using a scan tool.
After the command is raised, does the test light glow
brighter, flash or maintain a steady glow?
25%, 50%,
75%, 100%
Go to Step 6Go to Step 7
5
Repair the open or poor connection in the EEGR
ground circuit.
Is the repair complete?
–
Go to Step 19
–
6
With a test light still connected to ground, probe the
signal circuit at terminal 1.
Does the test light illuminate?
–
Go to Step 8Go to Step 9
7
With a test light still connected to ground, again
probe the signal circuit without commanding the
EEGR valve with the scan tool.
Does the test light illuminate?
–
Go to Step 10Go to Step 11
8
Check the signal circuit for a short to voltage and
repair as necessary.
Is a repair necessary?
–
Go to Step 19Go to Step 12
9
With a digital voltmeter (DVM) connected to ground,
probe the 5V reference circuit at terminal 3.
Is the voltage measured near the specified value?
5VGo to Step 13Go to Step 14
10
Check the control circuit for a short to battery
voltage and repair as necessary.
Is a repair necessary?
–
Go to Step 19Go to Step 12
11
Connect the test light to B+ and again probe the
control circuit at terminal 4.
Does the test light illuminate?
–
Go to Step 15Go to Step 16
12Replace the engine control module (ECM).
Is the replacement complete?–Go to Step 19–

1F–192 ENGINE CONTROLS
DAEWOO M-150 BL2
MAA1F230
DIAGNOSTIC TROUBLE CODE (DTC) – P0404 ELECTRIC EXHAUST GAS
RECIRCULATION OPENED
Circuit Description
An Electric Exhaust Gas Re-circulation (EEGR) system
is used to lower oxides of nitrogen (NOX) emission lev-
els caused by high combustion temperatures. It a ac-
complishes this by feeding small amounts of exhaust
gases back into the combustion chamber. When the air/
fuel mixture is diluted with the exhaust gases, combus-
tion temperatures are reduced.
A linear EEGR valve is used on this system. The linear
EEGR valve is designed to accurately supply exhaust
gases to the engine without the use of intake manifold
vacuum. The valve controls exhaust flow going into the
intake manifold from the exhaust manifold fhrough an
orifice with a engine control module(ECM) controlled
pintle. The ECM controls the pintle position using inputs
from the Throttle Position (TP) and the Manifold Abso-
lute Pressure (MAP) sensor. The ECM then commands
the EEGR valve to operate when necessary by control-
ling an ignition signal through the ECM. This can be
monitored on a scan tool as the Desired EEGR position.
The ECM monitors the results of its command through a
feedback signal. By sending a 5 volt reference and a
ground to the EEGR valve, a voltage signal representing
the EEGR valve pintle position is sent to the ECM. This
feedback signal can also be monitored on a scan tool
and is the actual position of the EEGR pintle. The actual
EEGR position should always be near the commanded
or Desired EEGR position.
ThisDiagnostic Trouble Code(DTC) will detect an open
or short circuit.Conditions for Setting THE DTC

EEGR circuit low voltage.
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.

EEGR is disabled.
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
Due to moisture associated with exhaust systems, the
EEGR valve may freeze and stick in cold weather at
times. After the vehicle is brought into a warm shop for
repairs, the valve warms and the problem disappears.
By watching the Actual EEGR and desired EEGR posi-
tions on a cold vehicle with a scan tool, the fault can be
easily verified. Check the Freeze Frame data to deter-
mine if the DTC set when the vehicle was cold by view-
ing the Engine Coolant Temperature (ECT).

1F–196 ENGINE CONTROLS
DAEWOO M-150 BL2
MAA1F230
DIAGNOSTIC TROUBLE CODE (DTC) – P1404 ELECTRIC EXHAUST GAS
RECIRCULATION CLOSED
Circuit Description
An Electric Exhaust Gas Re-circulation (EEGR) system
is used to lower oxides of nitrogen (NOX) emission lev-
els caused by high combustion temperatures. It a ac-
complishes this by feeding small amounts of exhaust
gases back into the combustion chamber. When the air/
fuel mixture is diluted with the exhaust gases, combus-
tion temperatures are reduced.
A linear EEGR valve is used on this system. The linear
EEGR valve is designed to accurately supply exhaust
gases to the engine without the use of intake manifold
vacuum. The valve controls exhaust flow going into the
intake manifold from the exhaust manifold fhrough an
orifice with a engine control module(ECM) controlled
pintle. The ECM controls the pintle position using inputs
from the Throttle Position (TP) and the Manifold Abso-
lute Pressure (MAP) sensor. The ECM then commands
the EEGR valve to operate when necessary by control-
ling an ignition signal through the ECM. This can be
monitored on a scan tool as the Desired EEGR position.
The ECM monitors the results of its command through a
feedback signal. By sending a 5 volt reference and a
ground to the EEGR valve, a voltage signal representing
the EEGR valve pintle position is sent to the ECM. This
feedback signal can also be monitored on a scan tool
and is the actual position of the EEGR pintle. The actual
EEGR position should always be near the commanded
or Desired EEGR position.
ThisDiagnostic Trouble Code(DTC) will detect an open
or short circuit.Conditions for Setting THE DTC

EEGR circuit high voltage.
Action Taken When The DTCs 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.

EEGR is disabled.
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.

Disconnecting the ECM battery feed for more than 10
seconds.
Diagnostic Aids
Due to moisture associated with exhaust systems, the
EEGR valve may freeze and stick in cold weather at
times. After the vehicle is brought into a warm shop for
repairs, the valve warms and the problem disappears.
By watching the Actual EEGR and desired EEGR posi-
tions on a cold vehicle with a scan tool, the fault can be
easily verified. Check the Freeze Frame data to deter-
mine if the DTC set when the vehicle was cold by view-
ing the Engine Coolant Temperature (ECT).

1F–200 ENGINE CONTROLS
DAEWOO M-150 BL2
MAA1F230
DIAGNOSTIC TROUBLE CODE (DTC) – P0405 EEGR PINTLE POSITION
SENSOR LOW VOLTAGE
Circuit Description
An Electric Exhaust Gas Re-circulation (EEGR) system
is used to lower oxides of nitrogen (NOX) emission lev-
els caused by high combustion temperatures. It a ac-
complishes this by feeding small amounts of exhaust
gases back into the combustion chamber. When the air/
fuel mixture is diluted with the exhaust gases, combus-
tion temperatures are reduced.
A linear EEGR valve is used on this system. The linear
EEGR valve is designed to accurately supply exhaust
gases to the engine without the use of intake manifold
vacuum. The valve controls exhaust flow going into the
intake manifold from the exhaust manifold fhrough an
orifice with a engine control module(ECM) controlled
pintle. The ECM controls the pintle position using inputs
from the Throttle Position (TP) and the Manifold Abso-
lute Pressure (MAP) sensor. The ECM then commands
the EEGR valve to operate when necessary by control-
ling an ignition signal through the ECM. This can be
monitored on a scan tool as the Desired EEGR position.
The ECM monitors the results of its command through a
feedback signal. By sending a 5 volt reference and a
ground to the EEGR valve, a voltage signal representing
the EEGR valve pintle position is sent to the ECM. This
feedback signal can also be monitored on a scan tool
and is the actual position of the EEGR pintle. The actual
EEGR position should always be near the commanded
or Desired EEGR position.
ThisDiagnostic Trouble Code(DTC) will detect an open
or short circuit.Conditions for Setting THE DTC

EEGR voltage is less than 0.01V.

EEGR potentiometer circuit low voltage.
Action Taken When The DTCs 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.

EEGR is disabled.
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.

Disconnecting the ECM battery feed for more than 10
seconds.
Diagnostic Aids
Due to moisture associated with exhaust systems, the
EEGR valve may freeze and stick in cold weather at
times. After the vehicle is brought into a warm shop for
repairs, the valve warms and the problem disappears.
By watching the Actual EEGR and desired EEGR posi-
tions on a cold vehicle with a scan tool, the fault can be
easily verified. Check the Freeze Frame data to deter-
mine if the DTC set when the vehicle was cold by view-
ing the Engine Coolant Temperature (ECT).

1F–204 ENGINE CONTROLS
DAEWOO M-150 BL2
MAA1F230
DIAGNOSTIC TROUBLE CODE (DTC) – P0406 EEGR PINTLE POSITION
SENSOR HIGH VOLTAGE
Circuit Description
An Electric Exhaust Gas Re-circulation (EEGR) system
is used to lower oxides of nitrogen (NOX) emission lev-
els caused by high combustion temperatures. It a ac-
complishes this by feeding small amounts of exhaust
gases back into the combustion chamber. When the air/
fuel mixture is diluted with the exhaust gases, combus-
tion temperatures are reduced.
A linear EEGR valve is used on this system. The linear
EEGR valve is designed to accurately supply exhaust
gases to the engine without the use of intake manifold
vacuum. The valve controls exhaust flow going into the
intake manifold from the exhaust manifold fhrough an
orifice with a engine control module(ECM) controlled
pintle. The ECM controls the pintle position using inputs
from the Throttle Position (TP) and the Manifold Abso-
lute Pressure (MAP) sensor. The ECM then commands
the EEGR valve to operate when necessary by control-
ling an ignition signal through the ECM. This can be
monitored on a scan tool as the Desired EEGR position.
The ECM monitors the results of its command through a
feedback signal. By sending a 5 volt reference and a
ground to the EEGR valve, a voltage signal representing
the EEGR valve pintle position is sent to the ECM. This
feedback signal can also be monitored on a scan tool
and is the actual position of the EEGR pintle. The actual
EEGR position should always be near the commanded
or Desired EEGR position.
This Diagnostic Trouble Code(DTC) will detect an open
or short circuit.Conditions for Setting THE DTC

EEGR voltage is higher than 4.99V.

EEGR potentiometer circuit high voltage.
Action Taken When The DTCs 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.

EEGR is disabled.
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
Due to moisture associated with exhaust systems, the
EEGR valve may freeze and stick in cold weather at
times. After the vehicle is brought into a warm shop for
repairs, the valve warms and the problem disappears.
By watching the Actual EEGR and desired EEGR posi-
tions on a cold vehicle with a scan tool, the fault can be
easily verified. Check the Freeze Frame data to deter-
mine if the DTC set when the vehicle was cold by view-
ing the Engine Coolant Temperature (ECT).

1F–208 ENGINE CONTROLS
DAEWOO M-150 BL2
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.

1F–210 ENGINE CONTROLS
DAEWOO M-150 BL2
MAA1F240
DIAGNOSTIC TROUBLE CODE (DTC) – P0444 EVAP PURGE CONTROL
CIRCUIT NO SIGNAL
Circuit Description
The evaporative emission (EVAP) system includes the
following components :

Fuel tank.

EVAP vent solenoid.

Fuel pipes and hoses.

Fuel vapor lines.

Fuel cap.

EVAP canister.

Purge lines.

EVAP canister purge valve.

EVAP service port.
The evaporative emission system is checked by apply-
ing vacuum to the EVAP system and monitoring for a
vacuum decay. The engine control module(ECM) moni-
tors the vacuum level through the fuel tank pressure
sensor signal. At the appropriate time, the EVAP canis-
ter purge valve and the EVAP vent solenoid are turned
on, allowing the engine to draw a small vacuum on the
entire EVAP system. After the desired vacuum level has
been achieved, the EVAP canister purge valve is turned
OFF, sealing the system. If a sufficient vacuum level
cannot be achieved, a large leak is indicated. This can
be caused by the following conditions :
Missing or faulty fuel cap.
Disconnected or faulty fuel tank pressure sensor.
Disconnected, damaged, pinched, or blocked EVAP
purge line.
Disconnected or faulty EVAP canister purge valve.
Disconnected or faulty EVAP vent solenoid.Open ignition feed circuit to the EVAP vent or purge so-
lenoid.
Damaged EVAP canister.
Leaking fuel sensor assembly O-ring.
Leaking fuel tank or fuel filler beck.
Any of the above conditions can set DTC P0444.
The test is failed if the tank vacuum is less than 10 in
H20 for 15 seconds and the manifold vacuum integral is
greater than 49512 (proportional to purge mass from the
tank).
Conditions for Setting the DTC

Intake Air Temperature(IAT) is between 4°C and
34°C(39°F and 93°F).at engine start up.

Engine Coolant Temperature(ECT) is between 4°C
and 34°C(39°F and 93°F).at engine start up.

Barometric pressure (BARO) is greater than 68kPA.

IAT is not more than 8°C(46°F) greater than the ECT
at start up.

Fuel level is between 10% and 90%.

The throttle position (TP) sensor is less than or equal
to 100%.

No fuel slosh, and the change in fuel level percent is
21 counts on 0.125 sec.

Manifold vacuum is greater than or equal to 10kPA.

Fuel level or change in tank pressure is less than or
equal to 24.9 in H2O.

System voltage is between 11V and 16V.

1F–214 ENGINE CONTROLS
DAEWOO M-150 BL2
MAA1F240
DIAGNOSTIC TROUBLE CODE (DTC) – P0445 EVAP PURGE CONTROL
CIRCUIT FAULT
Circuit Description
The evaporative emission (EVAP) system includes the
following components :

Fuel tank.

EVAP vent solenoid.

Fuel tank pressure sensor.

Fuel pipes and hoses.

Fuel vapor lines.

Fuel cap.

EVAP canister.

Purge lines.

EVAP canister purge valve.

EVAP service port.
The evaporative emission system is checked by apply-
ing vacuum to the EVAP system and monitoring for a
vacuum decay. The engine control module(ECM) moni-
tors the vacuum level through the fuel tank pressure
sensor signal. At the appropriate time, the EVAP canis-
ter purge valve and the EVAP vent solenoid are turned
on, allowing the engine to draw a small vacuum on the
entire EVAP system. After the desired vacuum level has
been achieved, the EVAP canister purge valve is turned
OFF, sealing the system. If a sufficient vacuum level
cannot be achieved, a large leak is indicated. This can
be caused by the following conditions :
Missing or faulty fuel cap.
Disconnected or faulty fuel tank pressure sensor.
Disconnected, damaged, pinched, or blocked EVAP
purge line.
Disconnected or faulty EVAP canister purge valve.Disconnected or faulty EVAP vent solenoid.
Open ignition feed circuit to the EVAP vent or purge so-
lenoid.
Damaged EVAP canister.
Leaking fuel sensor assembly O-ring.
Leaking fuel tank or fuel filler beck.
Any of the above conditions can set DTC P0445.
The test is failed if the tank vacuum is less than 10 in
H20 for 15 seconds and the manifold vacuum integral is
greater than 49512 (proportional to purge mass from the
tank).
Conditions for Setting the DTC

Intake Air Temperature(IAT) is between 4°C and
34°C(39°F and 93°F).at engine start up.

Engine Coolant Temperature(ECT) is between 4°C
and 34°C(39°F and 93°F).at engine start up.

Barometric pressure (BARO) is greater than 68kPA.

IAT is not more than 8°C(46°F) greater than the ECT
at start up.

Fuel level is between 10% and 90%.

The throttle position (TP) sensor is less than or equal
to 100%.

No fuel slosh, and the change in fuel level percent is
21 counts on 0.125 sec.

Manifold vacuum is greater than or equal to 10kPA.

Fuel level or change in tank pressure is less than or
equal to 24.9 in H2O.

System voltage is between 11V and 16V.

1F–246 ENGINE CONTROLS
DAEWOO M-150 BL2
MAA1F070
DIAGNOSTIC TROUBLE CODE (DTC) 0505
IDLE AIR CONTROL VALVE (IACV) CIRCUIT FAULT
Circuit Description
The Engine Control Module (ECM) controls the air en-
tering into the engine with an Idle Air Control (IAC)
Valve. To increase the idle rpm, the ECM commands the
pintle inside the IAC valve away from the throttle body
seat. This allows more air to bypass through the throttle
blade. To decrease the rpm the ECM commands the
pintle towards the throttle body seat. This reduces the
amount of air bypassing the throttle blade. A scan tool
will read the IAC valve pintle position in counts. The
higher the counts, the more air that is allowed to bypass
the throttle blade. This Diagnostic Trouble Code (DTC)
determines if a low idle condition exists as defined as
100 rpm below the desired idle rpm.
Conditions for Setting the DTC

No intrusive tests are active.

DTC(s) P0106, P0107, P0108, P0112, P0113,
P0117, P0118, P0122, P0123, P0131, P0132,
P0133, P1133, P1134, P0171, P1171, P0172, P0201,
P0202, P0203, P0204, P0300, P0336, P0337,
P0341, P0342, P0351, P0352, P0402, P0404,
P1404, P0405, P0406, P0443, and P0502 are not
set.

Engine is running more than 60 seconds.

Barometric Pressure (BARO) is greater than 72 kPa
(10.4 psi).

Engine Coolant Temperature (ECT) is greater than
60C (140F).

Ignition voltage is between 11 and 16 volts.

The Intake Air Temperature (IAT) is greater than
–20C (–4F).

Manifold Absolute Pressure is less than 60 kPa (8.7
psi).
IAC valve is controlled fully opened.

All of the above must be met for greater than 5 sec-
onds.
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.

Disconnecting the ECM battery feed for more than 10
seconds.
Diagnostic Aids
Inspect the IAC valve electrical connection for proper
mating.
Inspect the wiring harness for damage.
Inspect the throttle stop screw for signs of tampering.
Inspect the throttle linkage for signs of binding or exces-
sive wear.
A slow or unstable idle may be caused by one of the fol-
lowing conditions:

Fuel system too rich or too lean.

Foreign material in the throttle body bore or in the air
induction system.

A leaking or restricted intake manifold.

ENGINE CONTROLS 1F–263
DAEWOO M-150 BL2
DIAGNOSTIC TROUBLE CODE (DTC) – P0604 ENGINE CONTROL MODULE
INTERNAL/EXTERNAL RAM ERROR
Circuit Description
The engine control module (ECM) is the control center
of the fuel injection system. It constantly looks at the in-
formation from various sensors, and controls the sys-
tems that after vehicle performance. The ECM also
performs the diagnostic function of the system. It can
recognize operational problems, alert the driver through
the Malfunction Indicator Lamp (MIL), and store a Diag-
nostic Trouble Code (DTC) or DTCs which identify the
problem areas to aid the technician in making repairs.
An electrically erasable programmable read only
memory (EEPROM) is used to house the program infor-
mation and the calibrations required for engine, trans-
axle, transaxle diagnostics operation. The ECM uses a
value called a checksum for error detection of the soft-
ware. The checksum is a value that is equal to all the
numbers in the software added together. The ECM adds
all the values in the software and if that value does not
equal the checksum value, a checksum error is indi-
cated.Conditions for Setting the DTC

The ECM detects more than 3 incorrect checksum.
Action taken when The DTCs 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.

Coolant fan turns on.
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.
DTC P0604 – Engine Control Module RAM Error
StepActionValue(s)YesNo
1
Perform an On-Board Diagnostic (EOBD) System
Check.
Is the system check complete?
–
Go to Step 2
Go to
“On-Board
Diagnostic
System Check”
2Replace the engine control module(ECM).
Is the replacement complete?–Go to Step 3–
3
1. Using the scan tool, clear the DTCs.
2. Start the engine and idle at normal operating
temperature.
3. Operate the vehicle within the conditions for
setting this DTC ad specified in the supporting
text.
Does the scan tool indicate that this diagnostic has
run and passed?
–
Go to Step 4Go to Step 2
4
Check if any additional DTCs are set.
Are any DTCs displayed that have not been
diagnosed?
–
Go to
applicable DTC
table
System OK