Honda Odyssey 2004. Manual — part 78
S0X4A00A20300000000CAAT00
Electronic Control System
Fail-safe Function
Back-up Function
Self-diagnosis
Two Driving Cycle Detection Method
11-10
Fuel and Emissions Systems
System Descriptions
The functions of the fuel and emission control systems are managed by the powertrain control module (PCM).
When an abnormality occurs in the signal from a sensor, the PCM ignores that signal and assumes a pre-programmed
value for that sensor that allows the engine to continue to run.
(MIL) and stores the diagnostic trouble code (DTC) in erasable memory. When the ignition is first turned on, the PCM
supplies ground to the MIL for 2 seconds (’99-01 models) or for 15 to 20 seconds (’02-04 models) to check the MIL bulb
condition.
To prevent false indications, the ‘‘two driving cycle detection method’’ is used for some self-diagnostic functions.
When an abnormality occurs, the PCM stores it in its memory. When the same abnormality recurs after the ignition
switch is turned OFF and ON (II) again, the PCM turns on the MIL.
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When an abnormality occurs in the PCM, the injectors are controlled by an independent back-up circuit to permit
minimal driving.
When an abnormality occurs in the signal from a sensor, the PCM supplies ground for the malfunction indicator lamp
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PCM Data
Data
Description
Operating Value
Freeze Data
11-11
You can retrieve data from the PCM by connecting the OBD II scan tool or HDS to the data link connector (DLC). The
items listed in the table below conform to SAE recommended practice. The HDS also reads data beyond that
recommended by SAE to this data may help you find the causes of intermittent problems.
NOTE:
• The ‘‘operating values’’ listed are approximate and may vary depending on the environment and the individual
vehicle.
• Unless noted otherwise, ‘‘at idle speed’’ means idling with the engine completely warmed up, the transmission in
park or neutral, and the A/C and all accessories turned off.
Diagnostic
Trouble Code
(DTC)
If the PCM detects a problem, it will store it as a code
consisting of one letter and 4 numbers. Depending on the
problem, as SAE-defined code (P0xxx) or a Honda-defined
code (P1xxx) will be output to the tester.
If no problem is
detected, there is no
output.
YES
Engine Speed
The PCM computes engine speed from the signals sent
from the Crankshaft Position (CKP) sensor. This data is
used for determining the time and amount of fuel
injection.
Nearly the same as
tachometer
indication
At idle speed: 730
50 rpm
YES
Vehicle Speed
The PCM converts pulse signals from the output shaft
(countershaft) speed sensor into speed data.
Nearly the same as
speedometer
indication
YES
Manifold
Absolute
Pressure (MAP)
The absolute pressure caused in the intake manifold by
engine load and speed.
With engine stopped:
Nearly the same as
atmospheric
pressure.
At idle speed: about
20
34 kPa (150
260 mmHg, 6
10
in.Hg), 0.9
1.1 V
YES
Engine Coolant
Temperature
(ECT)
The ECT sensor converts coolant temperature into voltage
and signals the PCM. The sensor is a thermistor with
internal resistance that changes with coolant temperature.
The PCM uses the voltage signals from the ECT sensor to
determine the amount of injected fuel.
With cold engine:
Same as ambient
temperature and IAT
With engine warmed
up: about 176
212°F
(80
100°C), 0.5
0.7 V
YES
Primary Heated
Oxygen Sensor
(Primary HO2S)
(Sensor 1),
Secondary
Heated Oxygen
Sensor
(Secondary
HO2S)
(Sensor 2)
The HO2S detects the oxygen content in the exhaust gas
and sends voltage signals to the PCM. Based on these
signals, the PCM controls the air fuel ratio. When the
oxygen content is high (that is, when the ratio is leaner
than the stoichiometric ratio), the voltage signal is lower.
When the oxygen content is low (that is, when the ratio is
richer than the stoichiometric ratio), the voltage signal is
higher.
0.0
1.25 V
At idle speed:
about 0.1
0.9 V
(cont’d)
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PCM Data (cont’d)
Data
Description
Operating Value
Freeze Data
11-12
Fuel and Emissions Systems
System Descriptions (cont’d)
Fuel System
Status
Fuel system status is indicated as ‘‘open’’ or ‘‘closed’’.
Closed: Based on the HO2S output, the PCM determines
the air/fuel ratio and controls the amount of injected
fuel.
Open: Ignoring HO2S output, the PCM refers to signals
from the Throttle Position (TP), Manifold Absolute
Pressure (MAP), Intake Air Temperature (IAT),
Barometric Pressure (BARO) and Engine Coolant
Temperature (ECT) sensors to control the amount of
injected fuel.
At idle speed: closed
YES
Short Term Fuel
Trim
The air/fuel ratio correction coefficient for correcting
the amount of injected fuel when the fuel system status
is ‘‘closed’’. When the ratio is leaner than the
stoichiometric ratio, the PCM increase short term fuel
trim gradually, and the amount of injected fuel
increases. The air/fuel ratio gradually gets richer,
causing a lower oxygen content in the exhaust gas.
Consequently, the short term fuel trim is lowered, and
the PCM reduces the amount of injected fuel. This cycle
keeps the air/fuel ratio close to the stoichiometric ratio
when in closed loop status.
0.6
1.5
YES
Long Term Fuel
Trim
Long term fuel trim is computed from short term fuel
trim and indicates changes occurring in the fuel supply
system over a long period.
If long term fuel trim is higher than 1.00, the amount of
injected fuel must be increased. If it is lower than 1.00,
the amount of injected fuel must be reduced.
0.8
1.2
YES
Intake Air
Temperature
(IAT)
The IAT sensor converts intake air temperature into
voltage and signals the PCM. When intake air
temperature is low, the internal resistance of the sensor
increases, and the voltage signal is higher.
With cold engine:
Same as ambient
temperature and ECT
YES
Throttle Position
Based on the accelerator pedal position, the opening
angle of the throttle valve is indicated.
At idle speed:
about 10 %, 0.5 V
YES
Ignition Timing
Ignition timing is the ignition advance angle set by the
PCM. The PCM matches ignition timing to the driving
conditions.
At idle speed:
10°
2° BTDC when the
SCS service signal line
is jumped with the HDS
NO
Calculated Load
Value (CLV)
CLV is the engine load calculated from the MAP data.
At idle speed:
16
33 %
At 2,500 rpm with no
load:
18
26 %
YES
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PCM Electrical Connections
’99-00 Models
11-13
IGNITION SWITCH
B
IG1
ST
PGM-FI MAIN RELAY
P
FUEL
PUMP
BATTERY
No. 1
No. 2
No. 3
No. 4
No. 5
No. 6
MIL
IAC VALVE
F
TDC
SENSOR 1
D
B
IMMOBILIZER
INDICATOR
DATA
LINK
CONNECTOR
To ELD
To SPEEDOMETER
ALT
KS C22
A/C CLUTCH RELAY
RADIATOR FAN RELAY,
RADIATOR FAN SWITCH
A/C SWITCH
To
To
To
D
STARTER
CUT
RELAY
E
C
A
IMOIND A12
B1 IGP1
B9 IGP2
A24 STSW
B21 VBU
B20 LG1
B22 LG2
PG1 B2
PG2 B10
IMOFPR A15
INJ1 B11
INJ2 B5
INJ3 B15
INJ4 B4
INJ5 B3
INJ6 B6
IACV B23
C20 TDC1
C8 CKP
C9 CKP
A30 ELD
A9 VSSOUT
MIL A18
INJECTORS
A10 SCS
ALTC C2
ALTF C5
A21 K-LINE
ACC A17
FANC A20
ACS A27
TDC
SENSOR 2
CKP
SENSOR
KNOCK
SENSOR
C21 TDC1
C29 TDC2
C30 TDC2
B
FUSES:
BACK UP, ACC (40A) *
STOP (20A) *
ACGS (15A)*
BATTERY (120A) *
IG MAIN (50A) *
No. 1 FUEL PUMP (15A) *
No. 11 IG COIL (15A) *
No. 6
No. 9
No. 13 STARTER SIGNAL (7.5A) *
No. 13 CLOCK BACKUP (7.5 A) *
BACK UP LIGHT
INSTRUMENT LIGHT (7.5A) *
* : in the under-hood fuse/relay box
* : in the driver’s under-dash fuse/relay box
* : in the passenger’s under-dash fuse/relay box
ECU (PCM)
CRUISE CONTROL (15A) *
A
A
A
A
A
B
B
B
C
B
A
B
C
B
(cont’d)
03/07/29 09:17:49 61S0X050_110_0013
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