Honda Civic Service Manual page 220

ECM Data
You can retrieve data from the ECI\4 by connecting the OBD ll scan tool or the Honda PGM Tester to the data link
connector (DLC). The items listed in the table below conform to SAE recommended practice. The Honda PGM Tester
also reads data beyond that recommended by SAE to help you find the causes of intermittent problems.
The "operating values" listed are approximate and may vary depending on the environment and the individual
v e h i c l e .
Unless noted otherwise, "at idle speed" means idling with the engine completely warmed up in the neutral position,
and the A,/C and all
Diagnostic
Trouble Code
(DTC}
lf the ECM delects a problem, it will store it as a code
consisting of one letter and four numbers. Depending on
the problem, an SAE-defined code (Poxxx) or a Honda,
defined code {P1xxx) will be output to the tester.
The ECI\4 computes engine speed from the signals sent
from the crankshaft position (CKP) sensor. This data is
used for determining the time and amount of injected fuel.
detected, there is no
ourpul.
l f n o p r o b l e m i s
Y E S
N e a r l y t h e s a m e a s
tachometer indication
At idle speed;
The ECM converts pulse signals from the vehicle speed
sensor (VSS).
N e a r l y t h e s a m e a s
speedometer
i n d i c a t i o n
M a n i f o l d
Absolute
Pressure
(MAP)
The absolute pressure caused in the intake manifold by
e n g i n e l o a d a n d s p e e d .
With engine stopped: YES
Nearly the same as
almospnenc pressure.
At idle speed: about
20 4'1 kPa
( 1 5 0 3 1 0 m m H g ,
6 - 1 2 i n . H q ) . 0 . 7 1 . 3 V
The ECT sensor converts coolant temperature into voltage
and signals the ECM. The sensor is a thermistor whose
internal resistance changes with coolant tempetature. The
ECM uses the voltage signals from the ECT sensor to
determine the amount of injected fuel.
W i t h c o l d e n g i n e :
S a m e a s a m b i e n t
temperature and IAT
With engine warmed
u p ; a b o u t 1 1 6 2 ' 1 2 " F
1 0 0 ' c ) . 0 . 5 - 0 . 8 v
Air Fuel Ratio The A,/F sensor detects the oxygen content in the exha ust
0.0 - 1 .25 V
( A y ' F ) S e n s o r .
g a s a n d s e n d s v o l t a g e s i g n a l s t o t h e E c l v l , B a s e d o n t h e s e
8 . 0 1 1 . 0 m A ( P G M
(Sensor 1)
signals, the ECM controls the airlfuel ratio. When the I Tester)
oxygen content is high (that is, when the ratio is leaner
At idle speed:
than the stoichiometric ratio), the voltage signal is Iower.
about 0.1 0.9 V
When the oxygen content is low (that is, when the ralio is
richer than the stoichiometric ratio). the voltage signal is
higher. The A'lF sensor signals are electrical current that
are indicated as voltaqe on the
The HO2S detects the oxygen content in the exhaust gas
a n d s e n d s v o l t a g e s i g n a l s t o t h e E C M . B a s e d o n t h e s e
signals, the ECM controls the airlfuel 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
r i c h e r t h a n t h e s t o i c h i o m e t r i c r a t i o ) , t h e v o l t a g e s i g n a l i s
Secondary
Heated
Oxygen
Sensor
(Secondary
H 0 2 S ,
Sensor2)
0 . 0 1 . 2 5 V N O
At idle speed:
a b o u t 0 . 1 0 . 9 V
(cont'd)
1 1 - 1 3