Honda Civic Service Manual page 356

Troubleshooting
Troubleshooting Procedures (cont,dl
ECM/PCM Data
By connecting the OBD ll scan tool or the Honda pGM Tester to the l6p data link connector (DLC),
various data can be
retrieved from the EcM/PcM. The items Iisted in the table below conform to the sAE recommended practice.
The Honda PGM Tester also reads data beyond that recommended bv SAE.
understanding this data wil help to find the causes of intermittent fairures or engine probrems,
NOTE:
'
The "operating values" given below are approximate values and may be different depending
on the environment and
t h e i n d i v i d u a l v e h i c l e .
.
Unless noted otherwise, "at idle speed,, means idling with the engine completely warmed
up, Ay'T in position @ or E],
M/T in neutral, and the Ay'C and all accessories turned off.
(
Data
Description
Operating Value
Freeze Data
Diagnostic
Trouble Code
(DTC)
lf the ECM /PCM detects 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 (Plxxx) will be outDut to the
rester.
lf no problem is detected,
there is no output.
YES
Engine Speed
The ECM/PCM computes engine speed from the signals
sent from the Crankshaft Position sensor.
This data is used for determining the time and amount of
fuel injection,
Nearly the same as
tachometer indication.
YES
Vehicle Speed
The ECM/PCM converts pulse signals from the Vehicle
Speed Sensor (VSS) into speed data.
Nearly the same as
speedometer indication
YES
Manifold
Absolute
Pressure {MAP)
The absolute pressure caused in the intake manifold bv
engine load and speed.
With engine stopped:
Nearly the same as atmo-
spheflc pressure
At idle speed:
24 - 31 kPa (180 - 280
m m H g , 7 . 1 - 1 1 . 0 i n H g )
YES
E n g i n e C o o l a n t
Temperature
(ECT)
The ECT sensor converts coolant temperature into volt_
age and signals the ECM/PCM. The sensor is a thermistor
whose internal resistance changes with coolant temDera_
ture. The ECM/PCM uses the voltage signals from the
ECT sensor to determine the amount of iniected fuel.
With cold engine:
Same as ambient temper,
ature and IAT
With engine warmed up:
176 - 194.F (80 - 90.C)
YES
Heated Oxygen
Sensor {HO2S)
(Primary,
S e n s o r 1 )
(Secondary
Sensor 2)
The Heated Oxygen Sensor detects the oxygen content
in the exhaust gas and sends voltage signals to the
ECI\4/PCM. Based on these signats, the ECM/pCM con_
trols 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 richer than the stoichiometric ratio), the voltage signal
is higher.
0 . 0 - 1 . 2 5 V
At idle speed:
about 0.1 - 0.9 V
N O
( S e n s o r 1 )
1 1 - 8 6