Base idle HONDA CIVIC 2000 6.G Workshop Manual

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 beretrieved 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 andthe individual vehicle.. 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.
(
DataDescriptionOperating ValueFreeze Data
Diagnostic
Trouble Code(DTC)
lf the ECM /PCM detects a problem, it will store it as acode 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 therester.
lf no problem is detected,
there is no output.
YES
Engine SpeedThe ECM/PCM computes engine speed from the signalssent from the Crankshaft Position sensor.This data is used for determining the time and amount offuel injection,
Nearly the same as
tachometer indication.YES
Vehicle SpeedThe ECM/PCM converts pulse signals from the VehicleSpeed Sensor (VSS) into speed data.Nearly the same as
speedometer indicationYES
Manifold
Absolute
Pressure {MAP)
The absolute pressure caused in the intake manifold bvengine load and speed.With engine stopped:
Nearly the same as atmo-
spheflc pressure
At idle speed:
24 - 31 kPa (180 - 280
mmHg, 7.1 - 11.0 inHg)
YES
Engine Coolant
Temperature
(ECT)
The ECT sensor converts coolant temperature into volt_age and signals the ECM/PCM. The sensor is a thermistorwhose internal resistance changes with coolant temDera_ture. The ECM/PCM uses the voltage signals from theECT 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,
Sensor 1)(Secondary
Sensor 2)
The Heated Oxygen Sensor detects the oxygen contentin the exhaust gas and sends voltage signals to theECI\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 stoichiometricratio), the voltage signal is lower.When the oxygen content is low (that is, when the ratiois richer than the stoichiometric ratio), the voltage signalis higher.
0.0 - 1.25 V
At idle speed:
about 0.1 - 0.9 V
NO(Sensor 1)
1 1-86

DataDescriotion
Loop status is indicated as "open" or "closed"'
Closed: Based on the HO2S output, the ECM/PCM deter-
mines the airlfuel ratio and controls the amount of inject-
ed fuel.
Open: lgnoring HO2S output, the ECM/PCM refers to sig-
nals from the TP, MAP, and ECT sensors to control the
amount of injected fuel.
The air/fuel ratio correction coefficient for correcting the
amount ot injected fuel when H02S feedback is in the
closed loop status When the signal from the HO2S is
weak, short term fuel trim gets higher, and the ECM/PCM
increases the amount of injected fuel The airlfuel ratio
gradually gets richer, causing a higher HO2S output
Consequently, the short term fuel trim is lowered, and
the ECMiPCM reduces the amount of injected fuel
This cvcle keeps the airlfuel ratio close to the stoichio-
metric ratio when in closed loop status'
Operating ValueF eeza Data
HO2S
Feedback
Loop Status
At idle speed: closed
YES
Short Term
Fuel Trim
! 20%
YES
Long Term
Fuel Trim
Long term fuel trim is computed from shon term fuel
trim and indicates changes occurring in the fuel supply
svstem over a long Period
lf long term fuel trim is higher than 1.00, the amount of
injecGd fuel must be increased. lf it is lower than 1 00'
the amount of injected fuel must be reduced'
! 20%
YES
lntake Air
Temperature
{IAT)
The IAT sensor converts intake air temperature into volt-
age and signals the ECM/PCM. When intake air tempera-
ture is low, the internal resistance of the sensor
increases. and the voltaqe signal is higher'
With cold engine:
Same as ambient temPer'
ature and ECTYES
At idle speed:
approx. 10 %YESThrottle
Position
Based on the accelerator pedal position, the open'ng
angle of the throttle valve is indicated
lgnition
Timing
lgnition timing is the ignition advance angle set by the
gCV/eCV. tn" gCU/PCM matches ignition timing to the
driving conditions.
CLV is the engine load calculated from the MAP data'
At idle speed: 12'i 2'
(81642 engine: 16" t 2")
BTDC with the SCS ser-
vice connector connected.
NO
Calculated
Load Value
{CLV)
At idle speed:
15-35%
At 2.500 rpm with no load:
12 - 30%
YES
ro
11-87

I
L
1D16Y5, D16Y8 engine with M/T 81642 engine)I
D16Y7 engine:
{From page 11-192)
Check the IAC valve:Disconnect the 3P connector from
the IAC valve.
Check the IAC valve:Disconnect the 2P connectorfrom the IAC valve.
Does the engine speed drop or
the engine stall?
Adiust the {base} idle speod (see
page 11-220 - 2231.It it's impos-
aible, clean the ports in lhe throt'
tle bodv,
(From page 11-192i
Check Ior vacuum leaks:1. Turn the ignition switch OFF.2. Remove the intake air ductfrom the throttle body.
3. Start the engine and let it idle.
4. Put your finger on the lowerpon in the th.ottle body.
Ch€ck tor vecuum loaks, m.kesure the throttle valve is com_pletaly closed, end repair as nec-Does the engine speed droP?
Adiust the idle speed (see page
11-220 - 2231. lf it's impossible,
reolace the IAC velve.UPPERPORT
1 1-1 93