
ECM Data
By connecting the OBD ll scan tool or the Honda PGM Tester to the 16P data link connector (DLC), various data can beretrieved from the EcM The items risted in the tabre berow conform to the sAE recommended practice.The Honda PGM Tester also reads data beyond that recommended bv SAE.understanding this data wirl herp to rind the causes of intermiftent fairures or engine probrems.
NOTE:
' The "operatlng values" given below are approximate values and may be different depending on the environment andthe individual car.' Unless noted otherwise, "at idle speed" means idling with the engiFe completely warmed up, transmissron in park orneutral and the A,/C and all accessories turned off.
DataDescriptionOperating ValueFreeze Data
Diagnostic
Trouble Code(DTC)
lf the ECM detects a problem, it will store tt as a cocteconsisting ot one letter and four numbers.Depending on the problem, an SAE-defined code{Poxxx) or a Honda-defined code (plxxx) will beoutput to the lester.
lf no problem is detected,
there is no output.
YES
Engine SpeedThe ECM computes engine speed from the signalssent from the Crankshaft Position sensor.This data is used for determining the I|me andamount of fuel injection.
Nearly the same as
tachometer indication at
idle speed:
81881,818C1 engines:
750 t 50 rpm
818C5 engine:
800 1 50 rpm
YES
Vehicle SpeedThe ECM converts pulse signals trom the VehicleSpeed Sensor (VSS) into speed data.
Nearly the same as
speedometer indicationYES
Manitold
Absolute
Pressure {MAP)
The absolute pressure created in the intake manifoldby engine load and speed.With engine stopped:
Nearly the same as atmo
spheric pressure. At idle
speed:
24 - 37 kPa (180 - 280
mmHg,7.1 1'1.0 inHg)
YES
Engine Coolant
Temperature
(ECT)
The ECT sensor converts coolant temperature intovoltage and signals the ECM. The sensor is a thermis-tor whose internal resistance changes with coolanttemperature. The ECM uses the voltage signals fromlhe ECT sensor to determine the amount of iniectedfuel.
With cold engine:
Same as ambient temper
ature and IAT
With engine warmed up:
approx. 176 - 200'F
{80 - 93.C)
, YES
Heated Oxygen
Sensor (HO2S)
{sensor 1)(sensor 2)
The Heated Oxygen Sensor detects the oxygen con-tent in the exhaust gas and sends voltage signals tothe ECM. Based on these signals,lhe ECM controlsthe airlfuel ratio. When the oxygen content is high{that is, when the ratio is leaner than the stoichiomericratio), the voltage signal is lower. When the oxygencontent is low (that is, when the ratio is richer thanthe stoichiomeric ratio), the voltage signal is higher.
0.0 - 1.25 V
At idle speed:
abour 0.'1 - 0.9 V(sensor I )NO(sensor 1)
(conl'd)
11-37

ldle Control System
Fast ldle Thermo Valve (A/T model onlylFast ldle I nermo valve (A/ | mooel
Description
To prevent erratic running when the engine is warming
up. it is necessary to raise the idle speed. The fast idle
thermo valve is controlled by a thermowax plunger.
When the engine is cold, the engine coolant surround-
ing the thermowax contracts the plunger, allowing addi
tional air to be bvoassed into the intake manifold so that
the engine idles taster. When the engine reaches operat-
ing temperature, the valve closes. reducing the amount
of air bypassing into the manifold.
FAST IDLE THERMO
VALVE
VALVE
wAx
Inspection
NOTE: The fast idle thermo valve is factory adiusted; it
should not be disassembled.
1. Remove the intake air duct from the throttle body.
2. Start the engine.
3. Put your finger over the lower port in throttle body
and make sure that there is air flow with the engine
cold {engine coolant temperature below 86'F, 30"c).
LOWERPORT
lf there is no air flow, replace the last idle thermo
valve and retest.
Start the engine. Hold the engine at 3,000 rpm with
no load (in Park or neutral) until the radiator fan
comes on, then let it idle.
Check that valve is completely closed. lf not, air suc-
tion can be felt at the lower port in the throttle body.
l{ any suction is felt, the valve is leaking. Check
engine coolant level and for air in the engine
coolant system (see section 10). It OK, replace the
fast idle thermo valve and recheck.
5.
{1.0 kg.m,7.2lbftl
l
11-110
lL.

t"iI
Emission Gontrol System
System Description
Three Way Catalytic Converter (TWCI
\
t
The emission control system includes a Three Way
Catalytic Converter (TWC), Positive Crankcase Ventilation
(PCV) system and Evaporative Emission (EVAP) Control
system. The emission control system is designed to meet
tederal and state emission standards.
InsDeciion
!@@ Do not smoke during this procedure. Keep
any open llame away from your work area.
1. Start the engine. Hold the engine at 3,000 rpm with
no load {in Park or neutral) until the radiator fan
comes on, then let it idle.
2. Connect a tachometer.
Check and adjust the idle speed, if necessary (see
page '11-11 ! ).
Warm up and calibrate the CO meter according to the
meter manufacturer's instructions.
Check idle CO with rhe headlights, heater blower,
rear window defogger, cooling fan, and air condition-
er off.
NOTE: {Canada) Pull the parking brake lever up.
Start the engine, then check that the headlights are
olf.
CO meter should indicste 0.17o maximum.
DescriDtion
The Three Way Catalytic Converter {TWC) is used to convert hydrocarbons (HC), carbon monoxide (CO), and oxides of
nitrogen (NOx) in the exhaust gas, to carbon dioxide (COr), dinitrogen {Nr) and water vapor.
Bl8Cl engine l818Bl, 818C5 engines is similar):
FRONT OFVEHICLE
PRIMAEYHEATEDOXYGEN SENSORIPRIMARY HO2S}
HOUSING
WAYCATALYSTS
SECONOARYHEATEDOXYGEN SENSOR{SECONDARYH02St
\

Throttle Control Cable
Inspection
NOTE: Before inspecting the throttle controlcable, makesure:
a Throttle cable tree play is correct (see section I 1).a ldle speed is correct (see section 1l).a To warm up the engine to normal operating tempera-
ture (the cooling fan comes on).
1 . Verify that the throttle control cable is clamped cor-rectly in three positions.
CONTROL CABLE
LOWERHOSEClamp at the end ofblue tape on the cable.
Verily that the throttle controldrum is synchronized
with the throttle linkage while depressing and releas-
ing the accelerator pedal.
ll the throttle control drum is not synchronized with
the throttle linkage, adjust rhe throttle control cable.
(cont'd)
14-179

Adjustment
NOTE: Before adjusting the throttle controlcable, make
sure:
a Throttle cable lree play is correct (see section 11).a ldle speed is correct (see section 11).a To warm up the engine to normal operating tempera-
ture {the cooling fan comes on)
1 . Verify that the throttle control cable is clamped correctly in three positions.
THROTTLEATF COOLERPIPE
LOWERHOSEClamp at the end ofblue tape on the cable.
Verily that the throttle linkage is in the fully-closedposttron.
Loosen the locknut of the throttle control cable at
the throttle linkage.
CONTROL CABLE
LOCKNUTS
14-181
Push in this directron.
Remove the free play of the throttle control cable
with the locknut, while pushing the throttle control
drum to the tull-closed potision as shown.
5. Tighten the locknuts.
6.After tightening the locknuts, inspect the synchroni-
zation and throttle control drum movement.

SYMPTOMREMEDY
Hot air tlow is low.Blower motor runs, but one or more
speeds are inoperative.
Follow the flowchart (see page 21-9).
Blower runs propetly.Check for the following:. Clogged heater duct
. Clogged heater outlet
. Incorrect door Position
No hot air tlowBlower motor does not run at all.Follow the flowchart {see page 21-11}
Blower motor runs.Check for the following:
. clogged heater duct
. Clogged blower outlet. Clogged heatet valve
. Faultv air mix door
. Heater valve cable adjustment lsee page 21-27].
. Air mix control cable adiustment {see page 21-27)
. Faulty thermostat (see section 10)
. Clogged evsporator (with air conditioning)
. Frozen evaDorator (with air conditioning)
Mode control motor does not run, or one or more mooes are
inoDeratave.
Follow the flowchart (see page 21-14).
Recirculation control door does not change between FRESH
and RECIRCULATE.
Follow the flowchart {see page 21-17).
Troubleshooting
Symptom Chart
NOTE: Check the engin€ coolant level and allow the engine to warm up before troubleshooting'
21-8
v