1987 MAZDA 626 air condition

CONTROL SYSTEM 4B
Terminal Input Output Connection to Voltage (After warming-up) Remarks Terminal Input Output Connection to IGN: ON Idle Remarks
1P — — — — —
1Q — — — — —
1R — — — — —
1S o Air bypass solenoid valve (Idle-up C) and P/S pressure switch
Battery voltage While solenoid ON (Refer to page 4B—35): below 1.5V
1T — — — — —
1U — — — — —
1V 0 MTX
Neutral and clutch switch
In-gear condition Clutch pedal depressed: battery voltage Clutch pedal released: below 1,5V
Neutral: constant battery voltage
1W O Test connector Test connector grounded: below 1,5V Test connector not grounded: battery voltage Green connector, 1-pin
1X — — — — —
2A o V ref 4.5—5.5V
2B 0 Air flow meter (Vc) 6-10V
2C — — Ground (E2) Approx. OV
2D o Oxygen sensor OV 0-1.OV • Cold engine: 0V at idle • After warming-up: Increase engine speed: 0.5—1.0V Deceleration: 0—0.4V
2E 0 Air flow meter (Vs) Approx. 1.7V Approx. 3—5V Increase engine speed:
voltage increases
2F — -— — —
2G 0 Throttle sensor Accelerator pedal released:
0.4—0.6 V
2H 0 Atmospheric pres-sure sensor At sea level: approx. 4.0V
21 0 Water thermo sensor 0.3—0.6 V Engine coolant temp. 20°C (68°F): approx. 2.5V
2J o Air flow meter (In-
take air thermo
sensor)
Approx. 2.3V at 20°C (68°F)
2K o Solenoid valve (Pres-
sure regulator
control)
For 120 sec. after ignition switch OFF - ON: below 1.5V
For 120 sec. after
starting: below 1.5V
Hot condition: Cool-ant temp, above 70°C (158°F) Intake air temp, above 10°C (50°F)
2K o Solenoid valve (Pres-
sure regulator
control)
Battery voltage Other conditions
2L — — — — —
2M — — —
4B-89

TROUBLESHOOTING GUIDE 4C
TROUBLESHOOTING GUIDE
This troubleshooting guide shows the malfunction numbers and the symptoms of various failures.
Perform troubleshooting as described below.
Input sensors and switches
Possible cause
Page
Symptom and No. CO
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Fault Indicated by SST
Code No. 02 03 05 *i 08 09 11 12 *2 15 • 2 17 *2 25 26 *2 27 *2 28 • 2 34 36 • 2 41
Hard start or won't start
(Cranks OK)
Engine stalls
Rough
Idle
During warm up
After warm up
During warm up
After warm up
High idle speed after warm up
Poor acceleration, hesita-tion or lack of power
TROUBLESHOOTING PROCEDURE
Note
Code No. Is to quickly determine which system or unit may be at fault by use of the SST. (Self-Diagnosis Checker 49 H018 9A1 or Digital Code Checker 49 G018 9A0 with Adaptor harness 49 9200 180)
1st: Check input sensors and output solenoid valves with the SST. (Refer to
page
AC—11.)

2nd: Check other switches with the SST. (Refer to page AC—25.)
3rd: Check the following items:
Electrical system
1) Battery condition 2) Fuses
Runs rough on deceleration
Afterburn in exhaust
system
9
10
Poor fuel consumption
Engine stalls or runs
rough after hot starting
11
12
Knocking
Fuel system
1) Fuel level
2) Fuel leakage 3) Fuel filter 4) Idle speed (with test connec-tor grounded)
Engine
1) Compression 2) Overheating
Ignition system 1) Ignition spark
2) Ignition timing (with test connec-tor grounded)
Intake air system 1) Air cleaner element 2) Vacuum or air leakage 3) Vacuum hose routing 4) Accelerator cable
Others 1) Clutch slippage
2) Brake dragging
Fails emission test 4th: Check Fuel and Emission Control Systems. (Refer to page 4C—10.)
*1..
*2„
.Leaded fuel
.Unleaded fuel
76G04C-009
4C—9

INTAKE AIR SYSTEM 4C
76G04C-054
76G04C-055
76G04C-056
Removal Note
Water hose
Before disconnecting the water hose, drain two liters
of engine coolant.
Delivery pipe assembly.
1. Separate the fuel return pipe from the delivery pipe
assembly.
2. Remove the delivery pipe assembly and the fuel
return pipe.
PARTS INSPECTION
Air Cleaner Element
1. Check the condition of the air cleaner element.
2. Blow out the dust with compressed air, if
necessary.
Caution
a) The air cleaner must be replaced at the in-
tervals outlined in the maintenance
schedule.
b) Never drive the vehicle without the air
cleaner element, otherwise, damage to the
air flow sensor (hot wire) will occur.
c) Never use an oil permeated air cleaner ele-
ment, otherwise, contamination of the hot
wire will occur.
4C—33

ISC SYSTEM 4C
COMPONENT DESCRIPTION
Component Function Remark
A/C switch Detects air conditioner operation; sends
signal to engine control unit Switch ON when air conditioner
operating
Air valve When cold, supplies bypass air into dy-namic chamber • Engine speed increased to shorten warm-up period • Thermo wax type
• Installed in BAC valve
Clutch switch Detects in-gear condition; sends signal to engine control unit Switch ON when clutch pedal released
E/L control unit Detects that E/L is being applied; sends
signal to engine control unit
Engine control unit Detects signals from input sensors and switches; controls solenoid valve (Idle speed control)
Idle switch Detects when throttle valve fully closed;
sends signal to engine control unit
Installed on throttle body
Ne signal pick-up Detects crank angle at 180° intervals; sends signal to engine control unit Installed in distributor
Neutral switch Detects in-gear condition; sends signal to engine control unit
Switch ON when in gear
P/S pressure switch Detects P/S operation; sends signal to engine control unit Switch ON when steering wheel turned right or left
Solenoid valve (Idle speed control) Controls bypass air amount • Controlled by duty signal from engine control unit • Installed in BAC valve
• Operates idle-up
Test connector For initial idle speed adjustment • Gerrn, 1-pin
• Idle speed feedback control cancelled when connector grounded
Water thermo sensor Detects coolant temperature; sends
signal to engine control unit
76G04C-078
4C—45

4C
ISC
SYSTEM
TROUBLESHOOTING
Check the condition of the wiring harness and connectors before checking the sensors or switches.
Note
Make the system inspection first. If no problem is found, continue with inspection of the
next system of the Troubleshooting Guide. (Refer to pages 4C—10 and 11.)
Possible cause
\Page
Symptom
Air valve P/S pres-sure switch
Solenoid
valve (Idle
speed
control)
Water
thermo
sensor
Engine control unit terminal System
In-
spection
Possible cause
\Page
Symptom
Air valve P/S pres-sure switch
Solenoid
valve (Idle
speed
control)
Water
thermo
sensor
1L 1W 2Q
System
In-
spection
Possible cause
\Page
Symptom 4C—47 4C—97 4C—48 4C—107 4C—98 4C—46
Engine
stalls
During warm up 2 — 3 4 — 5 6 1 Engine
stalls After warm up — 4 2 — 3 5 6 1
Rough
idle
During warm up 2 — 3 — — 4 5 1 Rough
idle After warm up 4 2 — 3 5 6 1
High idle speed after warm up 2 5 3 — 4 6 7 1
Runs rough on deceleration — — 2 — — 3 4 1
Afterburn in exhaust system 2 — 3 — — 4 5 1
Falls emission test 2 3 — — 4 5 1
76g04c-079
System Inspection
(Air valve)
1. Ground the test connector (Green, 1-pin) with a
jumper wire.
2. Disconnect the ISC valve connector (Gray, 2-pin)
at idle while the engine is cold.
3. Note the engine speed and reconnect the con-
nector.
4. Warm up the engine to the normal operating tem-
perature and disconnect the connector again.
5. Check that the engine speed is lower than that
when cold.
4C—46

ISC SYSTEM 4C
76G04C-081
76G04C-082
Cooling fan switch
Rear defroster switch
Head light switch
Blower motor switch
ISC "valve
76G04C-083
(ISC valve)
6. Connect the ISC valve connector.
Note
a) Make sure that the initial idle speed is set
to specification.
b) All accessory must be OFF.
7. Again disconnect the ISC valve connector (engine
at normal operating temperature).
8. Check that the engine speed decreases.
9. Reconnect the ISC valve connector.
10 Remove the jumper wire from the test connector
and make sure that the idle speed is within specifi-
cations.
(Load Test)
11. Apply power steering, electrical, and air conditioner
loads and check that the idle speed is controlled
to within specifications.
Load Idle speed
P/S 750 ± 50
E/L 800 ± 50
A/C 800 ± 50
E/L and A/C 800 ± 50
BAC Valve
Air valve
1. Remove the BAC valve from the throttle body.
2. Blow air through the valve from port A and check
that air comes out of port B when the BAC valve
is cold..
3. If not correct, replace the BAC valve.
Note
Refer to "Installation" on this page for the
BAC valve installation.
86U04A-063
4C—47

4C FUEL SYSTEM
COMPONENT DESCRIPTION
Component Function Remark
Air flow sensor Detects amount of intake air;
sends signal to engine control unit
Clutch switch Detects in-gear condition; sends signal to engine control unit Switch ON when clutch pedal released
Engine control unit Detects signals from input sensors and switches; controls injector and fuel pump operations
Fuel filter Filters fuel
Fuel pump Provides fuel to injectors • Operates while engine running
• Installed in fuel tank
Fuel pump control unit (4WS) Monitors fuel level in left section; controls transfer pump operation
G signal pick-up Detects No.1 cylinder TDC; sends signal to engine control unit Installed in distributor
Idle switch Detects when throttle valve fully closed; sends signal to engine control unit Installed on throttle body
Ignition switch (ST position) Sends engine cranking signal to engine control unit
Injector Injects fuel into intake port • Controlled by signals from engine control unit • High-ohmic injector
Intake air thermo sensor Detects intake air temperature; send signal to engine control unit
Control relay Supplies electric current to injectors fuel pump and engine control unit
Ne signal pick-up Detects crank angle at 180° intervals; sends signal to engine control unit Installed in distributor
Neutral switch Detects in-gear condition; sends signal to engine control unit
Switch ON when in gear
Oxygen sensor (Unleaded fuel) Detects oxygen concentration; sends signal to engine control unit
• Zirconia ceramic and platinum coating • Integrated heater coil
Pressure regulator Adjusts fuel pressure supplied to injectors
Pulsation damper Absorbs fuel pulsation
Throttle sensor Detects throttle valve opening angle;
sends signal to engine control unit
Installed on throttle body
Transfer pump (4WS) Pumps fuel from the left to the right side Controlled by fuel pump control unit
Transfer pump switch (4WS) Detects fuel level in left section;
sends signal to control unit
Water thermo sensor Detects coolant temperature; sends signal to engine control unit
Water thermo switch (Unleaded fuel) Detects radiator coolant temperature; sends signal to engine control unit ON: above 17°C (63°F)
76G04C-088
4C-50

4C PRC SYSTEM
PRESSURE REGULATOR CONTROL
(PRC)
SYSTEM
Distributor (Ne signal)
I Fuel
(To fuel tank)
76G04C-128
To prevent percolation of the fuel during idle after the engine is restarted, vacuum is cut to the pres-
sure regulator, increasing the fuel pressure.
Specified time: Approx. 120 sec.
Operating condition: Coolant temperature — above 70°C (158°F)
Intake air temperature — above 30°C (86°F)....Unleaded fuel
above 50°C (122°F)....Leaded fuel
4C-68