1992 MAZDA PROTEGE sensor

DECHOKE CONTROL SYSTEM t-
DECHOKE CONTROL SYSTEM
DESCRIPTION
To facilitate starting the engine when the spark plugs become fouled, such as when the engine is flooded,
fuel injection is cut if the throttle valve is held wide open while cranking and the engine coolant temperature
is O°C (32OF) or below. This allows the spark oluas to drv and purges excess fuel from the cylinders.
f-- ECU _
. IGNITION SWITCH (START)
l ENGINE SPEED BELOW 500 rpm ’
l THROTTLE VALVE FULLY OPEN
l ENGINE COOLANT TEMPERATURE ;
BELOW
0% (32°F) I FUEL CUT
OBUOFX-19
I / / ‘ I
SYSTEM OPERATION
1.
2. Check if the engine coolant temperature is below O°C
(32OF).
If the engine coolant temperature is above O°C (32OF), dis-
connect the water thermosensor connector and connect an
approx. 10 kB resistor to the connector.
03UOFX.198 3. Turn the ignition switch to START and verify that the injec-
OBUOFX-19! 3
tor operating sound is heard.
4. Depress the accelerator pedal fully and turn the ignition
switch START. Verify that no injector operating sound is
heard.
F-l 45

CONTROL SYSTEM F
CONTROLSYSTEM
PREPARATION
SST
49 9200 162
Engine Signal
Monitor
49 HO18 9Al
Self-Diagnosis
Checker
49 GO1 8 904
Sheet For
inspection of
ECU
For
inspection of
oxygen sensor
For
inspection of
ECU 49 GO18 903
Adapter
harness
49 BO19 9AO
System
Selector For
inspection of
ECU
For
inspection of
oxygen sensor
03UOFX-20
F-l 47

F CONTROL SYSTEM
STRUCTURAL VIEW
23UOFX-1:
1. Engine control unit (ECU) 8. Solenoid valve (Pressure regulator control)
- .--
Removal / Installation . . . . . . . . . . . . . . . . page F-149
Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page F-149
2. Circuit opening relay
Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . page F-l 29
Inspection ,...,........................... page F-l 29
3. Clutch switch (MTX)
inspection . . . . . . . . . . . . . . . . . . . . . . . . . page F-l 72
4. Airflow meter (With intake air thermosensor)
Inspection .,..........,...,............... page F-l 68
5. ISC valve
Inspection .,*,........,.,.........,....... page F-116
Removal / Installation . . . . . . . . ,.... page F-l 09
G-Throttle sensor
Inspection . . . . . . . . . . . . , . . . . . . page F- 169
Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . page F-l 09
7. Solenoid valve (VICS) [DOHC]
Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page F-l 18 Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9. Water thermosensor
Inspection. . . . . . . .
Removal I Installation ....I..........
10. Solenoid valve(Purge control)
Inspection ,............ ,..................
11, Main relay (FUEL INJ relay)
Inspection. ..,............................
12. Neutral switch (MTX)
Inspection ,.,,,,....I.l,,.........I.......
Replacement . . . . . . .
13. Oxygen sensor
Inspection,. . . .
Replacement . , . . . .
14. P/S pressure switch
Inspection . . ..__.._._._........
Replacement . , . . . . . . . . . . . . . page t-135
page F-l 68
page F--l 68
page F-l 40
page F-172
page F-l 73
page F-173
page F-171
page F-172
--
page F-173
page F-173
F-l 48

F CONTROL SYSTEM
VB: Battery voltage
erminal Input Output Connection to Test condition Corrsct voltage Remark
1M - - - - - -
IN 0 Throttle sensor Accelerator pedal released ov Ignition switch
(Idle switch)
Accelerator pedal depressed
VB ON
10 0
1P 0 Stoplight switch
P/S pressure
switch Brake pedal released
Brake pedal depressed
Ignition switch ON
P/S ON at idle
P/S OFF at idle ov
-
VEi
Va
ov
VS -
10 0 A/C switch A/C switch ON
A/C switch OFF Below 23 Ignition switch
VS ON and blower
motor ON
1R 0
IS 0 Fan switch
Blower control
switch Fan operating (Engine coolant tempera-
ture over 97% (207OF) or diagnosis con-
nector terminal TFA grounded)
Fan not operating (Idle)
Blower control switch OFF or 1st position
Blower control switch 2nd or higher po-
sition ov
-
V0
Ve ignition switch
ov ON
IT 0 Rear window
defroster switch Rear window defroster switch OFF
Rear window defroster switch ON ov
VB
Ignition switch ON
1u 0
iv 0 Headlight switch
Neutral/Clutch
switches Headlights ON
Headlights OFF
Neutral position or clutch pedal
depressed
Others V0
-
ov
ov
VB -
1 I lr----t
r-i
ul r
2Y 2w 2u 2s 20 20 2M 2K 21 2G 2E 2’3 2A 1lJ 1s IQ 10 1M 1K 11 1G 1E 1~ 1A
22 2x 2v 2T 2R 2P 2N 2L 2J 34 2t= 2D 28 Ii/ fT 1R 1p IN 1L 1J 1H 1F 1D 18
F-l 52

CONTROL SYSTEM F
Ve: Battery voltage
Incorrect voltage
1, -
Always below l.OV
Always Ve
Always below I.OV (Stoplight OK)
Always below l.OV
Always
VB
Always below 25V (Blower fan OK)
Always
VB (Blower fan OK)
Always below 1 .OV
(Electrical cooling fan OK)
Always below 1 .OV (Blower fan OK)
Always
VB (Blower fan OK)
Always below
1 .ov
Always below l.OV Illumination lamp
ON when rear
window defroster
switch ON
Illumination lamp
never ON
(Headlights OK)
Always below l.OV
Always Ve Possible cause
-
l Throttle sensor misadjustment (Refer to page F-169)
l Short circuit in wiring from throttle sensor to ECU terminal 1N l ECU malfunction
l Throttle sensor misadjustment (Refer to page F-169) l Open circuit in wiring from throttle sensor to ECU terminal IN l Open circuit in wiring from throttle sensor to ECU terminal 2D
l Open circuit in wiring from stoplight switch to ECU terminal 10
l P/S pressure switch malfunction (Refer to page F-173) l Short circuit in wiring from P/S pressure switch to ECU terminal 1P l ECU malfunction
l P/S pressure switch malfunction (Refer to page F-173) l Open circuit in wiring from P/S pressure switch to ECU terminal 1P l Open circuit in wiring from P/S pressure switch to ground
l A/C switch malfunction (Refer to page U-55) l Short circuit in wiring from A/C switch to ECU terminal 10 l Poor connection at ECU connector l ECU malfunction
l A/C switch malfunction (Refer to page U-55) l Open circuit in wiring from A/C switch to ECU terminal 1Q l Open circuit in wirina from A/C switch to blower control switch
l Open or short circuit in wiring from fan relay to ECU terminal 1R l ECU malfunction
l Short circuit in wiring from blower control switch to ECU terminal 1s l Poor connection at ECU connector l ECU malfunction
l Open circuit in wiring from blower control switch to ECU terminal IS
I
l Open or short circuit in wiring from rear window defroster switch to ECU
terminal 1 T
l Open circuit in wiring from ignition switch to rear window defroster switch l Rear window defroster switch malfunction (Refer to page T-21)
l Open or short circuit in wiring from headlight relay to ECU terminal 1U
(Refer to page F-152)
l Neutral switch malfunction (Refer to page F-173) l Clutch switch malfunction (Refer to page F-172) l Short circuit in wirino from ECU terminal IV to neutral or clutch switch
l Neutral switch malfunction (Refer to page F-173) l Clutch switch malfunction (Refer to page F-172) l Open circuit in wiring from ECU terminal 1V to neutral or clutch switch l Poor connection at ECU connector
23UOFX-136
F-l 53

CONTROL SYSTEM
Ve: Battery
arminal Input Output Connection to lest condition Correct voltage Remark
2A - - Ground (Injector) Constant ov -
28 - - Ground (Output) Constant ov -
2c - - Ground (CPU) Constant ov -
2D - - Ground (Input) Constant ov -
2E 0 Distributor Ignition switch ON
Approx. OV
(Ne-signal) or 4.5-5.5V -
Idle Approx. 2V
2F - - - - - -
2G 0 Distributor Ignition switch ON Approx. OV
(G-signal) [DOHC] or 4.5-5.5V
Idle Approx. 1.5V
2H 0 Ground (California) Constant ov
-
Main relay Ignition switch ON Va
(Canada)
21 - - - - - -
2J 0 Open Constant Approx. l-29 -
2K 0 Throttle sensor Constant 4.5-5.5v
(ATX)/Airflow meter
-
2L 0 Throttle sensor
(Power switch) Accelerator pedal released
Accelerator pedal fully depressed Approx. 4.5~5%
ov -
2M 0 Throttle sensor Accelerator pedal released
Accelerator pedal fully depressed Approx. 0.5V
Approx. 4.OV -
2N 0 Oxygen sensor Ignition switch ON ov
Idle (Cold engine) ov
Idle (After warm-up) O-l .ov -
Increasing engine speed (After warm-up) 0.5-I .ov
Deceleration o-0.4v
20 0 Airflow meter Ignition switch ON Approx. 3.8V
-
Idle Approx. 3.3V
2P 0 Intake air ther- Ambient air temperature 20% (68OF) Approx. 2.5V Built in airflow
mosensor meter
2Q 0 Water thermo- Engine coolant temperature 20% (68’F) Approx. 29
_
sensor
After warm-up Below 0.5V
2R - - - - -
- 711 ICIFX-12 voltage
_““_. ,. .I 7
1 r u-
r-i Ll r
2Y 2w 2u 2s 20 20 2M 2K 21 2G 2E 2~2 2A 1U 1s 1Q 10 lft,j ,K ,, ,G ,E ,c ,A
22 2x 2v 2T 2R 2P 2N 2L 2J 2H 2F 2D 28
IV 1T fR 1p 1N 1L 1J ,H IF ID ,B
F-l 54

CONTROL SYSTEM
Ve: Battery voltage
Incorrect voltage
I Possible cause
4bove OV
l Poor contact at ground terminal l Open circuit in wiring from ECU to ground
Always approx. OV or approx. 2V
l Refer to Code No.02 Troubleshooting (Refer to page F-86) -
r\lways approx. OV or approx. 1.W - l Refer to Code No.03 Troubleshooting (Refer to page F-88)
Approx. 4.5-5.5V (California)
Always OV (Canada)
l Open circuit in wiring from ECU terminal 2H to ground
l Short circuit in wiring from ECU terminal 2l-i to main relay (FUEL INJ relay) - -
Approx. 4.5--55V l ECU malfunction
Always OV
l Short circuit in wiring from ECU terminal 2K to throttle sensor, or airflow
meter
Below 4.5V or above 5.5V
l Poor connection at ECU connector l ECU malfunction
1
l ECU malfunction
Always OV
l Throttle sensor malfunction (Refer to page F-169) l Short circuit in wiring from ECU terminal 2L to throttle sensor l Poor connectron at ECU connector l ECU malfunction
Always 4.5--5.W
Always constant
l Throttle sensor misadjustment (Refer to page F-169) l Open circuit in wiring from ECU terminal 2L to throttle sensor l Open circuit in wiring from ECU terminal 2L to ECU terminal 2D
l Open circuit in wiring from ECU terminal 2M to throttle sensor
l Open circuit in wiring from ECU terminal 2K to throttle sensor l Open circuit in wiring from ECU terminal 20 to throttle sensor
Always above 1V 1
l Throttle sensor misadjustment
OV after warm-up
Always approx. 1V after warm-up (
l Refer to Code No.15 Troubleshooting (Refer to page F-98)
I * Refer to Code No.1 7 Troubleshooting (Refer to page F-100)
Always OV or 4.5-5.5V
Always OV or 4.5~-5.W
I l
Refer to Code No.08 Troubleshooting (Refer to page F-90) l
Refer to Code No.10 Troubleshootrng (Refer to page F-94)
Always OV or 4.5-5.W l
Refer to Code No.09 Troubleshooting (Refer to page F-92) -
23UOFX-131
F-l 55

CONTROL SYSTEM
VB: Battery voltage
erminal Input Output
Connection to Test condition Correct voltage
Remark
1L
0 A/C relay Ignition switch ON VB
A/C switch ON at idle Below 2.5V
A/C switch OFF at idle V0
-
1M 0
1N 0 Vehicle speed
sensor
P/S pressure
switch While driving 4--5v
Vehicle stopped 0 or 8V
Ignition switch ON
VB
P/S ON at idle
ov
P/S OFF at idle Vi3 -
-
10 0 A/C switch A/C switch ON
A/C switch OFF Below 2.5V ignition switch
VB ON and blower
motor ON
IP 0 Blower control
switch Blower control switch OFF or 1st position Ve ignition switch
Blower control switch 2nd or higher po- Below 1 .OV ON
sition
1Q 0
1R 0
1s 0
IT 0 Stoplight switch Brake pedal released Below 1 .OV
-
Brake pedal depressed VI3
Inhibitor switch N or P range ov Ignition switch
(P, N ranges) ON
Other range VI3
Cruise control main Normal condition
VB Ignition switch
switch ON
Set or Resume switch ON or vehicle speed Below 1 .OV
8 km/h (5 mph) lower than preset speed
(Driving vehicle cruise control operation)
Throttle sensor Accelerator pedal released Below 1 .OV Ignition switch
(Idle switch)
Accelerator pedal depressed V0 ON
1u - - -
- - -
1v - - - -
- -
2A 0 Distributor Ignition switch ON Approx. OV
(Ne-signal) or 5V -
Idle Approx. 2V
LY”“l I. A3 311 blFY.1.
J
- .*
F-160