1991 FORD FESTIVA Service Manual

connector while moving vane in VAF meter. Voltage should be as specified in VAF METER VOLTAGE table. If voltage is okay,
repair VAF wire to ECA. If voltage is not okay, go to next step.
VAF METER VOLTAGE
4. Unplug connector from VAF. Using jumper wires, connect VPWR and SIGRTN terminals on VAF connector to corresponding terminals
on VAF meter. Leave VAF and VMREF wires disconnected. Measure voltage between VAF terminal at VAF meter, and SIGRTN pin at
harness connector while moving vane in VAF meter. Voltage should be as specified in VAF METER VOLTAGE
table. If voltage is
okay, repair VMREF wire to ECA. If voltage is not okay, go to next step.
5. Unplug connector from VAF meter. Turn ignition on. Measure voltage between SIGRTN and VPWR wire. If voltage is more than 10
volts, replace VAF meter. If voltage is not more than 10 volts, go to next step.
6. Unplug VAF meter connector. Turn ignition on. Measure voltage between VAF meter VPWR wire and ground. If voltage is more than
10 volts, repair VAF wire to ECA. If voltage is not more than 10 volts, go to PINPOINT TEST VPWR.
PINPOINT TEST ECT - ENGINE COOLANT TEMPERATURE SENSOR

Fig. 9: Identifying ECT Sensor Circuits

ECT CIRCUIT PIN IDENTIFICATION
1.3L
1. Turn ignition off. Install BOB. Leave ECA disconnected. Unplug ECT connector. Check for continuity between ECT test pin and ECT
terminal (Red/Blue wire) on ECT harness connector. If continuity does not exist, repair ECT wire between ECA and ECT sensor. If
continuity exists, go to next step.
2. Unplug ECT sensor. Check for continuity between Black wire at ECT sensor and ground. If continuity does not exist, repair Black wire
between ECT sensor and ground. If continuity exists, go to next step.
3. Reconnect ECA. Measure resistance between BOB ECT test pin and ground pin. If resistance is 500-1000 ohms, replace ECA. If
resistance is not 500-1000 ohms, replace ECT sensor.
1.6L
1. Turn ignition off. Install BOB. Leave ECA disconnected. Unplug ECT connector. Check for continuity between ECT test pin and ECT
terminal (Blue/Red wire) on ECT harness connector. If continuity does not exist, repair ECT wire between ECA and ECT sensor. If
Door PositionVolts
1/8 Open3.24
1/4 Open5.60
3/8 Open5.62
1/2 Open5.83
5/8 Open6.02
3/4 Open6.57
7/8 Open7.46
Full Open7.87
NOTE:Enter this test only when a Code 09 is displayed during QUICK T EST S procedure or when directed here
from another PINPOINT T EST . T o prevent unnecessary diagnosis, inspect coolant level, oil level,
cooling fan, therm ostat, and airflow to radiator before testing.
CircuitECA PinBOB PinWire Color
1.3L
ECT2Q7RED/BLU
GND(1) (1) BLK
1.6L
ECT2I7BLU/RED
SIGRTN2C46BLU/YEL
(1)Not specified.
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continuity exists, go to next step.
2. Install BOB. Connect ECT. Warm engine to normal operating temperature. Measure resistance between ECT test pin and SIGRTN pins.
If resistance is 500-1000 ohms, replace ECA. If resistance is not 500-1000 ohms, replace ECT sensor.
PINPOINT TEST VAT - VANE AIR TEMPERATURE SENSOR

Fig. 10: Identifying VAT Circuits

VAT CIRCUIT PIN IDENTIFICATION
1. Turn ignition off. Ensure engine is at operating temperature. With ignition off, install BOB. Turn ignition on. Measure temperature near
VAT sensor. Measure voltage between VAT and SIGRTN test pins. Compare voltage to specifications shown in VAT SENSOR
VOLTAGE table. If voltage is within specification, VAT circuit is okay. If voltage is not within specification, go to next step.
VAT SENSOR VOLTAGE
2. Turn ignition off. Disconnect ECA. Measure resistance between VAT and SIGRTN test pins. Measure temperature near VAF meter.
Compare resistance to specifications shown in VAT SENSOR RESISTANCE
table. If resistance is within specification, go to next
step. If resistance is not within specification, go to step 4).
3. Unplug VAF sensor connector. Measure resistance between VAT test pin and all other test pins. If any resistance is less than 5 ohms,
repair VAT wire from ECA to VAF meter. If all measurements are greater than 5 ohms, replace ECA.
4. Turn ignition off. Unplug VAF meter connector. Monitor temperature near VAT sensor. Measure resistance between VAF meter VAT
and SIGRTN terminals. Compare resistance to specifications shown in VAT SENSOR RESISTANCE
table while heating VAT sensor .
If resistance is within specification, repair VAT and/or SIGRTN wires from VAF to ECA. If resistance is not within specification, replace
VAF meter.
VAT SENSOR RESISTANCE NOTE:Enter this test only when a Code 10 is displayed during QUICK T EST S procedure or when directed here
from another PINPOINT T EST . Am bient tem perature m ust be higher than 50°F (10°C) for this test.
CircuitECA PinBOB PinWire Color
1.3L
GND2A46, 49BLK
VAT2P45GRN/BLK
1.6L
SIGRTN2C46,49BLU/YEL
VAT2J25BRN/YEL
Temperature °F (°C)(1) Volts
20 (-6)3.64
30 (-1)3.36
40 (4)3.05
44 (7)2.79
50 (10)2.29
60 (16)2.61
70 (21)2.35
80 (27)2.05
90 (32)1.76
100 (38)1.57
(1)Values may vary by 15 percent.
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PINPOINT TEST TP - THROTTLE POSITION SENSOR

Fig. 11: Identifying TP Circuits

TP CIRCUIT PIN IDENTIFICATION
1.6L
1. Turn ignition off. Install BOB. Turn ignition on. Measure voltage between BOB test pins TP and SIGRTN while opening throttle.
Compare voltage to specification in TP SENSOR OUTPUT VOLTAGE
table. Go to next step if output voltage is not within
specification.
TP SENSOR OUTPUT VOLTAGE
2. Turn ignition off. Unplug TP sensor connector at throttle body. Using jumper wires, connect VREF and SIGRTN wires on harness
Temperature °F (°C)Ohms
-4 (-23)15,000
32 (0)5210
68 (20)2500
104 (40)1100
140 (60)600
176 (80)300
NOTE:Enter this test only when a Code 12 is displayed during QUICK T EST S procedure or when directed here
from another PINPOINT TEST.
CircuitECA PinBOB PinWire Color
1.6L
IDL1E28GRN/ORG
SIGRTN2C46, 49BLK/YEL
TP2G47ORG
VREF2A26WHT/BLK
Throttle Opening(1) Voltage
1/81.00
1/41.60
3/82.37
1/22.74
5/83.15
3/43.43
7/83.60
(1)Voltage may vary by 15 percent.
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connector to corresponding terminals on TP sensor connector. Turn ignition on. Measure voltage between TP and SIGRTN terminals on
TP sensor while opening throttle. Compare voltage to specification in TP SENSOR OUTPUT VOLTAGE
table. If voltage is within
specification, repair TP wire to ECA. Go to next step if voltage is not within specification.
3. Turn ignition off. Unplug TP harness connector. Turn ignition on. Measure voltage between VREF and SIGRTN wires on TP harness
connect-or. If voltage is 4-5 volts, replace TP sensor. If voltage is not 4.5-5.5 volts, go to next step.
4. Measure voltage between VREF wire on TP harness connector and ground. If voltage is 4-5 volts, adjust or replace throttle position
sensor. If voltage is not 4-5 volts, go to PINPOINT TEST VREF
.
PINPOINT TEST BP - BAROMETRIC PRESSURE SENSOR

Fig. 12: Identifying BP Sensor Circuits

1.3L
BP sensor is incorporated into ECA; it cannot be checked or serviced separately. If Code 14 is set and cannot be cleared, replace ECA.
1.6L
Turn ignition off. Connect BOB. Remove dust cover from BP sensor, located on passenger side cowl. Turn ignition on. Connect vacuum pump
to BP sensor. Measure voltage between pins BP and SIGRTN on BOB while applying vacuum to BP sensor. See BAROMETRIC
PRESSURE SENSOR OUTPUT VOLTAGE table. Replace BP sensor if voltage is not as specified.
BAROMETRIC PRESSURE SENSOR OUTPUT VOLTAGE
PINPOINT TEST EGO - EXHAUST GAS OXYGEN SENSOR
EGO CIRCUIT PIN IDENTIFICATION
1. Warm engine to operating temperature, and let idle. Unplug EGO sensor. Measure voltage between EGO sensor connector (sensor side) NOTE:Enter this procedure only when a Code 14 is displayed during QUICK T EST S procedure or when
directed here from another PINPOINT T EST . T o prevent unnecessary replacem ent of com ponents, note
following non-EEC item s m ay be at fault: unusually high or low atm ospheric pressure, blocked vacuum
lines, or basic m echanical engine com ponents.
Vacuum (In. Hg.)(1) Voltage
03.84
53.36
102.66
151.93
201.26
25.58
(1)Voltage may vary by 15 percent.
NOTE:Enter this test only when a Code 15 (lean) or Code 17 (rich) is displayed during QUICK TESTS
procedure.
CircuitECA PinBOB PinWire Color
EGO
1.3L2N29BLU
1.6L2D29BLK
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and ground. With engine at idle, voltage should fluctuate between 0.2-0.8 volt.
2. Increase and decrease engine speed while reading voltmeter. When engine speed is decreasing, voltage should decrease. When engin e
speed is increasing, voltage should increase. If voltage is within specification, go to next step. If voltage is not within specification,
replace EGO sensor.
3. With ignition off, install BOB. Leave ECA disconnected. Unplug EGO sensor connector. Measure continuity between EGO test pin and
EGO sensor connector wire. If continuity exists, EGO circuit is okay; return to QUICK TESTS if sent here from there. If not sent here
from QUICK TESTS, replace ECA. If voltage is not as specified, repair VMREF wire to VAF. If continuity does not exist, service EGO
sensor wire to ECA.
PINPOINT TEST PRC - FUEL PRESSURE REGULATOR CONTROL SOLENOID

Fig. 13: Identifying PRC Circuit & Connector

PRC CIRCUIT PIN IDENTIFICATION
1. Locate Fuel Pressure Control (PRC) solenoid on cowl panel, next to canister purge solenoid. Unplug PRC solenoid connector. Remo ve
both vacuum lines. Plug vacuum port from engine vacuum source. Apply vacuum to remaining port. Replace PRC solenoid if it does not
hold vacuum.
2. Turn ignition off. Connect BOB. Leave ECA disconnected. Reconnect wiring to PRC solenoid. Turn ignition on. Apply vacuum to PRC
solenoid. Connect jumper wire between PRC test pin on BOB and ground. If vacuum drops to zero, PRC solenoid function is okay.
Return to QUICK TESTS if sent here from there. If vacuum does not drop to zero, go to next step.
3. Turn ignition off. Unplug PRC solenoid connector. Turn ignition on. Measure voltage between VPWR wire on harness connector and
gr o u n d . If vo l t a ge is n o t h igh e r t h a n 1 0 vo l t s, r e p a ir VP WR wir e t o ma in r e l a y. If vo l t a ge is h igh e r t h a n 1 0 vo l t s, go t o n e xt step.
4. Turn ignition off. Unplug PRC solenoid connector. Turn ignition on. Measure voltage between solenoid connector VPWR wire and
solenoid connector SIG wire. Connect jumper wire between PRC test pin on BOB and ground. If voltage is higher than 10 volts only
when solenoid is activated, replace solenoid. If voltage is not higher than 10 volts only when solenoid is activated, go to next step.
5. Turn ignition off. Connect BOB. Leave ECA disconnected. Unplug solenoid connector. Measure resistance between SIG test pin and
solenoid connector SIG wire. If resistance is not less than 5 ohms, repair SIG wire to ECA. If resistance is less than 5 ohms, go t o n e xt
step.
6. Turn ignition off. Connect BOB. Leave ECA disconnected. Unplug solenoid connector. Measure resistance between SIG test pin and all
other test pins. If resistance between SIG PRC test pin and any other pin is less than 5 ohms, repair PRC wire to ECA. If resistance
between PRC test pin and any other pin is greater than 10,000 ohms, replace ECA.
PINPOINT TEST CANP - CANISTER PURGE CONTROL SOLENOID
NOTE:Enter this test only when a Code 25 is displayed during QUICK T EST S procedure or when directed here
from another PINPOINT TEST.
CircuitECA PinBOB PinWire Color
PRC (1.6L)2K31BRN
NOTE:Enter this test only when a Code 26 is displayed during QUICK T EST S procedure or when directed here
from another PINPOINT TEST.
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Fig. 14: Identifying CANP Circuit & Connector
CANP CIRCUIT PIN IDENTIFICATION
1. Turn ignition off. Install BOB. Leave ECA disconnected. Turn ignition on. Remove canister purge hose from intake manifold, and apply
vacuum. Connect a jumper wire between CANP test terminal and ground. If vacuum releases, solenoid is okay. If vacuum does not
release, go to next step.
2. Locate CANP solenoid near center of cowl panel. Unplug solenoid connector. Apply vacuum to port from engine vacuum source.
Replace CANP solenoid if it does not hold vacuum.
3. Connect BOB. Leave ECA disconnected. Reconnect wiring to CANP solenoid. Turn ignition on. Apply vacuum to CANP solenoid.
Connect jumper wire between CANP test pin on BOB and ground. If vacuum drops to zero, solenoid function is okay. Return to QUIC
K
TESTS if sent here from there. If vacuum does not drop to zero, go to next step.
4. Turn ignition off. Unplug CANP solenoid connector. Turn ignition on. Measure voltage between VPWR wire on harness connector and
gr o u n d . If vo l t a ge is n o t h igh e r t h a n 1 0 vo l t s, r e p a ir VP WR wir e t o ma in r e l a y. If vo l t a ge is h igh e r t h a n 1 0 vo l t s, go t o n e xt step.
5. Turn ignition off. Unplug CANP solenoid connector. Turn ignition on. Measure voltage between solenoid connector VPWR wire and
solenoid connector SIG wire. Connect jumper wire between CANP test pin on BOB and ground. If voltage is higher than 10 volts only
when solenoid is activated, replace solenoid. If voltage is not higher than 10 volts only when solenoid is activated, go to next step.
6. Turn ignition off. Connect BOB. Leave ECA disconnected. Unplug CANP solenoid connector. Measure resistance between SIG test pin
and solenoid connector SIG wire. If resistance is not less than 5 ohms, repair SIG wire to ECA. If resistance is less than 5 ohms, go to
next step.
7. Turn ignition off. Connect BOB. Leave ECA disconnected. Unplug solenoid connector. Measure resistance between SIG test pin and all
other test pins. If resistance between SIG PRC test pin and any other pin is less than 5 ohms, repair CANP wire to ECA. If resistance
between CANP test pin and all other pins is greater than 10,000 ohms, replace ECA.
PINPOINT TEST ISC - IDLE SPEED CONTROL

Fig. 15: Identifying ISC Circuit & Connector

ISC CIRCUIT PIN IDENTIFICATION
1. Install BOB, leaving ECA disconnected. Turn ignition on. Connect a jumper between BOB test pin No. 41 and ground. Listen for
clicking sound from solenoid, mounted on throttle body. If clicking sound occurs, ISC solenoid is okay; return to QUICK TESTS if sen t
here from there. If no clicking sound occurs, go to next step.
2. Unplug ISC solenoid connector. With ignition on, measure voltage between VPWR wire and ground. If voltage is less than 10 volts,
repair VPWR wire to main relay. Go to next step if voltage is not less than 10 volts.
3. Measure voltage between ISC solenoid VPWR wire and solenoid connector SIG wire while cranking engine. Replace solenoid if voltage
is more than 10 volts only when engine is cranking. If okay, go to next step.
4. With BOB installed and ECA disconnected, unplug ISC solenoid connector. Check for continuity between BOB SIG test pin and ISC
connector SIG wire. If resistance is not less than 5 ohms, repair ISC wire between solenoid and ECA. If okay, go to next step.
5. With BOB installed and ECA disconnected, measure resistance between BOB SIG test pin and all other test pins. If resistance is less
than 5 ohms, repair short in SIC wire to ECA. If resistance is not less than 5 ohms, replace ECA.
PINPOINT TEST STI - SELF-TEST INPUT
STI CIRCUIT PIN IDENTIFICATION
CircuitECA PinBOB PinWire Color
CANP
1.3L2X31RED
1.6L2P32YEL
NOTE:Enter this test only when a Code 34 is displayed during QUICK T EST S procedure or when directed here
from another PINPOINT TEST.
CircuitECA PinBOB PinWire Color
ISC
1.3L2W41RED/BLK
1.6L2Q41GRN
NOTE:Enter this test only when sent here from QUICK TESTS.
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1. Turn ignition off. Install BOB. Leave ECA disconnected. Connect test light between STI test pin on BOB and 12-volt source. If test
light comes on, go to PINPOINT TEST STO
. If light does not come on, go to next step.
2. Leave test light connected. Ground STI connector. If test light does not come on, repair open circuit between STI connector and ECA.
PINPOINT TEST STO - SELF-TEST OUTPUT

Fig. 16: Identifying STI & STO Circuit & Connector

STO CIRCUIT PIN IDENTIFICATION
1. Turn ignition off. Install BOB. Leave ECA disconnected. Measure resistance between STO test pin and STO terminal of self-test
connector. If resistance is greater than 5 ohms, repair circuit between ECA and self-test connector. If resistance is less than 5 ohms, go
to next step.
2. Measure resistance between STO test pin and all other test pins. If resistance between STO test pin and any other test pin is less than 5
ohms, repair short in STO wire to diagnostic connector. If resistance is greater than 5 ohms, go to PINPOINT TEST PGC
.
PINPOINT TEST PGC - POWER & GROUND CONNECTIONS
PGC CIRCUIT PIN IDENTIFICATION
1. Turn ignition off. Install BOB, leaving ECA disconnected. Turn ignition on. Measure voltage at BOB pin in question. Compare voltage
to specification in PGC CIRCUIT PIN IDENTIFICATION
table. If voltage is not to specification, repair wire in question.
2. Measure resistance between ground and BOB pin in question. If any measurement is greater than 5 ohms, repair associated wire to
ground. If resistance is less than 5 ohms, return to PINPOINT TEST VREF
if sent here from there, and replace ECA. If not sent here
from PINPOINT TEST VREF, return to diagnostic routine.
PINPOINT TEST STG - SWITCH TO GROUND
CircuitECA PinBOB PinWire Color
STI
1.3L1K48YEL/GRN
1.6L1W48YEL
NOTE:Enter this test only when codes cannot be retrieved or when directed by PINPOINT T EST ST I.
CircuitECA PinBOB PinWire Color
STO
1.3L1F17YEL/WHT
1.6L1B17GRN/BLK
NOTE:Enter this test only when directed here from QUICK T EST S or another PINPOINT T EST .
CircuitECA PinBOB PinWire Color
1.3L
GND2A39, 40, 44, 60BLK
GND2B20BLK
GND2C16BLK
GND2D46, 49BLK
KAPWR1A1(1) WHT/RED
MT/AT (2) 2J6BLK
1.6L
GND2R49BLK
GND3A20BLK
GND3G40BLK
KAPWR3J1(1) BLU/RED
(1)Battery voltage.
(2)Manual transmission only.
NOTE:Enter this test only when directed here from QUICK T EST S or another PINPOINT T EST .
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STG CIRCUIT PIN IDENTIFICATION
1. Turn ignition off. Install BOB, leaving ECA disconnected. Measure resistance between switch BOB test pin and ground. Cycle switch. I
f
resistance is greater than 10,000 ohms with switch open and less than 5 ohms when switch is closed, switch is okay; go to step 4). If
resistance is not greater than 10,000 ohms with switch open, or greater than 5 ohms when switch is closed, go to next step.
2. Turn ignition off. Disconnect switch. Connect ohmmeter between switch terminals on 2-pin switches, or between ground and switch
ECA terminal on multi-pin or one-pin switches. Cycle switch. If resistance is not greater than 10,000 ohms with switch open, or is
greater than 5 ohms when switch is closed, replace switch. If resistance is greater than 10,000 ohms with switch open and less than 5
ohms when switch is closed, switch is okay; go to next step.
3. Turn ignition off. Install BOB, leaving ECA disconnected. Measure resistance between BOB pin for suspected switch and BOB pins 26,
37, 57, and 60. If any measurement is less than 10,000, repair shorted wire in question. If all measurements are greater than 10,000
ohms, go to next step.
4. Turn ignition off. Install BOB, leaving ECA disconnected. Measure resistance between BOB pin for suspected switch and switch
connector. If resistance is greater than 5 ohms, repair wire in question. If sent here from SWITCH MONITOR TEST in QUICK TESTS,
replace ECA; otherwise, return to QUICK TESTS.
PINPOINT TEST STP - SWITCH TO POWER
STP CIRCUIT PIN IDENTIFICATION
1. Turn ignition off. Install BOB, leaving ECA disconnected. Turn ignition on. Cycle switch in question. Measure voltage between switch
BOB test pin and ground. If voltage changes from less than 4 volts to more than 10 volts, switch is okay. If sent here from SWITCH
MONITOR TEST in QUICK TESTS, replace ECA. If sent here from elsewhere in QUICK TESTS, return to QUICK TESTS. If voltage is
not as specified, go to next step.
2. Turn ignition on. Measure voltage at switch in question on wire to ECA. Cycle switch. If voltage changes from less than 4 volts to more
than 10 volts, repair wire from switch to ECA. If voltage does not change from less than 4 volts to more than 10 volts, go to next step.
3. Turn ignition on. Install BOB, leaving ECA disconnected. Measure resistance between BOB test pin for switch in question and ground
and between BOB test pin and BOB pins 37, 57, and 26. If resistance is greater than 10,000 ohms for all measurements, go to next step.
If resistance is not greater than 10,000 ohms for all measurements, repair wire to switch.
4. Disconnect switch. Measure resistance between switch terminals. Cycle switch. If resistance is less than 5 ohms with switch closed and
greater than 10,000 ohms with switch open, switch is okay. If sent here from SWITCH MONITOR TEST in QUICK TESTS, return to
QUICK TESTS. If sent here from elsewhere in QUICK TESTS, replace ECA. If resistance is not as specified, replace switch.
PINPOINT TEST VPWR - VEHICLE POWER
SwitchECA PinBOB PinWire Color
1.3L
ACS1Q10BLU/RED
BLMT1S23GRN
IDL1N18YEL/BLK
NGS/CES (1) 1V43BLU/WHT
PSPS1P19PNK
WOT2L27YEL
1.6L
BPS (2) 2L12LT GRN/BLK
IDL1E18GRN/ORG
NGS/CES (1) 1G8RED/BLU
PSPS1K19GRN/RED
(1)Manual transmission only.
(2)Turbo only.
NOTE:For 1.3L, blower m otor resistor m ust be disconnected, HEAT ER fuse m ust be rem oved, and blower
m otor switch m ust be in position "1" when testing ACS signal.
NOTE:Enter this test only when directed here from QUICK T EST S.
SwitchECA PinBOB PinWire Color
1.3L
ACS1Q10GRN
BOO1O2GRN/RED
DEF1T30BLK/BLU
Fan1R22YEL/RED
HLDT1U28WHT
VST1C5BLK/RED
1.6L
BOO1J3WHT/GRN
VST3B5BLK/RED
NOTE:Enter this test only when directed here from another PINPOINT T EST . T o prevent replacem ent of good
com ponents, note following non-EEC com ponents m ay be faulty: ignition switch, alternator, battery
cables, ground straps, or voltage regulator. T his test is intended to diagnose only ECA, wiring harness
circuits, and battery voltage.
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