1988 JEEP CHEROKEE wiring

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Page 799 of 1378

JEEP CHEROKEE 1988 Service Repair Manual 2) Test resistance in wiring harness between ECU harn
terminal No. 32 and sensor connector terminal. Also test resistance
in wiring harness between ECU harness terminal No. 15 and sensor
conn

2) Test resistance in wiring harness between ECU harn
terminal No. 32 and sensor connector terminal. Also test resistance
in wiring harness between ECU harness terminal No. 15 and sensor
connector terminal. See Fig. 5. Repair wiring harness if open circuit
or resistance greater than one ohm is indicated.
TEMPERATURE-TO-RESISTANCE VALUES (CTS & MAT SENSOR) TABLE
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F C Ohms
(Approximate)
212 ......................... 100 ........................... 185
160 ......................... 70 ............................ 450
100 ......................... 38 ........................... 1600
70 .......................... 20 ........................... 3400
40 ........................... 4 ........................... 7500
20 .......................... -7 ......................... 13,500
0 ........................... -18 ........................ 25,000
-40 ......................... -40 ....................... 100,700
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Throttle Position Sensor (TPS) Test
Turn ignition on. Check voltage at terminal connector
without disconnecting from TPS. Terminal "A" (M/T), or terminal "B"
(A/T ) is output voltage, which should be 4.6-4.7 volts at wide open
throttle (M/T), or .2 volt at closed throttle (A/T). Terminal "B"
(M/T), or terminal "A" (A/T) is sensor ground. Terminal "C" (M/T),\
or
terminal "D" (A/T) is input voltage, which is about 5 volts.
Closed Throttle (Idle) Switch Test
NOTE: ALL testing of idle switch must be done with ISA motor
plunger in fully extended position. If switch cannot be
tested without extending plunger, it is possible that ISA
motor has failed. See IDLE SPEED ACTUATOR MOTOR ADJUSTMENT.
1) Turn ignition on. Check idle switch voltage at diagnostic
connector D2, between terminals No. 13 and 7. See Fig. 4. At closed
throttle, voltage should be near zero volts. When switch is off
closed throttle position, voltage reading should be greater than 2
volts.
2) If voltage is always zero, test for short to ground in
harness or switch. Also check for open circuit between switch and
terminal No. 25 of ECU connector. If reading is always greater than 2
volts, check for open circuit in wiring harness between switch
connector and ECU. Also check for open between ground and switch
connector. Replace or repair wiring harness as necessary.
Manifold Absolute Pressure (MAP) Sensor Test
1) Check and repair vacuum hose connections at throttle body
and MAP sensor. Check output voltage at MAP sensor connector terminal
"B" (marked on sensor body) with ignition on, engine off. Voltage
reading should be 4-5 volts. If engine is hot and idling in Neutral,
reading should be 1.5-2.1 volts. Check voltage at terminal No. 33 of
ECU connector. Reading should be same as that at terminal "B" on MAP
sensor connector. See Fig. 4.
2) With ignition on, check MAP sensor supply voltage at
terminal "C". Reading should be 4.5-5.5 volts. Same voltage reading
should be obtained at terminal No. 16 on ECU harness connector. If
necessary, repair or replace wiring harness. Using Diagnostic Tester
(MS 1700), test ECU if necessary. Check MAP sensor ground circuit at
terminal "A" and terminal No. 17 of ECU connector. Repair wiring if
necessary.