4-50 673831-Rev A
ELECTRICAL
4
Instrumentation Circuit
Symptom: Fan does not turn on.
Symptom: Engine oil pressure not detected.
Symptom: Engine oil pressure low with engine running.
Probable Cause Remedy
Engine temperature is below 150° F (66°
C).
The fan motor (M4) does not turn on until the engine temperature reaches 150° F (66° C)
Faulty 30-amp fuse (F5) Test 30-amp fuse (F5). (See “Fuse Test” on page 4-53.)
Faulty 10-amp fuse (F8) Test 10-amp fuse (F8). (See “Fuse Test” on page 4-53.)
Faulty temperature sender. Test the temperature sender (R5). (See “Engine Temperature Sender Test” on
page 4-62.)
Faulty fan relay. Test the fan relay (K4). (See “Relays Test” on page 4-53.)
Faulty fan motor Test the fan motor (M4). (See “Fan Motor Test” on page 4-61.)
Faulty wire harness Check continuity between MCU (U1) terminal 3-02 and the temperature sender (R5).
Continuity must be indicated.
Check continuity between temperature sender (R5) and coolant temperature resistor(R2).
Continuity must be indicated.
Check continuity between ignition relay (K1) terminal 87 and coolant temperature resistor
(R2). Continuity must be indicated.
Check continuity between ignition relay (K1) terminal 87 and 10-amp fuse (F8). Continuity
must be indicated.
Check continuity between 10-amp fuse (F8) and fan relay (K4) terminal 30. Continuity
must be indicated.
Check continuity between 30-amp fuse (F5) and fan motor (M4) terminal 1. Continuity
must be indicated.
Check continuity between MCU (U1) terminal 2-04 and fan relay(K4) terminal 86.
Continuity must be indicated.
Check continuity between fan relay (K4) terminal 87 and the fan motor (M4) terminal 3.
Continuity must be indicated.
Check continuity between ground and fan relay(K4) terminal 85. Continuity must be
indicated.
Check continuity between ground and fan motor (M4) terminals 2 and 4. Continuity must
be indicated.
Faulty MCU. Replace MCU
Probable Cause Remedy
Faulty engine oil pressure switch. With the key switch in the OFF position, check continuity between engine oil pressure
switch (SW11) and ground. Continuity must be indicated. If continuity is not indicated,
replace engine oil pressure switch.
Faulty engine oil pressure switch circuit. Check continuity between engine oil pressure switch (SW11) terminal and MCU (U1)
terminal 6-11. Continuity must be indicated.
Probable Cause Remedy
Low engine oil pressure. Check engine oil pressure.
Faulty engine oil pressure switch. If engine oil pressure tests good, replace engine oil pressure switch.
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