Mechanics

OVERHEATING

2003 Nissan Altima • 4 cylinder 2WD Automatic •

2003 Nissan Altima, Radiator fans don't come on and engine overheats. What sensor drives the fans?
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Bikerbill34
December 20, 2010.



It's the engine coolant temp sensor.


Saturntech9
Dec 20, 2010.
That's controlled by something called an "Intelligent Power distribution Module" which is controlled by the ECM after referencing the coolant temp sensor. There are (2) 40 amp fuses to check also.


Wrenchtech
Dec 21, 2010.
I've checked the fuses, and all 3 fan relays check good. The coolant temp sensor was replaced, so its new. I'm kinda stuck, don't know anything about these japanese cars.


Tiny
Bikerbill34
Dec 21, 2010.
Will any fans come on with the A/C?


Wrenchtech
Dec 21, 2010.
The only fan that comes on with the a/c is the blower. I bypassed the fan relays and can make both fans come on. However the relays check good. I've got good voltage to the coil side of all three relays, however there is no ground. Im guess ing this is how the ECM controls fan speed, by switching the ground? I'm so lost, LOL


Tiny
Bikerbill34
Dec 23, 2010.
Yes, the ground is the control trigger. You have no way to test that module though.


Wrenchtech
Dec 23, 2010.