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George H.
George H., ASE Certified Technician
Category: Nissan
Satisfied Customers: 18538
Experience:  ASE Master 15+ years
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Need Fuse Box and Relay Diagram for Nissan Altima.

Resolved Question:

Need the diagram for the fuse and relay under the hood of a 03 Nissan Altima. None of the coiling fans are getting power nor the horn.

Submitted: 7 years ago.
Category: Nissan
Expert:  George H. replied 7 years ago.


For the cooling fans look to the two 40 amp fuses that provide power to the fans, if these are good you will have to check the ECM signal to the relays that turns the fans on. Try with the AC on and see if either fan starts


For the horn it is a different story,

Check the 15 amp horn fuse then check the horn relay to see if it has power, if it does the signal from the horn switch may not be reaching the relay due to a broken clockspring




Let me know where you are with this (what fuses have power, can you jump the #30 and #87 terminals of the relays and make the fans/horn function etc) and I will help you get to the bottom of the problem


Customer: replied 7 years ago.


How to jump terminals. By the way I'm using a fan motor from a 98 maxima.

Expert:  George H. replied 7 years ago.

You are using a test light to see if power is getting to the fan motor connection?

Do you have a check engine light on?

Lets start with the horn relay in the front of the IPM. To jump the relay pull the relay out of the socket in the IPM and use a paper clip to connect the two large copper colored terminal sockets. Use your testlight to find which has power and connect that one to the other large terminal socket next to that.

If you tried to install the wrong fan of the CPU in the IPM, it may be objecting to that. So I need to know if you have a check engine light on and if this vehicle has been damaged and that is why you are trying to use a fan from the wrong year.

Customer: replied 6 years ago.

Yes I'm using a test light.

Yes check engine light is on

I have a scan tool


H02S Bank 1 sen 1

Heater circuit low


H0S Bank 1 Sen 2

Heater circuit low

What is IPW and where is it?

Which one is the horn relay ?

The vehicle was damaged and I was not able to find the correct fan.The old fan had siezed up and the airbag was blown

Dont know much about auto electrical so please bear with me.

Expert:  George H. replied 6 years ago.

I am concerned as the IPM is the intelligent power module and it has a computer in it that is told by the engine computer what to do and tell the engine computer if it senses a fault in the systems that it controls.

If the IPM has a fault logged it may not turn the fans on.

So lets start with the horn as it is the easier circuit. If the vehicle was damaged and the airbag deployed the clockspring may have been damaged. This is the spirial connector that connects the airbag and hornswitch to the vehicle wiring harness.

Find the horn relay in the front of the IPM which is the fuse/relay box located at the front of the right side of the engine compartment. Use the diagram that I posted below to locate the relay


You will have to determine which of the terminals is powered with your testlight. I don't know the exact configuration of the pins on the relay so I see you tried to post a picture above?

If you did take a picture of the bottom of the relay and post it by using the tree icon in the tool bar of the posting window

Expert:  George H. replied 6 years ago.

In the diagram I posted above of the horn circuit, it shows the horn relay socket in the IPM. If you use your paperclip to jump from #1 to #3 and the horn sounds the fault is likely in the clockspring and we can move on to the cooling fans.

Let me know if you can get the horn to sound


Customer: replied 6 years ago.





Is this the right set-up. I'm getting power from # *****

Expert:  George H. replied 6 years ago.

If you look at the H1 diagram in the lower right of the horn wiring diagram, it lays out the position of the horn relay sockets. If you have power to #1 (top in the diagram) and use a paperclip to jump to #3, and the horns do not sound, then the problem is in the wiring to the horns or the horns itself. Leave the paperclip in and unplug a horn, use your testlight to see if there is power to the horn connector.

How badly was this car damaged?

Customer: replied 6 years ago.

Horn fixed. Both were dead. Replaced them and it worked.

Had to change right head light, hood, bumper cover bar, radiator support and a sensor on the condenser.

Is there a fuse for the cooling fans? The compass and the outside display on the rear-view mirror are also out.

Expert:  George H. replied 6 years ago.

The fans are fused with the large K and I fuses in the underhood panel. The sensor for the outside temp was likely damaged or is missing. It should be in front of the condenser in the grille as shown below


If you had to change all that check the power to the fuses and if that is good look for power to the relays, let me know if there is power available at the relay sockets

Customer: replied 6 years ago.

The temp sensor is fine. After I tried to install the fan the display for the outside temp and compass on the rear-view mirror went out.

This is where I'm getting power from the relays.


Expert:  George H. replied 6 years ago.

You will have to verify fan operation by connecting #9 to #5 to run one fan then #9 to #13 to run the other fan. If you haven't yet printed the fan wiring diagram, you can refer to it.

Once you are sure that the fans will run, you may need a scantool to see if the PCM is commanding the fans on or if a trouble code is set that would prevent fan operation. Use the connector diagram at the bottom of the wiring diagram to find the pin numbers that need to be jumped.

You are almost at the limit of what can be done without a scantool as the PCM communicates with the IPM through a communication bus that cannot be tested without a scantool that will read data.

Customer: replied 6 years ago.

I'm having problems matching up the diagram with the relay on the car.

Should I pull out relay 2 and 3 when connection #9 to #5?

Expert:  George H. replied 6 years ago.

You can have all the relays removed as you will be doing the job of the relay. All you want to do is connect the #9 white/blue wire to #5 red/yellow wire of the relay so that one of the fans will run. This will verify that the fan and the wiring is correct, then you connect the same #9 to #10 and the other fan should run. If they do, you are done and will need a scantool to command the relays on to verify that the computers are capable of turning the fans on. If you have a scan tool that will communicate with this vehicle and its modules, you can skip all this and just command the fans on.

Customer: replied 6 years ago.

Having problem matching this with the diagram. The ones in red are where I'm getting the power from. Can you help me with #9,#5,#13 and #10?


Expert:  George H. replied 6 years ago.

The large pins are the coils of the relays and the small pairs are contacts that are actuated by the coils so you want to jump the two on the left straight across. Do this one at a time

These are brown relays so you want to refer to the second diagram down in the set below


You can try this with the relay plugged in to test the systems and see if the fans will operate


  1. Close hood and lift wiper arms away from windshield (to prevent glass damage by wiper operation).
NOTE:When auto active test is performed with hood opened, sprinkle water on windshield beforehand.
  1. Turn ignition switch OFF.
  2. Turn ignition switch ON and, within 20 seconds , press front door switch LH ten times. Then turn ignition switch OFF.
CAUTION:Close front door RH.
  1. Turn ignition switch ON.
  2. When auto active test mode is actuated, horn chirps once, and oil pressure warning lamp starts blinking.
  3. After a series of operations is repeated three times, auto active test is completed.
NOTE:When auto active test mode has to be cancelled halfway, turn ignition switch OFF.


Customer: replied 6 years ago.

I got the fans to run.But I still cant find the fuse for the fans.
Is there a fuse for the a/c.Nothing is labelled under the hood.

Radiator fan was working before.I think when I was putting the fans back after installing the condenser fan the metal shield behind the radiator fan touched the alternator and sparked. May have short or burnt out something. I'm hopping Its the fuse because the display on the rear-view mirror for the outside temp and compass went out after this also. I had also just got the a/c gassed up.


Customer: replied 6 years ago.
Expert:  George H. replied 6 years ago.

With the power you measured at the fan relays the fuses should be good but the fuses are the K and I fuse shown in this diagram below. The legend is inside the fuse box lid

This is the one on the other side of the engine bay


You had all the relays installed and both fans worked on all speeds?

Customer: replied 6 years ago.
All relays were out when jumped it.graphic
Expert:  George H. replied 6 years ago.
When you tried the active test I posted above did the fans run?
Customer: replied 6 years ago.

Can't get active test to work.
I'm I to press lock or unlock?
Are the doors to be close?

Expert:  George H. replied 6 years ago.

The door switch is the light switch on the jamb of the door

The doors are open to start then when you turn the key to off you close the right door and turn the key on to do the rest of the procedure

Customer: replied 6 years ago.

Are all 4 doors to be open?

Expert:  George H. replied 6 years ago.

At least the front two

Customer: replied 6 years ago.
Nothing happend.
Expert:  George H. replied 6 years ago.
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