Overheating issue due to no fans running

Take a look at the wiring diagram. When you say you jumped pin 1 and 2 and the fan came on, I assume you mean of the radiator fan relay?

Also, when you turn on the A/C does your condenser fan come on at all?

These are only connect or related through the PCM. Basically the PCM grounds both relays to turn the fans on. So we need to turn them all on and test the wiring coming from the PCM. I suspect you don't have power on that wire. Which means either the PCM is not functioning or something is telling the PCM that the fans are not needed. This is why we need to confirm that neither fan is working with the A/C on. This would point away from an ECT issue.

Let us know what you find with this info and we can go from there. Thanks

When I turn on the A/C, no fans turn on. When I tested the relay outlet for the radiator fan, pin 1 had power. Pin 2 goes to the fan and runs when I jumper pin 1. Pin 3 has power when key is in the on position. Fan runs when pins 2 and 3 are jumped. Pin 4 no power.

The relay with the A/C and radiator symbols on it, all I have done is jumped pins 1 and 2 to rule out that the fans do work.

How do I go about testing the PCM?

Sounds like you already did. However, the way to confirm this is to test to see if the PCM can ground a 12 volt circuit. Remove the relay and put your negative meter lead on the 4 terminal. Then put the red lead on the positive post of the battery for the 12 volt source. Then turn the engine on and AC on so that both fans will come on. You meter should read 12 volts if the PCM is able to ground the circuit. If not, then PCM is suspect.

Take a look at the wiring diagram.

There’s three relays. Radiator fan, A/C fan, and a radiator and A/C fan relay. Which one should I be checking?

So, with checking just the A/C relay slot, with pin 4, positive on the battery, and negative on the pin.. I am getting no reading. Ignition is in the on position with A/C on. I can hear the blower fan going. No cooling fans are running.

You are correct that you have 3 relays. However, the PCM only actually grounds two of the relays because the Fan Control relay and the AC condenser relay control sides are tied together on the same circuit from the PCM. The third wire coming from the PCM (First wiring diagram with the black arrows) is to ground the PGM relay.

To address what you are seeing with not having voltage on pin 4 of the AC fan relay we need to look at the second wiring diagram.

The power starts at where I added number 1. We need to check fuse 11 to make sure you have power there. Then follow power down to number 2. The PCM grounds this relay on terminal 3 of the PGM relay. When this is grounded, the relay closes and power goes from terminal 1 of the relay to terminal number 2 of the relay (where I added number 3). It then goes to fuse 15 and then through the diode finally to number 4 that I added (also terminal 4 of the AC relay) which is where you are not getting power.

So you need to go backwards through this circuit to find where you have power and where you do not.

Let me know if you have questions. Thanks

I am sorry. I think I misread this. You need to put your red lead on the terminal number 4 of the A/C relay and the black lead of the meter on ground. Let me know what the voltage is with the engine running and A/C on.

I have power.

A/C on, ignition in the on position, no fans are on though, but I do hear the blower motor running. Positive on pin 4 of A/C only relay socket, negative on battery, I have connectivity.

Okay. Based on this it appears the PCM is the issue. It appears you have proven out the sensors and relays so if the fans are not coming on then I suspect the PCM is not grounding the relays.

Let's try to prove this out. Remove each of these relays that I am pointing to in this diagram and then put your red lead of your meter on the battery positive lead and then put the black lead on the relay terminal the arrow is pointing at one at a time and turn the engine on and A/C on. You should have 12 volts on the meter.

The pin configuration isn’t in the same order as what I am looking at.

Which one would be pin 3?

I attached the pin out for the fan control relay. Just test this one and we can go from there.

After you do that, let me know what you get with this info as well. Turn the key on and remove the relay. Test voltage between number 5 and ground (diagram 1 shows this test). Did you get 12 volts? If not, replace the relay box.

If you did get 12 volts check continuity between number 2 and ground (second diagram shows this test). Let me know what you get with these and we can figure this out. Thanks

First two tests, positive on the battery, negative on radiator fan relay pin 4: nothing

Negative on fan relay pin 3: nothing.

Tests 3 and 4, black lead on battery ground.

Positive lead on fan relay pin 2: no voltage.

Positive lead on fan relay pin 5: I have continuity.

Okay. Let's try these tests. I am thinking you have an issue on the relay box but this will tell us for sure.

With ignition in on position, positive lead on pin 5, negative lead on battery, I get continuity.

With positive lead on pin 2, negative on battery, I do not get anything.

Okay. Do you have your meter set to voltage or ohms? We need to have it set to voltage and let me know what the number is. You should have battery voltage which would be 12 volts or higher.

Continuity means the wire from pin to pin is intact and not an open circuit. We need to know what the voltage is. Thanks

Sorry, I meant voltage. Voltage is at 12v on Pin 5. Pin 2 doesn’t not read anything.

Okay. Now on the second measurement, we need to actually check for continuity (ohms) from Pin 2 to ground. If you have OL or an open circuit on your meter then that is the issue. We need to go to ground G301 and make sure it is good and tight. Then if it is, remove it and ohm out the wire from pin 2 to the connection of the ground wire. I suspect you will have an open circuit if the ground was tight.

I attached the location of G301. Let me know what questions you have. Thanks

This is the reading I got. Doesn’t seem to matter which setting I use. X1, x10, or x1K.

Everything looked fine with the ground wire. It has many wires that fit into one ring mount fitting to the frame. I cleaned and sanded the frame area where the ground mounts, and cleaned and sanded the connector mount, and re-connected it.

I re-tested with the ignition on, for voltage. Positive lead on positive battery, negative lead on pin 2 of fan relay. I have a voltage reading.

Okay. Based on those resistance readings you have 5 ohms of resistance from terminal 2 to ground. That means on the attachment, you performed the highlighted step and the result would be what I circled in red. That means we need to check for an open wire from this connector terminal 3 to the PCM or a connection issue if the wire is not broken or grounded.

Does that make sense?

What pin is on the PCM side that I am looking for? Could I do a continuity test from pin 3 of the blower fan relay to that particular pin that goes to the PCM to determine if the wire is okay, broken or grounding out?

I attached the diagram from the relay to the PCM. Yes, you can do a continuity test on that wire from end to end however, just understand that will only test the wiring and not the connection/terminal ends. So if there is a spread terminal you can have an open circuit. If the wire is okay, then it is surely a terminal issue.

Wait, I think I have to test the 5 pin blower fan relay again at pin 2 for ground again. I didn’t isolate the wire from the rest that share that ground. It has a spread connector where various wires connect to for grounding. It’s like a washer with a bunch of wires connected to it in a half circle.

When I took that ohm reading, I just disconnected that entire ring that all the wires are attached to from the frame.

Okay, yes. If I understand that correctly and you had the ground off and tested from pin 2 to ground then it would be open. I agree to retest it and let me know what you find.

Okay, I did an ohm test on pin two again, this time with the wire connected to the frame, and I get the same reading as before.

So if you have 5 ohms then you have continuity. That sounds high to me but it says to just check continuity and you have it. This means your issue according to the test, is from the number 3 terminal to the PCM or its terminals. See the attached.

So, I’ll go ahead and test pin 3 to PCM, and see if I can find something. Am I looking for a break in the line? Or a short?

All of the above. So test for short to ground, power and an open circuit.

Do you have a better diagram for locating that A5 pin on the PCM plug? I’ve been trying to track it down, and I am having a problem finding it. I think it would be easier for me to trace it back from the plug.

I attached the connector view. Let me know if you still need help and we can find some more detail but this should help find it.

I took a hard look around and I don’t see anything where the wire has been cut, or squished. I got continuity between pin 3 and pin 5 from the PCM. When I do an ohm reading, I get this:

Also, what test can I do to confirm if the problem still exists or not?

Also, another thought that I had. Is it possible to ground out the fans from the PCM connector to see if the fans kick on to determine if it’s the circuit or the PCM?

Just to confirm you were on pin 3 of the fan and 5 of the PCM and that is the resistance reading you got? If so, that wire is your problem. That appears to have more then 20 ohms of resistance. You should have less then .5 ohms. Basically with that meter if you have less then 1 ohm then your meter will look like it is on 0 so you switch to a higher setting. Then you need to do the math to get the reading but you have this on 1X showing more then 20 ohms so that is no math required and you just have slightly more then 20 ohms.

I would run a new wire from those two connectors and I bet you will fix the issue.

Okay, I will try that. Is there some sort of simple test that I can do to determine if the problem is resolved or not?

Unfortunately the test to determine if it is fixed or not is do operate the vehicle and it doesn't have the issue any longer. However, if you repair that and then do the same test and get a correct reading, you can be pretty confident that it is fixed.

Okay.so, I re-ran a wire from that #3 pin of the relay to the #5 pin of the black/white plug that connects to the PCM, and now I have 5 ohms.

Ran it like you said, and still the same problem. Cooling fans, neither one, come on.

I think the problem lies in the issue of not being able to jumper the coolant temperature switch that is located on the engine to turn the fan on.