2014 WN cooling fans won't turn on

Discussion on Air Conditioning/Heat & electronic controls for the same, radiators/fans/engine cooling and related items.
Odyssey
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Re: 2014 WN cooling fans won't turn on

Post by Odyssey »

I found it, thank you for that. Very helpful pictures and info. Should be enough to keep me busy until the scope arrives. Goong to drive into the harness now
Pursuit
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Re: 2014 WN cooling fans won't turn on

Post by Pursuit »

Those pictures only show the Impala fix. I used that bulletin to fix my 2012 Impala cooling fan issue. There is a kit that you could buy, also.

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JoeR
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Re: 2014 WN cooling fans won't turn on

Post by JoeR »

I brought my own 2014 Caprice home today and while I had it in the shop I figured I'd see how that fan control circuit worked. Apparently it is controlled by a 12V pulse, not 5V. The module needs to see a particular frequency to control fan speed.
When the signal from the PCM is 12V (really battery voltage) the fan is off.
The longer the PCM pulses the signal to ground, the faster then fans run.
Ignore the really noisy 12V signal in these pics. I had a battery charger on there that leaked lots of AC voltage. It should be a steady signal and not the bumpy signal shown here.
Pic 1, Fans off. 12V to fan controller.
Pic 2, Fans full throttle. Mostly grounded signal to the controller.
Pic 3, Fans at about 50% duty cycle.
Pic 4, Fan at about 20% on.

Hope this helps you figure it out.

Joe
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Odyssey
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Re: 2014 WN cooling fans won't turn on

Post by Odyssey »

Thank you! That does help as I was not really sure what I was looking for (learning how to use the oscilloscope in my spare time).

I can use these as a control for what I should be seeing. Going in blind with a new tool, no idea what pulse or voltage I should be seeing, and on a malfunctioning system... I was chasing my tail. This will help for sure.
Odyssey
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Re: 2014 WN cooling fans won't turn on

Post by Odyssey »

Got a little free time and tried to track this down. On the oscilloscope and my multimeter that reads HZ% I'm seeing no signal on the small wire when I command the fans on or turn my AC on. I'm putting the red lead to the small black/white wire and my black lead to ground on the connector. Just want to make sure that's the right way to measure?

I tried tracing the small black/white wire and it went into a larger loom that disappeared under the fuse box. My guess is that wire goes back to the PCM. So I think my next step is to find what PIN it goes to on the PCM and see if it OHMs out to the connector. If I get continuitity I guess I'm left with a strange PCM issue. Does that make sense? Want to make sure I'm not missing something before buying a new PCM.

Not sure if this is related but while tracing the loom I saw this connector loose behind the passenger side headlight. Couldn't see any plug for it, might be unrelated but any idea what this is?
JoeR
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Re: 2014 WN cooling fans won't turn on

Post by JoeR »

A couple of things:
Don't connect the scope ground to anything related to the fan. That's the system you're diagnosing. It's good practice to find a different ground. Any other metal surface on the car will do.
Try scoping the MAF signal to see if the scope is working correctly. Backprobe the green wire with the white stripe at the MAF with the engine running. That signal is going to be WAY faster than the fan one, but it'll tell you if you're using the scope correctly.

The white wire with the black stripe to the fan module goes pack to pin 58 of Connector 1 at the PCM. It also goes through pin 39 of connector X126. X126 is the 40 pin connector that goes to the right forward lamp harness.

I agree that you need to do a continuity check on that wire. It is WAY more likely you have a wiring problem than a bad PCM.
to help you find the wire at the pcm, pin 57 is blank and pin 59 is yellow.

Joe
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rcg530
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Re: 2014 WN cooling fans won't turn on

Post by rcg530 »

One thing I just noticed in the wiring schematic that I placed in a post in this thread is that it shows connector X110 pin 34 as part of that circuit. The X110 connector is "Forward Lamp to Left Headlamp" and it only contains 10 pins. It looks like the X110 pin 34 should be X115 pin 34. Connector X115 is the "Engine Harness to Body Front Harness" connector

Wiring Schematic: (Cooling System Control Wire Portion)
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X126 Connector:
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X115 Connector:
2014_caprice_cooling_control_x115.png
2014_caprice_cooling_control_x115.png (199.37 KiB) Viewed 1615 times
2014 Chevy Caprice PPV | RetroCarGuy530 YouTube Channel
JoeR
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Re: 2014 WN cooling fans won't turn on

Post by JoeR »

Nice diagrams!
Odyssey
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Re: 2014 WN cooling fans won't turn on

Post by Odyssey »

I ran the test with my oscilloscope and was able to see wave lengths by backprobing the MAF sensor while engine running and using a ground lug in the engine bay. Good sanity check because that was the first time I'd seen my scope produce results.

I tried the fan connector again, this time using same ground lug I used for the MAF test. Still no movement on the scope when fans are commanded on. Tried a number of different settings on the scope but it was flatlined.

I pulled connector 1 on the PCM and checked continuitity between pin 58 and the small black/white wire on the connector. To my suprise it does have continuitity.

Just to rule out an issue with HPTuners fan controls, I left the car idle up to 235°F with the AC on and the fans did not turn on.

So now I'm really scratching my head as to what the problem could be.

Not to muddy the waters too much, but while tracing wires I noticed the female connector directly beside X126 is unplugged. Didn't see the male side of the connector anywhere. I've attached a picture, could this possible cause an issue with the fans?
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rcg530
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Re: 2014 WN cooling fans won't turn on

Post by rcg530 »

The smaller connector in your picture is number 4 in the diagram in my post and that's the "X100 Front Fascia Harness to Body Harness" connector.

It doesn't have any of the cooling system wiring running through it. It looks like it has wires for the parking lamps in the bumper fascia.
2014_caprice_x100.png
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