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
Posts: 29
Joined: Sat Sep 26, 2020 6:56 am

Re: 2014 WN cooling fans won't turn on

Post by Odyssey »

Very cool! Don't have a multimeter that reads hz but I'll put it on my list. Unfortunately it's looking more and more like an ECM problem. Just for a sanity check... with key on engine off the fans should turn on when I command them on via VCM Scanner right?
bstoner
Posts: 233
Joined: Wed May 05, 2021 2:12 pm

Re: 2014 WN cooling fans won't turn on

Post by bstoner »

Take the black/white wire connection on the fan control module (not the ECM wire side) and put it to ground. (This would be replicating the ECM telling the fan control module to run at 100% PWM.) You may have to jump the ground and power wire as well since the connector will be off. If fan turns on then the ECM is not sending the signal. If fans don't run the fan control module bad. Just do a couple taps to ground the wire. See if the fans start to spin up.

Another easy check is to unplug the temperature sensor in the driver side head. The ECM will command fans to run on high.
2014 Caprice PPV, 6.0L, BTR Stage 2 Cam, 3.45, 3" exhaust, Rotofab intake, Chris Henry tuned, future LSA....
Odyssey
Posts: 29
Joined: Sat Sep 26, 2020 6:56 am

Re: 2014 WN cooling fans won't turn on

Post by Odyssey »

Hmm, so when the smaller wire sees ground it completes the circuit and applies power to the fans and the PWM pulses ground on that smaller site to give the desired duty cycle?
JoeR
Posts: 150
Joined: Wed May 25, 2022 12:34 am
Location: Central, NC

Re: 2014 WN cooling fans won't turn on

Post by JoeR »

There is some related scanner data that you should check while you're commanding the fan on/off.
I believe it has:
Cooling Fan command
Cooling Fan Motor Command
Maybe Fan Speed too.

And not to state the obvious, but it doesn't have any fan codes in it, does it?

It would be great if you could get your hands on a scope. It would make quick work of the diagnosis. The most likely culprit at this point is the Fan Module, but it is too expensive of a part to guess at. If you had power, ground to the fan module, and a good PWM signal from the PCM it would condemn it, for sure.

Joe
Odyssey
Posts: 29
Joined: Sat Sep 26, 2020 6:56 am

Re: 2014 WN cooling fans won't turn on

Post by Odyssey »

In HPtuners scanner I see on/off commands for fan 1, fan 2, fan 3, fan speed (0%-100%), and ac clutch. I've tried all combinations as well as unplugging the coolant temp sensor but no luck.

My friend has a good fan control module in his caprice. I'll see if i can borrow it and plug it into my car. Should tell me if mine is bad or not. Really hope it's that simple, else I'll probably be looking at getting a scope or maybe a new ECM.
JoeR
Posts: 150
Joined: Wed May 25, 2022 12:34 am
Location: Central, NC

Re: 2014 WN cooling fans won't turn on

Post by JoeR »

Now that's interesting. The 2013 and older Caprices show having 3 fan relays to cycle with a scanner, but the 2014 shows only a module with 2 fans. I believe HP Tuners has it wrong for our cars. I just checked a Snap-on scanner, and for a 2013 Caprice it shows bi-directional controls for 3 relays. For the 2014 Caprice the Snap-on scanner shows a single fan control. If that's the case, then the fan control output from HP Tuners wouldn't be recognized by the PCM, and it would do nothing when you commanded a relay on.
Before doing anything else, get a different scanner on that thing to trigger the fans.

On edit: Please try the Fan-0-100% Functional Tests to see if that works before trying another scanner..

Joe
Odyssey
Posts: 29
Joined: Sat Sep 26, 2020 6:56 am

Re: 2014 WN cooling fans won't turn on

Post by Odyssey »

I tried changing the fan setting to 100% and turning it on but no luck. Also tried 50% and 80% just incase there was something weird with the 100% value. Also verified the ECM configuration had the fan mode set to 'PWM' instead of 'discrete' as was posted earlier. No DTC codes being thrown either.

I was able to borrow my buddies fan control module. It works in his '14 but not in mine. So far I've verified the following are good:
Power
Ground
Fan motors
Fan control module
Connectors and wires ohm out within spec so no open circuits

It's looking more and more like the ECM. I did order a $48 oscilloscope on Amazon. Going to give it a whirl before I bite the bullet and buy a new ECM. Such an odd problem, I would think if the fan PWM was faulty on the ECM I'd see other issues but this is the only problem so far.
JoeR
Posts: 150
Joined: Wed May 25, 2022 12:34 am
Location: Central, NC

Re: 2014 WN cooling fans won't turn on

Post by JoeR »

It's pretty rare to have a circuit driver in a GM pcm fail. It's going to be interesting to see what this ends up being.
Although GM doesn't state it, I'm betting the driver circuit will be 5V. Frequency will be fixed and Pulse Width will increase as you turn the fan speed up.
Joe
Odyssey
Posts: 29
Joined: Sat Sep 26, 2020 6:56 am

Re: 2014 WN cooling fans won't turn on

Post by Odyssey »

I was thinking this kind of ECM problem was rare too. Especially since nothing else appears to be wrong. Do you know where the fan module grounds? It ohms out to ground but wondering if maybe the ground is loose or corroded and had has problems when under load. Just trying to think of things to try until my oscilloscope arrives.
JoeR
Posts: 150
Joined: Wed May 25, 2022 12:34 am
Location: Central, NC

Re: 2014 WN cooling fans won't turn on

Post by JoeR »

Behind the Right Headlamp Assembly. It is G102.
There's an interesting service bulletin on these fans that shows a new harness and motor setup for them. I've got a pdf of it. PM me your email address and I can send a copy of it. Or you can google search for it if you want. It is special coverage adjustment 14588C
Joe
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