Hood open message. Latch and BCM replaced.

[j91z28d1]

a volt meter can read voltage where there's practically none since they are designed to add no load to the circuit while testing very low load circuits. it can easily be reading a pull up resist on the circuit board in the bcm. or some other phantom voltage. but if you used say a test light that has to light a bulb you'd see nothing. you're probably seeing how the internal circuit is designed so that it sees the ground signal.


the quick and dirty test would be ground the pin at the bcm for hood closed and see if the dash warning goes away.

I haven't looked at this wiring diagram, but looking at mine that might be a little different. they wired the switch so that it knows if the hood is open, closed of if the switch is bad. that's why it's not a single one wire open/closed switch

 

[Fless]

I have no voltage at neither the purple (hood closed) nor the pink/black (hood ajar) wires out at the switch wiring at the core support. However, I have roughly 10 volts at both wires at the BCM connectors (X5 #15 & X4 #17). Should I have voltage at both simultaneously? I thought it was one or the other?
BTW I should add that the ground tests good out at the latch wiring.

Recommend you put your vehicle info in your signature (there's a section for that in your forum account).

I would also recommend getting a good bi-directional scanner on it to read the body code(s) that are calling for the error message. That will help narrow down the cause.

There is good info at www.charm.li - I'll put a couple of links below but once you get there, navigate to your vehicle using the links at the top of your browser window, and go to the similar pages for yours.

Connector pinout:

Hood Sensor/Switch (For Alarm): Diagrams — 2008 GMC Yukon 2WD V8-5.3L Service Manual | Operation CHARM

Detailed repair manual for the 2008 GMC Yukon 2WD V8-5.3L.

charm.li

Circuits Descriptions and Diagnostic path:

Hood Ajar Indicator/Message Malfunction — 2008 GMC Yukon 2WD V8-5.3L Service Manual | Operation CHARM

Detailed repair manual for the 2008 GMC Yukon 2WD V8-5.3L.

charm.li

Hope that helps.

 

[ccharlton]

yes voltage on both.

purple wire grounds when hood closed
pink/black grounds when hood open

tested wires at core support with latch switch disconnected?
If so, you must have a break or bad connection with wiring.

If you left the latch switch connected, then the switch could be grounding out the voltage.
But it should only ground one of them, so your new latch could be bad, *if* wiring checks out.

The latch was disconnected. I don’t understand how the system works apparently because where I’m from if you send power directly to ground that’s a short so I’m scratching my head

 

[ccharlton]

I see what it says but it would seem to me that if the BCM is pushing power to that switch and the switch is connecting it to ground it would be a dead short.

This is my thoughts exactly. It boggles my mind that the switch would send power straight to ground

 

[Fless]

A pulldown circuit like that is current-limited, and the internals in the BCM are made to recognize that as a switch, without overloading anything. It's designed that way; it's not a normal DC circuit that has a lot of capacity and loading. Many BCM circuits work like that.

EDIT: read up on both pull-up and pull-down circuits here: https://www.underhoodservice.com/tech-feature-dissecting-the-control-module-pcms-tcms-and-bcms/

 

[kbuskill]

This is my thoughts exactly. It boggles my mind that the switch would send power straight to ground

The BCM is looking for a ground signal on one wire or the other depending on latch position. The link @Fless posted should give you an idea as to how it works.

I would hook up a wire to the negative post of your battery or a known good ground and touch it to each of those wires on the latch one at a time and then check the message in the DIC to see what it says.

If that makes it function correctly then I am going to guess the ground wire leading into the switch is bad. If that doesn't make it function correctly then I would say you have a break in the wiring from the latch to the BCM.

 

[mikez71]

One of the connectors by the underhood fusebox & driver side fender liner might connect the hood latch to the BCM.
(P103, X103 on charm.li)

Since both wires show voltage at the BCM, but not at the latch connector with it unplugged..
Maybe you have two broken wires, or an unplugged connector under the hood?

 

[dkman610]

I'm getting a hood open error message when I roll up my windows. It's like I'm putting the car in park and it barks at me while rolling the windows up. In honesty, I did install a DDE Delete on the OBDII so I can't help but think that's what is causing it.

 

[Fless]

I'm getting a hood open error message when I roll up my windows. It's like I'm putting the car in park and it barks at me while rolling the windows up. In honesty, I did install a DDE Delete on the OBDII so I can't help but think that's what is causing it.

You may want to post your issue in the correct year section for responses, if that's what you're requesting.