Hood Latch

Leon Owner/Technician Arkansas Posted   Latest  
Unsolved
Electrical
2018 GMC Sierra 2500 HD Denali 6.6L (Y L5P) 6-spd (1000)
Hood Latch Warning

Good morning to all, Have this Sierra in the shop that driving down the road the hood ajar warning will come in the dash, come on and go off, come on and go off. Checking the voltage at the BCM (I did test at the latch and got the same results as at the BCM) with my lab scope the voltage goes to 12V with the hood open and 3V with the hood closed and latched properly. The voltage does not change when the light comes on and off. I jumped the two wires at the latch and the voltage goes to 0V at the BCM. We installed 2 OE latch assemblies with no improvement. No evidence of wiring damage of any kind anywhere. Any ideas on where to go next? Thanks in advance.

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Matthew Technician
Nova Scotia
Matthew
 

Any trouble codes available in the BCM? Looks like the there are three sub codes to a B3006 - Hood Ajar Circuit which may help in figuring this one out.

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Leon Owner/Technician
Arkansas
Leon
 

It does have a B3006 stored in the BCM but I had the key turned on with the latch disconnected so I felt like that was irrelevant.

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Ruben Owner/Technician
Ohio
Ruben
 

are you sure there is no latch pin wear itself causing the latch to not close all the way? I am only assuming that the latch closed should read 0 volts any service info on that? any other wiring in line to another sensor causing the voltage issue?

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Matthew Technician
Nova Scotia
Matthew
 

Service info states BCM sends battery power to hood latch switch. Open switch and voltage stays high, closed switch voltage goes low.

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Ruben Owner/Technician
Ohio
Ruben
   

What Jon says. Can you jump the switch drive and see if code stays away?

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Leon Owner/Technician
Arkansas
Leon
 

Yes, and the light stays off. And the code stays gone.

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Jon Owner/Technician
California
Jon
 

Can you jump the switch and drive it?

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Leon Owner/Technician
Arkansas
Leon
 

Yes, and the light stays off

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Tony Owner/Technician
Missouri
Tony
 

Where did you jump it exactly, right at the switch connector, or?

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Leon Owner/Technician
Arkansas
Leon
 

right at the switch. I disconnected the hood latch switch and jumped it right there, and the light goes off and stays off.. Seems to me fairly conclusive that it is a bad switch/latch, but I already put two of them in…. If I had a wiring issue or BCM issue or IPC issue, my light would not go off when I jump the switch, would it??

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Tony Owner/Technician
Missouri
Tony
   

That's why I asked, as a disgnostic step. It only helps to say you jumpered it if you say where. I was considering an intermittent wire fault or pin fit/fretting issue which either didn't show itself during the jumpered test drive or was masked by your jumper tool/technique. Also the flexing of the connector when plugged into the switch vs laying loose could be affecting the wiring, pin fit, or…

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Raymond Mobile Technician
Michigan
Raymond
 

hi leon, watch scan data in bcm and catch at time of problem, also is that latch assembly adjustable? just trying to brainstorm ideas, HTH

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Tony Owner/Technician
Missouri
Tony
 

I see no mention of monitoring serial data. It doesn't matter what voltage is on the line if the BCM is flaking out internally. See what the BCM sees, and if all data is normal when the warning comes on you have a BCM or IP issue. But if the latch PID does go open during the warning you probably have a wiring or pin fit issue.

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Agree
Mark Engineer
Colorado
Mark
 

Tony You said: “you probably have a wiring or pin fit issue.” Based on the diagnostic logic and tests run to this point, I'm agreeing with your earlier post. I think we have a terminal “tension” problem and/or terminal fretting. If our OP says: “I disconnected the hood latch switch and jumped it right there, and the light goes off and stays off” I think you're right, it's not in the BCM or…

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Tony Owner/Technician
Missouri
Tony
 

Right, and still to be determined, was it jumpered with male pins in the female terminals? Back probed? Or were wires pierced? Testing methodology is more important than anything.

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Leon Owner/Technician
Arkansas
Leon
 

jumpered with a paper clip stuck into the female side of the connector.. not sure how to make myself clearer, I'm a redneck mukanik, not a lawyer.:))

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Tony Owner/Technician
Missouri
Tony
 

I guess your reply is supposed to be self-deprecating, but DID you say you used a paper clip before? Has this new-to-me info since been edited out? IS a paper clip the same size as your terminals, speculating they are Micro 64? DOES that test and results leave pin fit out of the question?

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Funny
Michael Technician
Indiana
Michael
 

Tony, off subject. The used car shop next door, brings me electrical problems. The cars always have at least two issues. The original failure. Then, also, every connector involved in the problem circuits, have been been wallowed out. Many times I end up having to bend pins on modules, to prove the Connector failure. Leon, Here is THE place to buy a terminal kit, it's a…

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Guy Diagnostician
New York
Guy
   

Hey Leon, did you check TSB’s? I remeber having a 18/19 with a hood ajar message and it was a loose body ground by the master cylinder, G218 i think it was. HTH.

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Robert Technician
Michigan
Robert
 

Just curious if scanner PID would show something when Lawyer jumps the hood latch terminals with paper clipping the latch connector . Please forgive all I read was 2 new latches and a DTC .

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Richard Instructor
Florida
Richard
 

jumping the wires at the hood switch is not really a valid test since the voltage should never go to zero. Take a look at the wiring diagram, the voltage shouldn't ever go to zero. There are two resistors built into the hood latch that should give the bcm different voltage drops based on whether the hood is popped or completely open. Driving the truck with scan data or a scope connected to that…

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