OT:04 silverado

[LisaK]

Im at my wits end with this pickup. Last fall the security light started intermittently coming on while driving. Shut off restart light out. No driveablilty issues
what so ever. 2 months ago i drove out of town about 8miles truck had no issues, no security light. It was 80 degrees out. Went to leave few hrs later it wouldnt
start. Fire and die. So the ex and his brother thought it was the fuel pump though we could clearly hear it cycle. Had it towed to the dealer next morning, wouldnt
start. Said ohms on the fuel pump read low (25ohms) Replaced fuel pump all was good..for a couple days..then returned to the no start and intermittient security light.
Had it towed again, next morning they said it fired right up for them. They kept my truck for 2 days claiming they tried to get it to stall (which wasnt the issue)
drove it around and what not. Well no they didnt it had the exact same mileage on it as when it was towed. So i took it back home. My next theory was the passlock
sensor so i shimmed it cause sometimes the plug being loose will cause issues. Went a week or more with no issues. Then back to the same thing. So I got the other key
out thinking it thought i was using the wrong key and shutting the vehicle down preventing start up. The original key was quite worn..Spare key worked for a week. 2
days ago the light came back on while driving home. No issues till yesterday. Took the kid to the park for an hr 85 and humid out no start...fire and die..tried 4-5
times. So i tried the remote starter...fired right up..What the heck is going on with this thing. its not throwing codes and the dealer cant figure it out. I dont want
to just start throwing parts at it being a single mom. Seems though the heat has something to do with it but could just be a concidence?

 

[Charles Krammin]

Lisa,
I had a similar problem on my 98 GMC "canyon" It would go along fine, for a long time and then all at once it wouldn't have "no Spark" at start up. The funny thing: If you waited 30 minutes the computer would reset its self and start normally again for awhile. They said I needed a new starter for $500. I felt they didn't know what they were talking about, so I installed a mechanics starter button under the hood directly from the battery to the solenoid.
I could activate the starter, but not start. next I engaged the mechanics switch and the key switch on the steering column (this engages the 12 volt start circuit to the coil). Still no ignition.
Conclusion: The "starter switch" on the steering column, was bad (like all the other lawsuits over bad key switches).
I took it in to a GMC dealer and talked long and hard to the mechanic, and finally convinced him. He went on his GMC site and it told him to replace the key switch on the starter column. They won't honor warranty, so I had them install a key switch for $200 from a parts dealer.
That was 2 years ago and the problem has been elminated.
I then tore apart the old key switch to see if I could diagnosis the problem . I was an "aviation radio repairman " in the service. It is very techinal, but here is my conclusion: The start cicuit, in the key has some copper points, that Ground to the diecast aluminum base. This is considered a ""dielecectric connection". This causes a electric surge to the computer, shutting it down. A "dielectric" is the same sensor in a gas hot water heater, or stove. " when heat is applied to 2 dissimiliar metals (copper and aluminum)it cause an electric current, that hold the safety valve open, to allow the burner come on, and if the pilot light goes out, the flame goes out.
GMC engineers know all about this but don't want more lawsuits then they have already. I don't think they have sent warning out to everybody, since, : "this is a start problem and not a safety item"

Charles Krammin

 

[Hobo,NC]

https://www.google.com/?ion=1&espv=2#q=2004 chevy silverado security light on no start

Said ohms on the fuel pump read low (25ohms)

Never heard of that'N... I could believe pressure was low even with the pump straight wired but I was not there.

security issues can be very intermittent

The most common repair is to replace the ignition lock cylinder and Passlock sensor and perform a relearn procedure.

Until you can do better read the link it should show how to reset it to get you home. The reset on new parts is the same song and dance... Some resets take fast some you get to jump through hoops till you get it to reset/relearn.

 

[Bob]

Security system is fouling up. It's easier to shut it off permanently than to fix it.

Find a "tuner" shop with "HP Tuners" or "EFILIVE" or similar software and have them edit "security"/passlok out of the BCM (body control module". $200, give or take, and NO parts needed.)

What is happening is that the powertrain 'puter allows engine to fire up for 3 to 5 seconds, then BCM says, "WHOA,NO go, somebody is trying to steal us" to the PCM and it shuts off fuel injection. (Or maybe tells the PCM not to listen to that demand from the BCM I don't remember exactly.)

The "mod" will shut off the BCM's ability to biatch to the PCM, demanding engine shutdown, ending the issue.

"JET" has some products to allow you to do this yourself on certain models. It might be worth calling them to see if they have a product that will work with your truck.

 

[Bob]

NOT to oversimplify, but the pickup uses a "Hall effect sensor" to detect a pattern of motion of the lock cylinder that is seen when the correct key is inserted vs. the motion caused by "picking" the lock.

NOT a single "dielecectric connection" in that whole infernal mechanism.

 

[grapeview8n]

Lisa, I work on these for a living. Sounds to me like your dealer doesn't have anybody worth their salt. Or certainly the info you give the service writer isn't getting passed on to the tech. Intermittant start/die and security light will almost every time be the passlock sensor. The fact that remote start works will back that up.The key on your truck is only needed for the mechanical cut to turn the cylinder. Anything else wrong would cause the start/die regardless of how you start the engine. The passlock sensor is the lock cylinder housing on the steering colomn. Unfortunately not an easy DIY project. But if you have the right tools and some patience you could manage it.
After replacement, a "theft learn" is needed. You start the engine, when it dies you wait for the security light to go off (aprox. 3 minutes), then repeat up to 3 times. (A battery charger is a good idea, since the key has to be "on" during this process). When the learn is complete, the truck will start and run with no security light.
Good luck, and feel free to email me if you have questions or get stuck in the process. Single moms need all the support they can get!

 

[cowdog]

years ago I had an 95 GMC. when I started to read this I thought this sounds just like myold GMC. intermittent problems at first. more annoying than anything. It finally quit on my wife when she was visiting the girls in Grt Falls area. Had GMC dealer from Grt Falls work on it.. Ignition switch changed out, never did it again.

 

[Charles Krammin]

I feel the "Dielectric", is between the tumbler (key start) "Copper points" and the Key body (diecast aluminum). Corrision could also be a problem, like pitted points in a distributor. I am not the familiar with the "hall lock sensor"

I do however have great confidence, that replacement of the hole key assembly, solved the problem, in similar problemss which GMC tech service advisory, advised the GMC tech. The replacement key body has now worked flawlesslee for 2 tears.
Charles Krammin

 

[Tiger Joe]

I second the faulty passlock sensor.

And FYI for anyone reading this, Bob efilive cannot read or modify a BCM. Only the tcm and ecm.

 

[Bob]

Yes, I basically covered that... stating I couldn't remember for sure which computer is dealt with... my son is the tuner guy, and it's probably been two years since we've "fixed one of these. Below is what I wrote, and we now agree it's the PCM that gets "modded".

ANYHOW, the point is that the problem can been permanently fixed for less that parts and labor to REPLACE parts that MAY or may not solve the problem for any length of time.

Here's what I wrote as a CYA:

"(Or maybe tells the PCM not to listen to that demand from the BCM I don't remember exactly.)"

 

[Bob]

I can think of two cases in point where a car and a truck had similar issues even requiring tows to the dealership, all sorts of parts were replaced, and still failed intermittently, a couple thou spent on each (parts and labor and towing).

The "edit" the 'puter trick "fixed" both.

If the vehicle is pretty new and a person figures they need anti-theft, I agree, start throwing parts at it.

On the other hand, if it's a dozen or more years old and/or if anti-theft isn't a big issue the "edit" is a cheap and sure fix.

YAMMV!

 

[LisaK]

Thanks for the responses..i'll have to come back and reread them in a few days...Kiddo had some serious complications from a surgery 9 days ago.

 

[LisaK]

I'm off to the dealer to talk to them about it. Im going to see if I can get them to replace the tumbler and passlock sensor.

 

[grapeview8n]

Great, the cylinder should be OK, but it's cheaper to handle it all at once. Good luck and let us know how it works out.