Intermittent no start with passkey light on

Maintenance/Repairs
1

2007 Chevrolet Silverado Classic 1500 LT. 5.3 V-8 4-speed auto 4x4. 300k miles.

Last night, the truck failed to start for my son. I went to get him, jumped in the truck and it started right up. Today again it would not start, hours later it starts just fine. No codes. BTW, cranks OK, just does not start like it is out of gas. All lights work.

The only thing in the owners manual said was that if the light was on, the anti-theft system had been enabled.

A couple of years ago, the ignition key cylinder jammed and I replaced it with an aftermarket cylinder. Since then, the passkey anti-theft light would come on and stay on but it didn’t affect the truck in any way. It came on solid, not flashing. This is intermittent, rare at first but lately it has been coming on more often than not.

Last night it was on even after I started it and the truck made it home with no issues.

Today I poked around on the internet for some insight and wow, there is a lot of information that is inconsistent. Some say the key is supposed to have a resistor in it, some say a magnet, some say a chip and some say nothing in the key on 2007 classic and earlier.

There were a couple of videos about cutting a couple of wires and inserting a resistor between them but there were a lot of videos on a relearn procedure.

The relearn procedure was also not consistent between various videos, but I did stick my key in and turned it to on w/o starting the engine and let it sit for a few minutes. I did not wait the whole ten minutes and the security light did not go out, but when I started the engine, the passkey light went out and for now it seems to be working by the book. It comes on with the check engine light at start up but them goes right out.

I don’t trust it yet but I wonder if anyone here has some insight on the system. BTW one other thing, after the install of the new cylinder, there is no chime when the key is left in the ignition and the door is opened.

2

There is no resistor nor magnet in the key. I know that. As far as the rest, you are focused on the passkey system and nothing else. This could be a failing crankshaft position sensor. It would act the same way. And OBD2 scanner would help pinpoint that or something else as the problem.

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When I replaced the ignition cylinder, I went aftermarket so the ignition key is not original. When I got the truck, it only had one original key and that was worn out. I have been using duplicate keys and never had any issues until the cylinder jammed.

There are no codes. I checked with two different scanners, one of them reads GM enhanced codes, none present. No pending either.

4

https://www.justanswer.com/chevy/93rkm-2007-silverado-2500-theft-deterrent-light.html

Tester

5

Is that a “pay for site”?

6

Scanner, not reader. Get live data from the truck to make sure the cam and crank sensors are reading the rotation.

Check for fuel and spark and compression. Start with the basics and work your way along.

7

On a 2007? I am fairly certain that by 2007, these trucks would have a chip in the key, except maybe for the “work truck” trim level with hand-crank windows, etc.

Also, what about this?

Suppose for the sake of argument that the problem was something other than the security system, such as a failing fuel pump, ignition coil, crankshaft or camshaft position sensor, etc. How would that cause the security system warning light to come on?

This is a problem for two reasons. First of all, in a vehicle which is designed to have this feature, it would be very easy to accidentally lock your keys in the truck, because not audible warning will occur, and there’s nothing to stop you from locking the door and closing it behind you. At least on a car such as the Daewoo Lanos, which does not have an audible warning that the key is in the ignition, there is a mechanical interlock to prevent you from locking your keys in the car. The door lock lever on the driver’s door will not physically move to the locked position if the door is open. You must first close the door, and then lock it from inside with the lever, or from outside with the key.

Second, this tells me that the lock cylinder isn’t working properly, or isn’t aligned properly, which is what prevents the small reed switch from sensing that the key is inserted. If there is a chip which must be read and validated for the anti-theft system to function properly, it is not a stretch to suggest that this isn’t going to happen reliably.

8

My '04 truck has no resister in the key. My GM cars and trucks from the 90s did. That leads me to believe the 07 does not.

This is what leads me to believe the Passkey system is not at fault. The light comes on and the truck runs fine… but now it is intermittant all of a sudden? That seems like a red herring.

9

No experience w/that system, but my guess, the security system isn’t the cause. B/c it started ok after the ignition switch change-out. Presuming no recent work in that same area.

fyi, The way that works on my Corolla, there’s another small switch that’s part of the ignition switch ass’y. When a key is inserted, that small switch changes from open to closed, which in turn (in combo w/the door switch and harness wiring) sounds the audio alarm. It should be possible to test the continuity of that switch by disconnecting the ignition switch connector, but you’d need a wiring diagram to figure out which connector pins are involved. btw, I don’t think this is the cause of the no-start either.

If I had that problem my first step would be to check for visible spark during cranking.

10

The Passlock system uses a transponder key, no resistor. Passlock security system disables the fuel injectors when the proper key is not detected.

A flashing security light indicates an authorized key is not detected.
When the security light stays on, this indicates a system fault is detected.
A non-functioning key-in-ignition switch could cause a problem.

From the owners manual:

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image418Ă—525 68.7 KB

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11

Not my owners manual. Mine only says that if the light is on, the anti-theft deterrent system is enabled. Thats all it says.

I don’t have the original keys anymore and it now has an aftermarket lock cylinder. But as far as I know, it never had anything in the key. The 2007 classic is the same model as the 2004-2006. The change to the dew design was a mid year change. My 2002 Saturn had the Passkey 1 system and there was nothing in the key.

Problems with the passlock 1 and passlock 2 are well documented in both the Saturn forum I used to belong to and now on the Sierra/Silverado forum I joined. It all involves intermittent no start and the light being on. The most common solution seems to be is to cut two wires in the steering column and solder in a 2k ohm resistor and then do the relearn procedure.

I did a short relearn, that is I did it once instead of the three times in a row. So far the truck has started every time and the passlock light comes on with the ignition in start but goes off right after start and does not come back on.

However, i was looking for that elusive fuse that is supposed to be in one of the fuse boxes. Could not find it in the dash fusebox. When I opened the underhood fuse box, I discovered a lot of maple seeds stored in it and the tops of several fuses eaten right off. Most of the fuses looked good though, one not so good. No damage to the wiring though.

When did fuses start costing $5.49 each?

12

Pretty good clue to the cause of the symptom , rodents can do a lot of damage to a car’s wiring system in short order. I expect many shops would suggest to just replace the entire wiring harness in this situation, b/c a repair attempt is likely to incur a lot of expensive shop time.

It seems like for vehicle having security systems, one key design principle would be to always clearly inform the driver that the security system is preventing the car from starting. But maybe there’s an equally good reason to not do that.

13

Replaced the fuses, drove it a couple of times. So far the security light just comes on for about a second right after start up and goes right out. No issues yet.

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