1998 Silverado Passlock Issue ---- ugh

[HotWheelsBurban]

Or maybe it is PL.
Fuel pressure returned yesterday - lots of it. But no start on the key and wouldn't continue running when switched from LPG to gasoline.

When fuel pump goes bad - does it stay bad? Or can they be a bit intermittent?

They can be intermittent, it's an electrical component after all! If you take a rubber mallet and give the middle of the tank a couple good smacks, and it wants to work right, good chance it's the fuel pump. Or at least a loose connection in it or the adjacent harness.

 

[Pinger]

They can be intermittent, it's an electrical component after all! If you take a rubber mallet and give the middle of the tank a couple good smacks, and it wants to work right, good chance it's the fuel pump. Or at least a loose connection in it or the adjacent harness.

Or what I did yesterday - gave it two pretty hefty inlet manifold backfires (messing with LPG calibration) and the gasoline pressure at the Schrader was the best I've seen! Still won't start or continue running when running though. Not even the first couple of seconds a dodgy PL will. Testing my patience!

 

[brian c lindsey]

The ones from Rock Auto - straight forward replacement or is some sort coding required?

you have to have old one in your hand , as there is a part number for each module , last 3 digits on mine was 955 , but there are several and once you buy it , you cant exchange for another number

 

[s98gmc]

i have a 98 , and my passlock module went out year before last , it was hard to get to ,(under radio and behind cd player ) but i did , and bought a reman out of st louis , mo for less money that the tune would have cost, they have a lifetime warranty, rock auto also sells them

My situation is a bit unique because my truck was already modified before it was mine. I have a 98 inside of a 91 cab and passlock is installed, but was disabled in some way. It was unplugged at the ignition switch and the harness is zip tied out of the way inside the column. It also will run with regular hardware store key blanks. However, after fixing the cross body harness behind the dash a couple years ago I forgot to plug the passlock module back in and it wouldn't run. Plugged it in and it was fine again. A short while later I had it dyno tuned and he tuned out passlock at my request since it apparently still does something. I don't know if it'll run with it unplugged at this point and I hope 22+ year old electronics don't cause future problems. I have enough of that already.

 

[Supercharged111]

Once you turn it off in the PCM you can Huck the passlock module. The PCM no longer seeks a signal from it.

 

[Pinger]

Any real vehicle thieves can work around it quickly,.

How do they do that?

They can be intermittent, it's an electrical component after all! If you take a rubber mallet and give the middle of the tank a couple good smacks, and it wants to work right, good chance it's the fuel pump. Or at least a loose connection in it or the adjacent harness.

Today, no fuel pressure.
Thing is though, I was looking through some invoices that came with the truck and there's one for a fuel tank module (£127, circa $150 - is that a pump?), Locking Ring, and filter dated June 2018 and another for a fuel tank strap one month later. And another fuel filter in March 2019.
If that's a pump and it's been changed that recently - what would make it so intermittent in operation? The wiring to it running rearwards or something in the PCM?

This looks less like PL as I'm not even getting the usual 2 seconds of start up.
I need to try and 'force' the pump via the relay connection and if I can get it to work consistently by-pass the PCM with either a manual switch on the dash or by taking a signal from the LPG system that instructs the gasoline injectors to stop working when switched to LPG. That way, surely the only thing that can stop it running is if PL gets to the injectors first.

Going slightly leftfield... the bulletin re remote start only mentions 'disabling' the injectors. Doesn't explicitly state whether by depriving them of electrical signal or fuel.
A two second delay while the PL module decides it's a theft attempt and denies injectors of their opening signal is a bit tardy for an electronic system that should be able to react in millie seconds. On turn of the key before cranking - the prime from the pump would surely be enough for it to run for two seconds even if PL kicked in the moment the key was turned to crank. And, the one other safety system I'm aware of (in the event of roll over) stops the pump.

 

[df2x4]

How do they do that?

The resistor bypass method is what came to mind. A PCM swap takes about five minutes as well, but that one would require knowing at least what engine was in the truck. Maybe "quickly" wasn't the best choice of words but if someone wants it bad enough there are ways.

 

[someotherguy]

A PCM swap takes about five minutes as well, but that one would require knowing at least what engine was in the truck. Maybe "quickly" wasn't the best choice of words but if someone wants it bad enough there are ways.

If that's the method of attack, they can get all they need from the VIN to come prepared. VIN can be had remotely by just running the plate. This of course assumes engine hasn't been swapped..

Richard

 

[Supercharged111]

How do they do that?



Today, no fuel pressure.
Thing is though, I was looking through some invoices that came with the truck and there's one for a fuel tank module (£127, circa $150 - is that a pump?), Locking Ring, and filter dated June 2018 and another for a fuel tank strap one month later. And another fuel filter in March 2019.
If that's a pump and it's been changed that recently - what would make it so intermittent in operation? The wiring to it running rearwards or something in the PCM?

This looks less like PL as I'm not even getting the usual 2 seconds of start up.
I need to try and 'force' the pump via the relay connection and if I can get it to work consistently by-pass the PCM with either a manual switch on the dash or by taking a signal from the LPG system that instructs the gasoline injectors to stop working when switched to LPG. That way, surely the only thing that can stop it running is if PL gets to the injectors first.

Going slightly leftfield... the bulletin re remote start only mentions 'disabling' the injectors. Doesn't explicitly state whether by depriving them of electrical signal or fuel.
A two second delay while the PL module decides it's a theft attempt and denies injectors of their opening signal is a bit tardy for an electronic system that should be able to react in millie seconds. On turn of the key before cranking - the prime from the pump would surely be enough for it to run for two seconds even if PL kicked in the moment the key was turned to crank. And, the one other safety system I'm aware of (in the event of roll over) stops the pump.

If they're calling it a module then it sounds like you have a late 97 or newer. Those have the pump in a bucket and of someone used a crap aftermarket piece it should be no surprise that it took a dump already. Pump should run for a couple seconds when you turn the key on. If you're not even getting that then time to break out the multimeter.

 

[Pinger]

If they're calling it a module then it sounds like you have a late 97 or newer. Those have the pump in a bucket and of someone used a crap aftermarket piece it should be no surprise that it took a dump already. Pump should run for a couple seconds when you turn the key on. If you're not even getting that then time to break out the multimeter.

Yep, a 1999.
Just can't get near it just now for other stuff going on. Just had a look at the Haynes manual wiring diagram and if the pump is functional, a manual on-the-dash switch could be a better option.
It's only needed - more wanted than needed - for start up and back-up as I'm running on LPG(propane). And all the time I am the pump runs needlessly. Being able to shut it on and off at whim would be good for it and me.