1998 Silverado-needs reprogramming help

[steve3408]

Does anyone have ideas on how to reprogram the pcm on 1998 silverados without taking it in to the stealership? It sat for about 2 years,battery went dead,will start if you feed it gas thru the throttle body but wont stay running on its own.A shade tree mechanic told me it needed to be reprogrammed and only a stealership could do that.Any helpful ideas on how to repair it? Will one of the high performance programmers that plug into the diagnostic port fix the problem,a little more power would be okay,not worried about the gas mileage issue.Had a few bad experiences with stealerships so i really,really dont want to take it in to them.
Steve

[rhandwor]

Some parts stores will reprogram. It used to be $50.00 if you brought it in.

[alblogg]

The way I done them is to unhook the battery for about 30 minutes then start it up. Sometimes you have to teach it to idle again so you put it in REV put on the Ebrake and let it idle for 5 minutes you need to sit in the truck unless you really trust your Ebrakes turn it off and start it back and it is reset. But it sounds to me if your truck is not running you might need to check a few things first before like fuel filter,plugs,cap etc before reseting pcm.

[steve3408]

Originally Posted by alblogg

The way I done them is to unhook the battery for about 30 minutes then start it up. Sometimes you have to teach it to idle again so you put it in REV put on the Ebrake and let it idle for 5 minutes you need to sit in the truck unless you really trust your Ebrakes turn it off and start it back and it is reset. But it sounds to me if your truck is not running you might need to check a few things first before like fuel filter,plugs,cap etc before reseting pcm.

It was running just fine before being parked.I changed the fuel and fuel filter,fresh battery,it will start if you prime it and feed it thru the throttle body,the "service engine soon" light is on when its running.I dont have a scanner to read the codes,but wouldnt think there would be much wrong with it just from setting,except maybe the computer just "zeroed out" or something from a dead battery.Its only got 28K miles on it, so its not wore out. Should i buy a economical priced scanner and try to figure it out myself?
I was an auto mechanic for years back in the 60's, 70's and 80's but this is a whole new technology to deal with,and i just havent been experienced with any newer stuff like it.
Steve

[steve3408]

Which parts store can do that? do you mean like NAPA stores or ADVANCE parts or AUTOZONE.... O'REILLY'S....??
Steve

[fleettech]

I would bet your fuel pump isn't working. I have never heard of a pcm having to be reprogramed after sitting for a while. if anything after you get it running it will need to relearn its fuel trim. if it will run by dumping fuel down the TB its not the computer.

[maxwedge]

fleettech, agreed, no such thing here, the fuel pump or some other similar fuel control related issue.

[rhandwor]

While I don't think it needs programming Bumper To Bumper used to do it I'm unsure about others.

[ChevyWonTon]

If you let it sit for 2 years, then the fuel injectors are probably painted on the inside with varnish. I think you'll need to consider replacement of the fuel injectors, but I don't know if your truck haa a fuel injected throttle body with a couple of injectors in it or separate injectors at the intake port of each cylinder.

However, I'd almost lay money on the injectors being plugged!

[steve3408]

Originally Posted by ChevyWonTon

If you let it sit for 2 years, then the fuel injectors are probably painted on the inside with varnish. I think you'll need to consider replacement of the fuel injectors, but I don't know if your truck haa a fuel injected throttle body with a couple of injectors in it or separate injectors at the intake port of each cylinder.

However, I'd almost lay money on the injectors being plugged!

Its a 98 with Vortex , injectors under the intake(i think)not in the TB.I was told it probably wasnt getting a pulse signal from the computer to the injectors,so fuel wasnt getting to the engine.
Cant the injectors be cleaned out? Will the fuel pump go bad from just setting? its not a high mileage vehicle,only got 28K on it.
What about removing the schrader valve on the fuel line and adding some kind of solvent to clear up any gas varnish in there,?????

[fleettech]

first thing you need to do is a fuel pressure test. the vortex motors are real picky about fuel pressure. If I remember its around 65lbs if it drops as little as 3-5 lbs they won't run very good if at all.

[steve3408]

Originally Posted by fleettech

I would bet your fuel pump isn't working. I have never heard of a pcm having to be reprogramed after sitting for a while. if anything after you get it running it will need to relearn its fuel trim. if it will run by dumping fuel down the TB its not the computer.

I can hear the fuel pump come on when the key is switched on, and depressing the inline schrader valve it sprays out with a lot of pressure,enough pressure...i dont know..?
Isnt there a pulse signal from the computer that operates the injectors amount/time open....?
How do you make it relearn the fuel trim?
(btw...sure appreciate the info help,THANKS)

[Blue Bowtie]

The fuel trim "relearns" itself after the engine is running and a "drive cycle" is completed. It continues to adapt and learn whenever the engine is run, is at temperature, and certain conditions are satisfied.

I'd agre that it probably didn't "lose" programming just sitting with a dead or dying battery. It it were subjected to heavy electrical noise from welding or some electrostatic source, the programming may have been corrupted, but even that is unlikely. At most, it lost the "learned" fuel and spark trim tables and is starting over with programmed base tables.

As for fuel pressure, a reliable gauge is really a necessity. The CPFI system requires 61 PSIG, and will start and run at 61 and not a 59. If you can tell the difference by depressing the Schrader valve core, you're a better man than I am. I need a gauge. You may be able to borrow or "rent" one from some parts stores which have a tool loaner program.