99 Blazer LT 4.3
Where is the BCM, what does it look like, how should I go about this. My mechanic thinks this is a bad wire problem. He's told me this for a while but has no time to go through it for me.
The car has had intermittant start for a little over a year, now won't start at all, have replaced the fuel pump, Ignition Switch and Module. Had a Dealership run the codes, they told me it was the Fuel Pump and Ignition Module, all are new and working properly. The more I research, the more I think it has to do with the Passcode Security BS, probably bad wire or connections. can anyone help with my questions? thanks in advance, Doug

99 Blazer LT 4.3
Where is the BCM, what does it look like, how should I go about this. My mechanic thinks this is a bad wire problem. He's told me this for a while but has no time to go through it for me.
The car has had intermittant start for a little over a year, now won't start at all, have replaced the fuel pump, Ignition Switch and Module. Had a Dealership run the codes, they told me it was the Fuel Pump and Ignition Module, all are new and working properly. The more I research, the more I think it has to do with the Passcode Security BS, probably bad wire or connections. can anyone help with my questions? thanks in advance, Doug


Did the dealership get any codes?
If so post back codes.
Is fuel pressure up to 65 lbs on cold cranking?
Is the security light coming on key on and then going out or staying on?
Body computer usually sets codes if it has a problem.

Are you losing spark?
Are you losing injector pulse?
Will it start on carb cleaner?

Information and wiring and wiring pin out on body computer can be found in a factory repair manual or the All data on line sub.
http://www.alldata.com/products/diy/index.html

The Security Light seems to be coming on as normal. It flashes for 10 minutes after a no start then shuts off. I had fire earlier today but not enough to start it. I rechecked the plugs after i juiced up the battery and the light flashes in unison with the cranking for about 3 seconds then looks to develop a miss. I checked the Coil, it's good. I'll check the rest of the plugs tomorrow. keep in mind, i only have the cheap Spark tester that tests it at the plug. Might go ahead and replace the Plugs anyway...It will not start shooting ether in the intake either.

If light flashing antitheft has shut down injector pulse.

There should be codes point to problem.
Has anything been repace on switch or body module?

Try a relearn on system.
You will need a battery charger on it while doing it.
Key on 10 minutes untill light turns off turn key off and repeat 2 more times.
The turn key off and it should stat and light go out.

If light flashing antitheft has shut down injector pulse.

There should be codes point to problem.
Has anything been repace on switch or body module?

Try a relearn on system.
You will need a battery charger on it while doing it.
Key on 10 minutes untill light turns off turn key off and repeat 2 more times.
The turn key off and it should stat and light go out.

I have changed the ignition Switch, ignition Module, Fuel pump. The codes were for Fuel pump and Ignition Module, thats what the dealership told me but didn't cure the problem. I'll try the re-learn tomorrow morning.

I have changed the ignition Switch, ignition Module, Fuel pump. The codes were for Fuel pump and Ignition Module, thats what the dealership told me but didn't cure the problem. I'll try the re-learn tomorrow morning.


There is Not any codes for a bad fuel pump.

Go threw the relear and see what it does.
Let us know.

There is Not any codes for a bad fuel pump.

Go threw the relear and see what it does.
Let us know.

As my luck would have it, can't find the reciept from dealership. I'll call them tomorrow and get the codes from them. Thanks MT

There is Not any codes for a bad fuel pump.

Go threw the relear and see what it does.
Let us know.

OK, I called the dealership, they said I had low fuel pressure and 1 code #P1351. I replaced the ignition M odule and the Fuel pump, am in process of changing the Plugs right now. Tried the Re-Learn thing but the security light would go out shortly after turning the key to on?

Back to post no 2.
What brand of fuel pump did you put in it?
Got 65 lbs fuel pressure?
Got spark?
Got injector pulse?
Will it crank on carb cleaner?

Has code been cleared and rechecked for coming back?
Key on security light comes on and the goes out?

Back to post no 2.
What brand of fuel pump did you put in it?
Got 65 lbs fuel pressure?
Got spark?
Got injector pulse?
Will it crank on carb cleaner?

Has code been cleared and rechecked for coming back?
Key on security light comes on and the goes out?

Key on, light comes on then goes out. Will crank but not fire. Got spark but seems to have a miss. Bought a Delphi Pump(put an Airtek in last year, just replaced it), Gets 59 lbs then bleeds down to 56ish. My neighbor who is a Mechanic is going to help me check some electrical tomorrow.

Key on, light comes on then goes out. Will crank but not fire. Got spark but seems to have a miss. Bought a Delphi Pump(put an Airtek in last year, just replaced it), Gets 59 lbs then bleeds down to 56ish. My neighbor who is a Mechanic is going to help me check some electrical tomorrow.


Fuel pressure low.

Will it start on carb cleaner?

Does the engine start or not start?
What kind of miss?

DOES IT STILL HAVE CODES?



The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 75-85 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold and fuel pressure testing guide line.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak in system.
Post back fuel pressure readings.

Put a new Coil in it and it fired right up, will check again tonight and in the morning before I put everything back together. Thanks for all the help!

You welcome.
And thanks for posting back the fix.
Glad you got it going.