Hello all,

99 Bravada with 172k miles. Replaced engine about 2 years ago and has approx 30k on it. Was in a mildish flood about 4 months after putting the new engine in so electrical gremlins are a possibility. Water was up just under the seat bottoms inside. It was sitting at an angle so the passenger side was a bit higher. Water didn't get into the intake though. It is possible some got over the ECM (PCM). Gutted the interior. Cleaned it all out. New carpet, seats etc. Changed all the fluids, drove it a hundred miles or so then changed them all again.

Anyway, that was almost two years ago. It was fine after I got it running again after the flood. I've been doing a lot of reading on here and other places about this issue and I'm about out of things to change. This is the problem - It will buck, battery light comes on and it dies. Sometimes it starts right back up and sometimes not. It will die sometimes just sitting at idle. It appears random or at least no pattern I have picked up yet.

I like to think I've taken an educated guess shotgun approach to fixing it. I put a new Delphi fuel pump in it about 4 years ago. It's reading 60 with key on. About 54 while running. I've replaced the ignition switch (not the cylinder yet though) and BCM with a non-flooded BCM. Took the battery and tray out. Cleaned the grounds and the fusable link wires underneath that. New air pump after the flood though I do still get an occasional P0410 and I'm not sure why. New TPS, MAF, EGR, IAC valve, MAP, crank sensor, camshaft sensor, ignition control module, coil, fuel pump relay, alternator. All AC Delco or Delphi. Replaced the original spider with the upgraded Delphi model. Cap and rotor are good brass contact models and about 4 months old. Plugs and wires last year. No blown fuses. ECM fuses don't have any burnt contacts or anything. Pulled and jiggled on all the wires and harnesses under the hood and can't get it to shut off. I don't get any codes when it happens.

Any ideas? I don't know how watertight the PCM is and if water got inside it. The connectors all looked good.

*edit* I just read the other recent post about a Jimmy doing the same thing. Going to make the fuel pressure adapter and check that and also hook up the light to the coil to watch it.

 

Welcome to the forum!

Does the SES light work? Provided the SES light works with the bulb check, goes off after the engine is running, and there are no DTC's in memory, this means the problem is not something that the PCM monitors, (key word here being "monitors"). This lets out a ton of possibilities as to what is not causing the problem. It is posssible that the PCM is losing power though First step is to figure out if it's losing electrical feed or ground to the PCM, ignition system, or the fuel delivery system when the problem ocurrs. None of these will set a DTC in memory if/when there's a problem with them, but each one can cause what you're describing.

The test light that you mentioned in your edit will be your friend in diagnosing your problem. Attaching it to strategic circuits should narrow down the problem even further.

 

Thanks for the reply. I've lurked on here for a couple years as a reader figuring out to fix stuff on the floodmobile.

Yes, the SES light does work on the bulb check. All the lights on the Christmas tree work. Also, FWIW I have the Autoenginuity scan tool so I can read codes in other modules. At the moment, I have no codes in any module. After I replaced the BCM this past weekend, I did have a P1631 and a B2600. After I did the security program I cleared them both and neither has come back.

 

Autoenginuity should be a huge help in seeing if the ignition, PCM, or fuel pump circuits are losing power, might not need to do the test light thing. On the menu, bring up live data streams, and look for a drop out on each circuit when the problem occurs.

 

Had some time today to mess with it. Not sure what all sensors to have Autoenginuity watching so I chose these. You can see at 1:15:44 the ignition voltage dropping out to 0 at 1:15:58. The security system shows all fine the entire time. What should I be looking for now? Obviously something is causing me to lose ignition voltage.

 

How many data streams can you log at one time? I'll pick out some for you

 

I have the enhanced gm package so quite a few.

 

That's odd, 99 Bravada shows it could have either a W or an X engine. Pretty sure all that was available in 99 was a W. But I've been wrong before. What is the 8th character in the VIN?

 

It is a W

 

Thanks.

There were zero faults in any of the VTD circuits, no sence wasting time there.
Does the check engine light work?
Are there any DTC's in any of the 3 memory files?
When this thing dies, does it quit like you turned the key off?
Or does it stumble and then die?
Do any of the dash warning lights come on simultaneously with the first sign of trouble?


Lets try these for starters:

CKP (crankshaft position sensor)
Canister purge solenoid
Canister vent solenoid
MAF (Mass Air Flow sensor)
CMP (camshaft position sensor)
Knock sensor voltage
Ignition 1 on
Ignition voltage
Ignition 1 low
Reference pulse occurred
B1S3 Oxygen sensor