Trailbazer or Blazer? Trailblazer is quite different then a Blazer with different engine (4.2 inline 6 or 5.3 V-8) and different "common problems." In any case, I agree with your assessment here and your approach on what to check. A month ago, having studied what Steve was doing, and it was a little complicated because he had already messed with so many parts (both inner fender wells in and out), then focused on fuel pressure, which I thought was pretty good pressure to begin with, then plenum off, fuel pressure regulator, now security light flashing). On mine, it was throwing a code P0336 (crankshaft position sensor), so I replace the sensor wit an ACDelo but it still wouldn't start. It turned out to be chafed wire near the pigtail connector by the crankshaft sensor, which I could see had already been replaced, because someone had replaced the original sensor with an aftermarket sensor made in China that had scratch marks on edge of it where it must have been hitting the timing rotor. A loose connector plug on a crankshaft position senor will result in an intermittent circuit, stalling, and a no-start condition. Because of the intermittent circuit, the engine will run one minute and not the next, or in my case run for 30 seconds then die then eventually it would not run at all. The ECM was not getting a consistent signal. A faulty sensor or the sensor connector will result in same stalling and no-start condition. I had already checked the fuel pressure, had a new Delphi pump, checked and cleaned the MAF, new air filter, checked the coil and ignition module, replaced the cap and rotor with ACDelco cap and rotor. I kind of figured that after all that it had to be a short in a wire somewhere between the crank sensor and ECM and that's exactly what it was.If I hadn't found the short then my next step would have been to replace the cam sensor on the distributor or get another VIN-flashed ECM from Ebay, or through a company called Flashmasters ECM for $129.

What I outlined above are what happened to my vehicle, a 1999 Blazer 4wd 4dr 140K, and I am not saying that this is what is wrong with this one. However, it occurred to me that no where in these posts does it say anything about what codes it is throwing or if you tested the system with an OBDII scanner. This should have been the first step. Is the engine light on? Now, with the security light flashing and staying on, this could be the result of so many failed attempts to start it. I'm sure you did this, but first make sure the battery is fully charged. In the last photo posted, I notice a lot of electrical tape in patched areas along the outer split wire loom tubing sleeve. What happened here? Were any wires broken then repaired? Just buy new outer protective split wire loom tubing. Anyways, the passlock relearn process if starting from scratch, like with a new BCM, can sometimes take hours. But what caused this now? Then says, "If I disconnect the coil wire and yeah, crank for a bit and she'll run a couple seconds longer before she dies" Not sure what disconnecting coil wire has to do with this. And it still will stay running with starter fluid? I'm just trying to make sure there are not nore multiple problems involved n this now from what has already been previously done..

 

Well, I head posted a long response, but for whatever reason it didn't take.

I basically summarized everything i'd wish it would have posted. First of all, thank you for the feedback.

I have some due outs.
1. I'll recheck the fuel pressures, but I think we're okay.

2. I'll recheck to make sure that she still keeps running with the starter fluid as I did replace the spider.

3. I'll recheck any engine codes. There were none previously. Did have a lean condition code one time bank one. Don't remember the code, but I believe, I thought it could have been the catalytic converter. I had cleared that and it never came back. I also had a p 0440 evaporative system code. Never did figure out what it was. But the car ran just fine.

4. Anyways I disconnected the coil wire. Just to see if she'd put more fuel in while cranking. It did it runs a second or two vice immediately dies.

Someine recommended ignition switch replacement. I suppose I could do that, but I want to make sure that's the problem.

History. I've had the car about 2 yeard. Replaced the fuel pump and a broken fuel line. And we were off at running 8 months. Break booster went out big leak. Took me a months to fix. Wait, I got all done, put it back together. I got the.Start immediately die.

Questions I have on the security?
First by light only blinks when the door is opened or the hatch is open. Close it it shuts off.

turn key on it comes on for a little bit Steady, then shuts off and then I try to start and.I leave the key after start in ignition to do security relearn then it'll just come back on steady and stay there. In all the releard processes I see, it's supposed to blink?

i've done it.It waited much longer than ten minutes, it still stays steady with the ignition on.

 

Okay short update. Reverified fuel pressure. Starts off it 59 -60. Then, when fuel pump shuts off drops to maybe 56. Bleeds, down a couple p s I more. And holds for ten minutes and more. I'll take that as a pass. I didn't redo the pressure test at the filter.

I also confirmed she will still run by continually, spraying starter fluid into the carb.

No engine codes at all.

I took off panels. Underdash and looked at wiring. It doesn't seem to be anything out of place.

What next. I know someone had recommended I replace the ignition switch. But I really want to know if that will do it, perhaps. I'm assuming security issue for sure. Especially since when I tried to do the relearn, the security light will come on, go off and then come back on. Solid, and never turn off during that initial ten minutes.

So do I do the Ignition switch, or do I buy a high-end? Scanner and reset the security system is that possible?

Steve

 

The fuel injectors are fed by the ECM1 fuse and circuit which also feeds the IPC and the turn signals. If it was the ignition switch per say then you would lose at least turn signals when the truck dies. Also, you would lose power on the pink fuel injector power wires. If what they mean is the passlock portion of the assembly (the hall effect sensor and resistor value) then yes, broadly speaking it can be the "ignition switch" but also the BCM or PCM or their respective wiring. If your going to have to swap out the ignition switch then your going to have to do the passlock relearn anyhow. Another option is the resistor hack close to the computer module and then a relearn. That defeats a security deterent but would rule out the hall effect sensor, resistor and wiring to the computer. If done carefully it can all be put back to the default set up.

George

 

Thank you for the fast response. I acknowledge, I could do the ignition switch, but i'm hesitant, because I want to understand a bit more, why the security light what is doing and how that is controlled.

It blinks when I open the door or hatch. It comes on when I turn the key on and then goes off for a second. It will come back on solid after a second, whether I turn the key or not to start it. If I try the pass lock relearn, of course, it just stays solid, it doesn't go off after ten minutes.

What controls that light operation.

I will say that I replaced the driver's side window motor. When I first got the car. And now, for whatever reason it, it doesn't work again. I think the b c m does control that operation, but all the other ones work.

I've never lost turn signals to my knowledge, but then again, you know, it only starts for a second. And then dies. But that doesn't seem to be impacted.The turn signal still work.

i did check each injector are electrical with noid light. Then that works when cranking.

Thought maybe I i might have interfered with something when I put in the a brake booster, but i didn't see any thing out of whack per se.

 

Thank you for the fast response. I acknowledge, I could do the ignition switch, but i'm hesitant, because I want to understand a bit more, why the security light what is doing and how that is controlled.

It blinks when I open the door or hatch. It comes on when I turn the key on and then goes off for a second. It will come back on solid after a second, whether I turn the key or not to start it. If I try the pass lock relearn, of course, it just stays solid, it doesn't go off after ten minutes.

What controls that light operation.

I will say that I replaced the driver's side window motor. When I first got the car. And now, for whatever reason it, it doesn't work again. I think the b c m does control that operation, but all the other ones work.

I've never lost turn signals to my knowledge, but then again, you know, it only starts for a second. And then dies. But that doesn't seem to be impacted.The turn signal still work.

i did check each injector are electrical with noid light. Then that works when cranking.

Thought maybe I i might have interfered with something when I put in the a brake booster, but i didn't see any thing out of whack per se.

 

Are you just concerned about the security light? Does it run okay now? I have had a few where the security light would come on once in a while - one was due to a low battery. The 99 Blazer I have now it stayed on all the time but runs fine - no other issues. So I did the security bypass at the ignition switch but the security light still came on every time I opened the doors, and the problem is I often like to sit somewhere and read in the vehicle with my door open. To prevent it from coming on I just disconnected all the door light switches. Runs fine though. Your fuel pressure sounds great! I just put a brand new Delphi unit in mine and only gets 58psi. I think they just don't make them like they used to and now all the OEM units are outsourced outside the U.S, (usually Mexico) and even though they are supposed to be made to OEM standards, perhaps the tolerances aren't as close. I've tried an AC Delco unit and it wasm't any better. I don't know.

 

I have never fully researched all the different behaviors of the security light in our trucks and I don’t have time to go through the manual right now so I did a ChatGPT search and here is what I came up with in case it’s helpful for . These may be out of order.:













George

 

I reordered these screen shots because they were a mess

George