after removing foot off brake pedal, engine stops. re-applying brake, gong pings and check engine light come on.

 

Aehmmm - o.k. will need a bit more here:

Which Blazer
Year
Engine type

Then - to get you right on the symptom. You were happily riding your Blazer, then stopped, parked it and turned the key to "OFF".
But the engine refused to stop. When you did release the brake pedal it did stop running. Once you pushed the brake again, the CEL light came on.

What since? Have you been trying again? Did it run? And stop? Same symptoms?

About the "not stopping to run". Did it idle normally? Or was it something which is called "dieseling" (Rough coughing irregular idle)?

That may give us a bit more information to work on.

 

Sorry, 2001 , 4.3, 4L60 4wd. It runs with key off, and removed, as long as the brake is on, every time. It is not 'dieseling. before reinserting the key, brake on brings a Check engine soon light with 'gong'. Chuck

 

Do you have any aftermarket accessories that could be backfeeding from the brake light circuit through the ignition circuit? Maybe an electric trailer brake controller?

 

none.

 

There aren't too many places where the brake light circuit and the ignition circuit could cross. The only other one I can think of off the top of my head would be the ABS module, and I'm not sure without looking at a wiring diagram if that has a brake switch input.. Maybe unplug that and try it?

 

I'll do that and thank you! I do have a ABS light on all the time. My wheel sensors are bad. Chuck

 

Good luck. I'm just kind of taking a shot in the dark at it, so I may be way off, but hopefully it gets you on the right track. Maybe try pulling out the fuse for your brake lights and see if that has any effect.

 

This is one for the 2nd gen electric specialists here on the Forum.

If it continues to run "normally" even with the key off, it means it's not just the ignition but the whole ECU (ignition and injection) which still believes the key is in the "RUN" position.
Wiring diagrams needed!
I'd go from the ignition switch first and check which contacts do supply which accessories.

Then as a preliminary i'd go with TomA. Check for any fumbling with the electrical system. Repairs, burnt wires patched up connections.

 

Pulling the break light 20 amp fuse under the hood cures the engine running problem. Also pulling the TBC fuse cures the problem and starts the engine, but dies immediately. What in the h--- is the Truck Body Computer? Chuck

Finally I'm in pay dirt. Noticed the right turn signal has quit. With the left signal on or turn signals off, the problem persists. With the right turn switch on, engine shutS off fine, foot on brake pedal. Now, just gotta find out why! Chuck

another weird clue. With the hazard sw down (should be flashing, but does not, the above problem persists, with the hazard button off (up position), the above problem goes away, but the hazard lights flash! . Sorry I'm having so much trouble, but at almost 83, that's what life seem to be bringing to me bringing to me , Chuck

I pulled the turn signal flasher (behind the glove box) and the problem was still there, also found that I've lost cruise control. I was going to just order a new turn signal sw off ebay, but with cruise they are so expensive that I decided to wait and be sure. Chuck

one more clue and I'll quit looking and wait for some guidance/ advise. With the key off, if I keep tapping the brakes, the doors lock or locks chatter, especially if I hold the switch back like switching headlight beams. Sure seems like the turn signal, multifunction switch to me? Chuck

pulling the TCM (truck control module) fuse cured the key off, check engine soon light gonging when the brake pedal is touched, but with fuse pulled, engine starts, then dies. I could find no such module on the internet but there is such a thing as a Body Control Module. The BCM seems to interface with a lot of controls/ components and when bad causes strange symptoms. A copy and paste says 'If one or more of these symptoms are present at the same time, chances are it’s an issue with the BCM, and not the statistically less likely situation of multiple vehicle features failing simultaneously. If the problems occur intermittently, however, you might need to look into other causes, such as a bad battery or alternator – which won’t provide the level of voltage required for normal operation – or an issue with the fuses or relays in the electrical system. You can use a circuit tester to troubleshoot the electrical system yourself, but sensor issues are often best left to your local mecha.
Now I don't know whether to buy a new BCM or the Multifunction turn signal switch. Any advice will be greatly appreciated. Chuck

well, I have a good deal on a ebay BCM (Truck Control Module by owners manual). so I ordered it. If that isn't the problem, I'll go for the turn signal multifunction switch which is easily available and new. Just gotta hope for the best, Chuck