Sierra start but no run

[steez53122]

Hi I'm Nick I have an 03 sierra SLT 5.3 extended cab. The truck will start and run for all of a second. If I disconnect the blue plug on bcm truck starts and runs but no lights blinkers and when break is depressed truck will die. Now if I plug the blue plug back in and unplug far left plug I forget color now but I want to say grey the truck will do the same thing. Ik the blue plug is for security, lights, horn, cluster, and windows. Do not know what other plug does. And when I hook up a scan tool it tells me It can't connect to pcm. There is power and ground at the obd2. The cluster in the truck ik for a fact has to be replaced but I'm unsure where to look for other issues on why the truck wont run. Key cylinder signal is fine starter is fine all fuses are fine. But something is killing the power to the fuel pump. Any help would be appreciated..

[Jsdirt]

I had the exact same problem in a '00 Jimmy - ended up being a blown fuse in the underhood fuse box for the factory security system. I can't remember what the security light was doing, but it wasn't right whatever it was. Maybe blinking whenever I turned the key, or something like that.

 

I replaced the fuse, it fired up and ran. Never had a problem with that system after that (but had problems with every other system, lol).

[steez53122]

I checked all fuses. Today I was able to fully plug in except for two wires that control the cluster. If I try connecting either of those the truck will die. And now when I go to turn my lights on the truck dies as well. I will check fuses again to see what is up. Thanks for the advice.

[Jsdirt]

10-4.

 

Could be a dead short that is pulling the 5 volt reference down. The fun part will be trying to track it down.

 

Keep us posted on what you find.

[00_NUTT]

Yea I'd be interested too in that resolution!!!

[steez53122]

once I have the cluster rebuild it should all go away hopefully. If not ik its the ecu/pcm and the bcm. But I'm hoping its not. I will keep yall posted when I figure it all out.

[00_NUTT]

Man if you have some decent mechanical skills and a little bit of electrical skills you can repair your cluster yourself. While my truck is having issues of its own I figured the gauges needed to work since the problems are really weird. So my truck is an 05 Sierra and I was tired of looking at the something. A caddi membrane, blue needles, white leds and all new stepper motors and bammm New looking working cluster!!!! There's plenty vids on YouTube if your not sure on how to do it.

[steez53122]

I could have done myself but I said **** it. And the cluster was the issue solved almost all problems. Still have a slight issue with the lights but I'm figuring its a ground. But ya I can completely plug bcm in and everything works blinkers brakes.

[steez53122]

well I now have a new issue. Truck runs and starts but at a stop like with light on break pedal pushed truck will choke to stall. On freeway blinker in accelerating truck will choke for a second then come back and do it again. Any ideas?

[Jsdirt]

First place I'd be looking on that one is the battery. Check the cables and connections. If you have those emergency terminals on there, throw them in the trash and grab some good ones.

 

These things here cause more problems than they solve, especially on modern computer-inundated stuff: http://www.maneywire.com/universal-emergency-top-post-battery-terminals-p-168.html#1

[steez53122]

what are top post terminal connectors that you recommend? I have had these on my truck for a wile now with no problems. And once truck is running should all the power be coming from the alternator anyways? Also yesterday I put it into reverse and when I tried hitting the gas to reverse the truck stalled.

[Jsdirt]

Get the whole cable assembly with the terminal molded right in. Those E-clamp terminals allow water, road salt and subsequent corrosion. Doesn't take much. I hate those things. Whenever someone brings me a vehicle with electrical or drivability issues that has those clamps, I tell them I'm going to replace them before I even start troubleshooting. Eliminates so many headaches, especially up here in the Northeast.

 

Yes, the alternator supplies current to the system, but the battery is a buffer - without it, nothing will work on a modern vehicle. In the old days you could yank the battery right out of the car while it was running, and it would stay running. That's how we used to check a suspect alternator. Try that today, and you'll probably cook several magic boxes ... or at the very least, the thing will stall.

 

Any grounds you see around the engine compartment and frame, it would be good to remove, sand, wire-brush, or wire-wheel the contact areas, and reinstall. Just one bad connection can cause all kinds of strange things to happen.

[steez53122]

_{ya these terminals are maybe three months old I replaced all power wire in the engine and most of the grounds but ill keep looking. Slow day in the shop. Also the lights threw the ground wire were getting power. So I cut all grounds and grounded direct and light are bright and they were working till yesterday. Then this morning everything was fine for some reason. Thanks for all the help btw ill start doing that see where it takes me.}

[SpartanAutoworx]

Check the PCM Ground on the frame drivers side by the frame horn. 1 10mm bolt two wires go into it. Clean it and cross fingers. When I have a weird issue like what you describe I always check that ground before I start thinking about a bad bcm or pcm. Clean it and report back.

[steez53122]

Thanks ill give that a shot tm at work if I get the time.