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2000 Blazer Fuel pump and brake lights working together.

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2000 Blazer Fuel pump and brake lights working together.

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Old 11-04-2018, 04:37 PM
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Default 2000 Blazer Fuel pump and brake lights working together.

Hey guy. As the title suggests I'm having some issues with a Blazer. It's a 2000 LS 2dr. I'm pretty sure it's a short somewhere just wondering if anyone would be able to point me in the right direction. My buddy and I were out and about when we noticed the brake lights wouldnt shut off. It has an aftermarket remote starter(possible problem??)

Upon getting to my buddies garage we discovered anytime the fuel pump kicks in the brake lights do as well. And anytime you step on the brake pedal even without the key in the ignition the fuel pump turns on. Any help would be greatly appreciated. Thank you in advance.
 
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Old 11-07-2018, 04:40 AM
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I would start with physically inspecting the area where the aftermarket remote was installed to see what the wiring looks like. Pull the fuel pump relay and see if the brakes still makes the fuel pump turn on, that will isolate half the wiring.

George
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Old 11-07-2018, 11:33 AM
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Also, have any of the windows been leaking and/or has there been any trauma to the inside floor/carpet especially on the drivers side?

George
 
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Old 11-08-2018, 01:30 PM
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Inspected the area where the command start is and I dont see anywhere that wires would be rubbing or chafing together. Yes the fuel pump still kicks in even with the relay removed while stepping on the brake pedal. There hasn't been any damage that I know of. But this all started happening while driving in the snow and on very wet roads.
 
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Old 11-08-2018, 02:20 PM
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What this means is that there is a short, most likely in a cable run between the brake power and the fuel pump power after the fuel pump relay. Now we need to narrow down which circuit (brake left, brake right, cruise control, hazard, trailer L/R).

Do you use the built in trailing wire harness that terminates at the back by the spare tire?

Have there been any water leaks into the truck making the carpet wet from doors, windows, floorboard, etc?

Do the hazard lights work OK both on and off?

Does the cruise control work?

Does the multifunction switch work OK?

Pull the following fuses one at a time, try the brakes, then replace that one and move on to the next one:

TR CHMSL 10A
VEH CHMSL 10A
TRR TRN 10A
RT TRN 10 A
TRL TRN 10A
LT TRN 10A
HAZ LP 20A
STOP LP 20A

Report back.

George
 
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Old 11-08-2018, 06:08 PM
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The trailer wiring harness at the rear of the vehicle is not used at all.

there has been no water in the vehicle that I can notice. Other then a small spot in the rear hatch on the carpet closer to the driver side which I assume is from the rear washer line leaking.

hazards, cruise, multifunction switch all seem to be working correctly.

checked all fuses in order. The only one that makes a difference is the TR CHMSL. With that one pulled the brake lights and fuel pump work as they should. Other then the remote starter which tries to start the vehicle but only turns it over and wont actually start it.
 
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Old 11-08-2018, 06:24 PM
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Boy did you get lucky. Since you don't use the trailer harness just pull TR CHMSL because that unused wire is shorted to the fuel pump power wire heading towards the back of the truck. The question then is how bad is the short/corrosion and will other circuits be affected. Follow the trailer harness wires from the spare tire area as far as you can towards the front of the truck to investigate. I think that this wire harness passes under the drivers side carpet but since this happened in slushy weather and there is no water inside then this problem is probably under the truck. Short term, you should be good.

George
 

Last edited by GeorgeLG; 11-09-2018 at 03:16 AM.
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Old 11-09-2018, 02:13 PM
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Thank you very much for your help. The vehicle is atleast driveable now. When we get some warmer weather I will try and trace the wire towards the front of the vehicle more. So far I've just looked at the wiring underneath along the frame and haven't found anything yet.
 
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Old 11-09-2018, 02:54 PM
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If the remote start feature is part of an aftermarket alarm system, then drop the trim panels under the steering column and check the wiring in there. Normally alarm systems cut into the fuel pump signal to be able to disable the engine and of course the alarm cuts into the lights so that they flash when armed and when the alarm goes off.

Most alarm installers use these cheap blade terminals to cut into a wire...these will fail...not if, just when.

Good luck with it. I saw remove it, but having remote start in a cold climate would be nice to have.
 
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Old 11-09-2018, 03:03 PM
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Your welcome, glad I could help. If you have any further problems post back and we will get you straightened out.

So that I understand, removing the TR CHMSL fuse caused the remote start to stop working or you were making a side comment that in addition to these problems, the remote start function was not working AND the brake lights/fuel pump were possessed (which is what I assumed)?

George
 
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