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Dan, Technician
Category: Chevy
Satisfied Customers: 23957
Experience:  Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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Chevrolet Express 1500: 2003 Chevy express 1500 van back turn

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2003 Chevy express 1500 van back turn signal lights use the same bulb for the break lights. When the turn signal comes on both work, but when break is applied only the passenger side comes on. Changed bulb! No power in the wire all the way back tracing it back past the fuses under the front seat. Would the problem be under the dash?

Welcome to JustAnswer, my name is XXXXX XXXXX I'm here to help get your problem solved. The light green wires that go to the backup lamp bulbs both get power from the body control module. The light green wires meet together at splice 404. So that either means the light green wire between drivers side bulb and splice 404 is damaged somewhere. Here is a picture of the splice and a wire diagram to help with testing. Let me know if you have questions or if there is anything else I can do to help. Thanks.



Customer: replied 3 years ago.

You mention the backup lamp bulbs, they work fine. I traced the passenger brake/blinker wire all the way to the dash and it comes on when blinker is turned on or when the brake is depressed, using a light bulb to check for power. Then when i trace back the driver side wire back past the fuse box under the seat to the dash, it comes on when blinker is activated and does not come on when brake is depressed like the passenger side.

Oops, sorry about that for some reason I thought you said backup lights. Give me a minute to give correct info for BRAKE lights. Thanks.

The turn signal flasher module gets signal from brake light switch and turn signal switch and then sends power to the bulbs as needed. Since the other side brake light is working we know the brake light switch and wiring related to switch is good. Since the turn signal works we know the wiring is good which means the flasher module is the only possible problem, here are replacement instructions. Let me know if you have questions or if there is anything else at all I can do to help. Thanks.


Customer: replied 3 years ago.
Correct, that is the part you need. Let me know how it goes or if you have any more questions, thanks.
Customer: replied 3 years ago.

Hey Dan, I removed the old flasher module just now, and replaced it with a new one. The blinkers work but now both brakes are out. So I put the old module back in and now both brakes are out instead of just the drivers side. Where do I start next?

It sounds like you have a blown fuse or bad brake light switch also. At the switch the red/white wire should have voltage at all times, if so jump red/white wire to white wire using a wire or paperclip, if brake lights come on replace brake light switch. If no voltage at red/white wire then check the 15 amp STOP LP fuse in location 7 of fuse box under the hood. Let me know if you have questions, thanks.
Customer: replied 3 years ago.

Dan, thanks so much! ! You saved me so much trouble and headaches. I ended up having to use a new flasher module and a new break light switch for both break lights to come on. You are a lifesaver!

Good to hear everything is up and running like it should be. Let me know if there is anything else I can do to help, thanks again and have a great night.
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