get on the brakes hard the abs and brake light comes on

1994 FORD F-350
16,300 MILES • V8 • 2WD • MANUAL
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ROBERT39
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  • 1 POST
when get on the brakes hard the abs and brake light comes on,when i turn off ing.and turn it back on again the lighs go off,,,,When i hook up a trailer(not pluged in)the lights will come back on and if i try to stop the rear brakes will lock up,,when i un hook trailer the brakes will unlock,,,,note the trailer is not pluged in,,,and everytime i turn the ing.off and back on again the abs and brake light will go off
Oct 2, 2010 at 12:08 PM
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MERLIN2021
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  • 17,250 POSTS
Have you removed the drums and inspected the rear brakes yet? Locking up could be a problem with hardware(return springs) or an axle seal leak. Possibly a frozen wheel cylinder.
Oct 2, 2010 at 12:12 PM
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TECH1FORD
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  • 102 POSTS
The first with the abs light and brakes light that is cause by the sensor on the rear diff or the wiring going to it. the trailer if you plug in the trailer and the abs light comes on you have something wired wrong. the only way for that to happen is if the connector on your truck or trailer is corroded and crossing terminals over.
Oct 9, 2010 at 11:32 PM
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SQM
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This could be an issue with the ABS module. A malfunctioning module can lock up the brake.
Best course of action would be to retrieve the ABS codes. As that can help with, the diagnostics.

Here is a helpful video:

https://youtu.be/rTtAnsOlZU4

I have attached diagrams for your reference.

Please let me know if you have any questions.
Thank you.
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Oct 16, 2021 at 9:59 PM