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Q: Brake ABS CEL on/off . ABS pulses once during braking, electrical system goes weak, wiper and lights weak.

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When the truck starts, CEL for ABS and Brake light fluctuate on/off. Driving and when I brake, the ABS pulses once , can feel it in my foot. Headlights go dim, wipers run like they don't have much juice. At times, I have turned engine off with key out but engine continues running, put key back in, turn it on, wait for ABS/Brake CEL to go off then I can stop the engine.

My car has 141000 miles.
My car has an automatic transmission.

A: I don’t know if all this started happening ...

I don’t know if all this started happening simultaneously or if these issues have been slowly accumulating, but here is how I would proceed: begin with a battery test and clean and make sure to tighten the cable connections. Replace the battery if needed before continuing.

Next, test the alternator output and be sure to check for A/C voltage ripple from the alternator. Belt must be good and at the correct tension. There have been faulty brake fluid level switches found. There have been issues with both the instrument cluster and ABS system on these trucks. They must communicate with each other, and can be tested with a scan tool to gather any existing diagnostic trouble codes (DTCs) to assist with diagnosis. Check for codes and module communication on the network.

If you want to have this done, a technician from YourMechanic can come and diagnose the warning lights and any of the other symptoms your car is exhibiting so that correct repairs can be made.

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