Code C1237, hard brake pedal, the brakes lock up?

Tiny
HULK78
  • MEMBER
  • 2012 HYUNDAI SONATA HYBRID
  • 2.4L
  • 4 CYL
  • AUTOMATIC
  • 180,071 MILES
C1237 The brake pedal is hard, and the brakes lock up and you hear a constant squeak under the pedal.
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Sunday, February 11th, 2024 AT 11:06 AM

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Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 107,645 POSTS
Hi,

The code is related to the active hydraulic brake booster pressure sensor. With your foot off the brake pedal, there should be 0 pressure being produced by the Active Hydraulic Brake (AHB) module. As you begin to apply the brakes, the sensor recognizes the change and adjusts the pressure to assist in braking. That is what makes the pedal easier to press.

Since the pedal is solid (hard to press), it appears no pressure is being produced or it is bleeding off at some point.

To test this, a live data scan tool is used to see if pressure is being produced. As mentioned, with your foot off the brake pedal, there should be 0 PSI. As you apply the brake, that should increase.

I attached the diagnostics below for you to see. Let me know if that is something you can perform or have done.

Take care,

Joe

See pics below.
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Sunday, February 11th, 2024 AT 4:46 PM

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