Powertrain, generic · Transmission

P0719 Brake Switch B Circuit Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

Brake switch B is the brake signal to the transmission module or a second brake switch channel, used to release the converter clutch, adapt shift strategy on grades and cancel cruise control. Low and high describe the signal voltage, and what that means depends on polarity: GM's converter clutch brake switch is closed at rest (12 V), while Saab's Trionic 8 sees 12 V when braking. Detection is always a plausibility check against driving: the brake reads applied during accelerations or never applied during decelerations. P0719 means the signal stays low. For GM that reads as brake applied: 2006 transmission modules flag it after eight accelerations without the brake releasing, without MIL. Saab's Trionic 8 flags the brake light signal not changing during four decelerations from 40 to 3 km/h and disables cruise control. The opposite is P0724.

Likely causes

Brake light switch faulty or misadjusted
Wire to the module open (GM) or shorted to ground (Saab T8)
Connector at the pedal box corroded
Brake light circuit fuse blown

Symptoms

  • Cruise control cannot be activated or switches off
  • Unusual shifting, converter clutch behaviour changed
  • No downshift on uphill grades (Subaru)
  • Brake lights stay off or on

Repair estimate

DifficultyEasyDIY possible
Parts and labour€20–150
Time0.3–1 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

brake switchbrake switch wiringtransmission control module

Related codes

P0703P0724P0571P0572P0573P0504

References: gsi.ext.gm.com, gsi.ext.gm.com, saabwisonline.com, saabwisonline.com.