🚦 P0719 Code – Brake Switch “B” Circuit Low

If your car’s check engine light comes on along with a “brake light malfunction” or your vehicle suddenly enters limp mode, the culprit might be the P0719 code. This diagnostic trouble code means the Brake Switch “B” Circuit is reading a voltage lower than expected — often due to a faulty brake pedal switch, corroded connector, or blown fuse.

In this guide, we’ll walk through how to fix P0719 Brake Switch Circuit Low step-by-step using the iCarsoft CR PRO S — the same diagnostic tool trusted by professionals.

🔍 What Does Code P0719 Mean?

The brake pedal switch communicates with both the Powertrain Control Module (PCM) and the Transmission Control Module (TCM). Its signal tells the system when you’re pressing or releasing the brake pedal — vital for shift control, cruise control disengagement, and brake light activation. When the PCM detects a low voltage (below 0.1V) on the brake switch “B” circuit for a certain duration, it triggers the P0719 code.

⚠️ Common Symptoms of P0719

• Brake lights not working or stuck on
• Transmission won’t shift out of Park
• Vehicle enters limp mode
• “Check Engine” and “Brake” lights on dashboard
• P0719 code after replacing brake switch but not clearing

🔧 Common Causes

• Faulty or misadjusted brake pedal switch
• Corroded switch connector or wiring harness
• Short to ground in brake signal circuit
• Blown brake light fuse or failed bulb circuit
• Faulty PCM/TCM (rare)

🧰 How to Diagnose and Fix P0719 with iCarsoft CR PRO S

The iCarsoft CR PRO S helps confirm live brake signal voltage and determine whether the circuit is open or shorted. Follow these steps to accurately diagnose “P0719 Brake Switch B Circuit Low”:

1. Connect your CR PRO S scanner to the OBD-II port and power the ignition ON.
2. Select the ABS/TCM module for live data monitoring.
3. Press and release the brake pedal — you should see “ON/OFF” transition in real time.
4. If the signal remains “OFF,” check voltage at the brake switch connector using a multimeter.
5. Confirm the switch receives 12V supply on one pin and sends voltage out when pressed.
6. Inspect wiring near the brake pedal assembly for chafing or loose plugs.
7. Replace the brake switch if voltage output remains low or intermittent.
8. Clear the code and perform a road test to ensure the light doesn’t return.

🧠 Real-World Example: P0719 on a Mercedes C-Class

A 2018 Mercedes C-Class triggered the P0719 Brake Switch B Circuit Low code and couldn’t shift out of Park. Using the iCarsoft CR PRO S, the live brake signal stayed “OFF” even when the pedal was pressed. Inspection revealed a cracked plastic brake switch bracket preventing proper contact. After replacing the switch and clearing the code, the transmission operated normally again.

💡 Pro Tips to Avoid P0719 in the Future

• Always use OEM brake switches — cheap aftermarket versions often fail early.
• Keep pedal area dry and clean; water corrosion causes low-voltage shorts.
• Perform a full system voltage check if your brake lights flicker when pressing the pedal.
• After replacement, reset learned transmission adaptations using the CR PRO S for smoother operation.

❓ FAQs about P0719 Brake Switch Circuit Low

• How to fix P0719 brake switch circuit low?
  Test the brake switch voltage input/output, clean the connector, and replace the switch if voltage remains low.
• Can a bad brake switch cause limp mode?
  Yes. The TCM depends on the brake signal to control gear engagement. If the circuit reads low, the system may lock into limp mode for safety.
• How do I test the brake switch with a multimeter?
  Measure continuity across the switch terminals — it should show 0Ω when pressed and OL (open) when released.
• P0719 Mercedes brake light not working — what to check?
  Start with fuses, then verify power at the brake switch. If voltage is present but lights don’t illuminate, replace the switch assembly.
• P0719 code after replacing brake switch — what next?
  Clear DTCs with CR PRO S and check live signal again. Some cars require adaptation reset to recognize the new switch state.

📘 Conclusion

The P0719 code might seem minor, but a faulty brake switch can disable cruise control, transmission shifting, and even brake lights — making it a safety risk. With the iCarsoft CR PRO S, you can quickly confirm voltage readings, replace faulty components, and clear the code for good. Whether you’re working on a Mercedes, Chevy, Ford, or Toyota, this tool gives you dealership-level control at home.