01 The Truth About Fuel Additives: Do They Work and Are They S… • 02 Why Jet Engines Burn Less Fuel at Higher Altitudes • 03 How to Convert an Automatic Transmission to Manual (Pros an… • 04 Electronic Parking Brake: Benefits, Common Issues, and Cruc… • 05 Stiff Pedal, Stalling Engine? 6 Potential Fixes for High RP… • 06 How to Track Electrical Problems in Your Car with Clear Beg… • 07 This Is How to Fix Dim Headlights With a Simple Trick • 08 Nissan Engines: A Guide to the Most Popular Models and Thei… • 09 12 Luxury Cars Owned by Footballers That Cost More Than a P… • 10 Types of Chain Drives: Uses, Design, Application, Pros, and… •

DTC codes / C05xx · Brakes, steering and suspension / C0547

C0547Vacuum Sensor Supply Voltage Circuit/Open

C0547 indicates that the vehicle's computer has detected an open circuit or abnormal voltage supply in the vacuum sensor circuit, which is used to monitor vacuum pressure for systems such as the brake booster or EVAP. The powertrain control module (PCM) or body control module (BCM) sets this code when the sensor's supply voltage falls outside the expected range, often due to a wiring fault or sensor failure.

SystemChassis
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaBrakes, steering and suspension

Symptoms you may notice

  • Illumination of the check engine light or ABS light, depending on the system affected
  • Often no symptoms besides the warning light, as the vehicle may continue to drive normally
  • Reduced brake assist or a hard brake pedal if the vacuum sensor is part of the brake booster system
  • Poor engine performance or idle quality if the vacuum reading affects fuel delivery
  • Erratic operation of vacuum-operated accessories such as cruise control or HVAC vents
  • In some cases, a stored code without any drivability issues

Common causes, most likely first

  1. Open or damaged wire in the vacuum sensor supply voltage circuit (e.g., broken wire, corroded connector)
  2. Faulty vacuum sensor (internal short or open)
  3. Poor electrical connection at the sensor or PCM/BCM connector
  4. Blown fuse or faulty relay supplying power to the sensor circuit
  5. Water intrusion or corrosion in the wiring harness or connector
  6. Failed PCM/BCM driver circuit for the sensor supply voltage

How to diagnose and fix it

  1. Verify the code with a scan tool and check for any related codes in other modules
  2. Inspect the vacuum sensor and its connector for physical damage, corrosion, or loose pins
  3. Check the supply voltage and ground at the sensor connector with a multimeter, comparing to manufacturer specifications
  4. Perform a continuity test on the supply voltage wire between the sensor and the PCM/BCM to check for opens
  5. Inspect the wiring harness for chafing, breaks, or heat damage, especially near hot or moving components
  6. If the circuit tests good, test the sensor with a known-good unit or follow the manufacturer's diagnostic flow chart
  7. Repair or replace faulty wiring, connectors, or the sensor as needed, then clear the code and verify the repair

Don't Overlook the Supply Circuit

  • A common mistake is to replace the vacuum sensor immediately, but the supply voltage circuit open is often caused by a broken wire or corroded connector rather than the sensor itself.
  • This code can be set by a weak battery or charging system issue that causes momentary low voltage, so always check battery health and connections first.
  • On some vehicles, the vacuum sensor supply is shared with other sensors, so an open in that circuit may also set codes for those sensors, leading to misdiagnosis.
  • The code may appear intermittently due to vibration or temperature changes, so a wiggle test of the harness while monitoring live data can reveal the fault.
  • Do not confuse this code with a vacuum leak code; C0547 is strictly an electrical circuit fault, not a pressure performance fault.

Can I keep driving with C0547?

If the brake pedal feels normal and there are no drivability issues, you can drive the vehicle to a repair shop, but avoid heavy braking or towing. If the brake pedal is hard or braking performance is reduced, stop driving and have the vehicle towed to prevent an accident.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage