The C0547 code indicates that the control module has detected an open circuit in the voltage supply line to a vacuum sensor. This sensor typically monitors vacuum levels for systems like brake boosters or HVAC controls. An open circuit means the sensor is not receiving the required reference voltage, leading to inaccurate or missing vacuum data.
The most common cause is a physical break, chafing, or corrosion in the wiring between the control module and the sensor, often due to heat, vibration, or rodent damage.
The sensor itself may have an internal open circuit in its power supply pin, preventing it from receiving voltage even if the wiring is intact.
Poor contact at the sensor connector due to corrosion, bent pins, or a connector not fully seated can interrupt the voltage supply.
The supply wire may be shorted to ground or broken somewhere between the control module and the sensor, causing a loss of reference voltage.
Rarely, the module providing the 5V reference may have an internal fault. This should only be considered after all wiring and sensor checks are exhausted.
It depends on the affected system. If the vacuum sensor is for the brake booster, you may experience reduced braking assist, which is unsafe. If it's for HVAC or a secondary system, the vehicle may be drivable but should be repaired promptly to avoid further issues.
No. While a faulty control module is possible, it is very rare. The vast majority of C0547 cases are caused by wiring damage, connector issues, or a failed vacuum sensor. Replacing the PCM should only be considered after all other possibilities have been thoroughly tested and eliminated.
A common test is to measure the sensor's internal resistance between the power and ground pins. If the reading is infinite (open) or zero (short), the sensor is likely faulty. Also, if proper voltage is present at the connector but the sensor output is incorrect, the sensor may be bad.
No, a vacuum leak typically does not cause an open circuit code. This code specifically indicates an electrical problem in the sensor's power supply circuit, not a mechanical vacuum issue. However, a vacuum leak could cause other related codes.