P0642 Fault Code

Sensor Reference Voltage A Circuit Low

• What does that mean?
• Symptoms
• Causes
• Solutions

The P0642 fault code indicates an issue with the Sensor Reference Voltage A circuit, specifically that the voltage is lower than expected. This code can appear in various vehicle makes and models, and it often signals a problem in the circuit that provides reference voltage to the engine control unit (ECU) or other sensors.

• The reference voltage is crucial for many sensors to function correctly and relay accurate information to the ECU.
• When the voltage is low, it can lead to incorrect readings from the sensors, which may affect engine performance and emissions.
• It’s important to address this issue promptly to avoid further complications.

What are the symptoms of the P0642 code?

Vehicle symptoms associated with the P0642 code may include:

• Poor engine performance, such as rough idling or stalling.
• Increased fuel consumption due to improper sensor readings.
• Potential illumination of the Check Engine Light (CEL).
• In some cases, diagnostic issues may arise, affecting the sensor data displayed on a scan tool.

What causes the P0642 code?

Several factors can lead to a P0642 code:

• Damaged or corroded wiring in the sensor reference circuit.
• Faulty or short-circuited sensors drawing too much current.
• A malfunctioning ECU that fails to provide the correct reference voltage.
• Poor electrical connections at the sensor connectors or within the wiring harness.

How to fix P0642?

To resolve the P0642 fault code, consider the following steps:

• Inspect the wiring and connectors associated with the Sensor Reference Voltage A circuit for any visible damage or corrosion.
• Test the voltage at the sensor and check for continuity in the wiring.
• Replace or repair any faulty wiring or connectors found during the inspection.
• Check for and rectify any issues with the sensors themselves, such as replacing them if they are determined to be defective.
• If everything appears normal, consider testing the ECU for functionality, as it may also be the source of the problem.