OBD-II Trouble Codes

P0641 Code: Sensor Reference Voltage “A” Circuit/Open

Reading Time: 3 minutes

The powertrain control module or PCM is your vehicle’s primary computer. It uses multiple sensors to monitor the operation of various systems that are crucial to vehicle operation (fuel, engine, transmission, exhaust, etc). These sensors communicate with the PCM by exchanging voltage signals.

Onboard sensors are typically supplied with a 5-volt reference signal by the PCM. Once the sensors verify it against what they were designed to measure, they return the signal to the PCM. If the latter detects a problem in the reference circuit, it stores a code P0641. If you’ve retrieved this code from your vehicle, here is some basic information that you should know.

What Does the P0641 Code Mean?

Diagnostic trouble code (DTC) P0641 stands for “Sensor Reference Voltage “A” Circuit/Open.” It is logged whenever the PCM detects voltage that does not match manufacturer specifications on the 5-volt reference circuit.

While most sensors have external reference circuits that are independent of one another, some are connected inside the PCM.

It’s common for the P0641 code to be logged together with a more specific sensor code. In cases where this trouble code is stored on its own, it’s likely that it was triggered by mistake as a result of a PCM programming error.

The P0461 code may refer to a problem in a different sensor circuit, depending on your vehicle manufacturer’s repair information. In some vehicles, it may refer to the fuel pressure sensor circuit, while it may point to an issue in the power take off (PTO) reference circuit in others.

car fuel pressure sensor
In some vehicles, the P0641 code may refer to the fuel pressure sensor circuit, while it may point to an issue in the power take off (PTO) reference circuit in others.

Note: The definition of code P0641 may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Possible Causes of the P0641 Code?

The code P0641 can be triggered by various issues, including:

What are the Common Symptoms of the P0641 Code?

Keep an eye out for these warning signs if you are dealing with a P0641 code:

How to Diagnose the P0641 Code

Identifying the underlying cause of the P0641 code can be difficult, especially if you’re not confident with your automotive knowledge. In most cases, it would be best to bring your vehicle to an auto repair shop and seek the help of a professional for an accurate diagnosis.

Here is a video that can help give you a better idea of how this trouble code might be diagnosed:

How to Fix the P0641 Code

The P0641 code is a generic trouble code that may apply to various makes and models. While vehicles from different manufacturers may share common symptoms, that doesn’t mean that they also share repair processes. For example, the steps for diagnosis and repair for a P0641 Chevy code may differ from those required by a P0641 Hyundai code.

If you’re an advanced DIYer who’d like to fix this code on your own, it will be helpful to refer to your repair manual or get factory vehicle repair information from an online subscription service.

mechanic checking car engine
If you’re not confident in your repair skills, you may have a certified mechanic or technician troubleshoot and fix the P00641 code for you.
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