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P0637 OBD-II Trouble Code: Power Steering Control Circuit High

Check Engine Light

P0637 code definition

The P0637 trouble code detects an issue with the power steering control circuit

What the P0637 code means

The P0637 code is a generic OBD-II trouble code that signals a problem with the power steering control circuit. The power steering control circuit sends data to the powertrain control module (PCM), and many of the other control modules, such as the transmission control module, traction control module, and fuel injection control module, and the cruise control module. When the PCM or one of these other control modules detects an issue with the powers steering control circuit, the P0637 trouble code will be triggered.

What causes the P0637 code?

The P0637 trouble code is usually the result of a malfunctioning power steering pressure or position switch. There are other possible causes though, including:

  • Damaged ground wire
  • Loose control module ground strap
  • In rare cases, a malfunctioning controller area network (CAN) bus
  • Damaged electrical components (such as wires and connectors) in the power steering system

What are the symptoms of the P0637 code?

The P0637 trouble code will usually be joined by the Check Engine Light illuminating on the vehicle’s dashboard. It is common for the power steering system to stop working, which means that steering may be difficult and heavy, and also erratic.

How does a mechanic diagnose the P0637 code?

The P0637 code will be diagnosed by using a standard OBD-II trouble code scanner. A reputable mechanic will use the scanner to assess the freeze frame data and gather information about the code. The mechanic will also look for any additional trouble codes that have been detected (codes should always be addressed in the order in which they appear). Then the mechanic will reset the trouble codes and restart the vehicle, to see if the P0637 and any accompanying codes return. If the code does not return, it was probably triggered incorrectly, or it represents an intermittent issue.

If the P0637 trouble code returns, the technician will perform a visual inspection of the system’s electrical components, as well as the ground wire and control module ground strap. If any of these parts is damaged or defective, they should be replaced immediately.

Next, the mechanic will inspect the power steering pressure or position switch, as this is the most likely culprit causing the P0637 code. If the issue still has not been found, the mechanic can use a CAN scanner to take a closer look at the control modules.

When any component is replaced, the trouble codes will need to be reset, and the vehicle once again restarted to see if the codes return. This helps the mechanic figure out as soon as the problem has been resolved.

Common mistakes when diagnosing the P0637 code

The most commonly made mistake in diagnosing the P0637 code comes from a failure to follow the standard OBD-II trouble code diagnosis protocol. The protocol should be followed at all times, step by step, to ensure that the inspection and repair is accurate and efficient.

It is common for other trouble codes to be diagnosed before the P0637 code, even when the P0637 code precedes the other codes in the freeze frame data. Since the accompanying codes may only have been triggered as a result of the P0637 code, addressing them first can lead to unnecessary repairs.

How serious is the P0637 code?

A vehicle with a detected P0637 code will still be drivable. However, the car will likely not have a functioning power steering system. The power steering system is a very important safety feature in any vehicle, and steering is difficult without it. Because of this, the P0637 code should be addressed immediately.

What repairs can fix the P0637 code?

Some of the potential repairs for the P0637 trouble code are:

Additional comments for consideration regarding the P0637 code

The P0637 code will commonly be accompanied by other drivability trouble codes, such as fuel injector codes, transmission codes, and engine misfire codes.

Need help with a P0637 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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