What Codes Will This Page Cover?
On this page, you’ll learn more about all of the following codes:
- P0791 Intermediate Shaft Speed Sensor A Circuit
- P0792 Intermediate Shaft Speed Sensor A Circuit Range/Performance
- P0793 Intermediate Shaft Speed Sensor A Circuit No Signal
- P0794 Intermediate Shaft Speed Sensor A Circuit Intermittent
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What Is the P0794 Code?
Symptoms
Causes
Seriousness
Can I Still Drive?
Diagnose
Difficulty of Inspecting
Get Additional Help
The P0791, P0792, P0793, and P0794 codes indicate “Intermediate Shaft Speed Sensor A Circuit,” with P0792 indicating “Range/Performance,” P0793 indicating “No Signal,” and P0794 indicating “Intermittent.” These codes all indicate that your powertrain control module (PCM) or engine control module (ECM) has identified a problem with the circuit connected to your intermediate shaft speed sensor “A.” This generic error code can turn up on all OBD-II-equipped vehicles with an automatic transmission.
More About the P0794 Code
In an automatic transmission, it’s important that your vehicle has access to information about the speed of a number of different components in your vehicle to determine the best gear to shift into. The intermediate shaft, also called the layshaft, allows your vehicle to distribute rotational force from the input drive to the output shaft, with the speed depending on which gear you’re in. The intermediate shaft speed sensor circuit sends information from this sensor, allowing your transmission control module (TCM) to determine and adjust hydraulic pressures, shift points, and other patterns. These diagnostic trouble codes all indicate there’s an issue with the transmission intermediate circuit.
What Are the Symptoms of a P0794 Code?
Your first symptom will usually be the check engine light turning on. In many cases, other associated engine codes may also be illuminating other warning lights. Poor drivability is very commonly associated with this series of fault codes, as well as erratic engine speed, changing RPM very quickly. Due to these drivability issues, you may even see problems like engine misfire, which can be very harmful to your engine.
What Are Some Causes of a P0794 Code?
Even though this is an input speed sensor code, the underlying problem isn’t necessarily that the vehicle speed sensors are actually malfunctioning. Here are a few of the other causes that you might be seeing:
- Defective or damaged intermediate shaft speed sensor
- Electrical fault between the speed sensor and modules
- General electrical connection issues, including connector pins, corroded connectors, ground signal issues, and more
- Issues with the input shaft speed sensor
- Issues with the shift solenoid
- Dirty or low automatic transmission fluid
- Internal ECM, TCM, or PCM issue
To determine the actual problem, you’ll need to check what’s going on in your specific vehicle using the proper diagnostic procedures.
How Serious Is the P0794 Code?
Any code that creates problems with transmission components should be considered pretty serious. Even though fixing this problem may be as easy as having to flush transmission fluid, ignoring the issue can result in signs of damage throughout the transmission, which can be expensive and difficult to fix. When you notice problems with your transmission, even just problems with sensor inputs, it’s a good idea to treat it seriously.
Can I Still Drive with a P0794 Code?
Most of the time, an issue with a gear speed sensor signal isn’t enough to make your vehicle unable to drive. However, just because you technically can drive the vehicle doesn’t mean it’s a good idea. This problem can completely throw off shift timing, potentially causing problems with all sorts of systems in your vehicle, stretching beyond the transmission control system and into related systems like traction control. Whether it’s a faulty sensor or dirty transmission fluid, wait for an expert to help you fix the problem before you keep driving.
How Easy Is It to Diagnose a P0794 Code?
The diagnostic process for these codes can be quite difficult. This is partially because of how many causes can be associated with the codes, especially if you have multiple codes showing up beyond just these. Diagnosing a shaft speed sensor problem can require some knowledge of the specific vehicle you own. Talking to a certified professional will make sure that you fix the problem without making any of the common mistakes that tend to come along with fixing these kinds of codes.
How Difficult Is It to Inspect a P0794 Code?
Inspection, as with diagnosis, can be complex. Some of these codes require multiple failure cycles to set, and you’ll likely need to go back into the freeze frame data to determine the core issue. Regardless of what the actual concern is, you’ll need to put quite a lot of thought into it to determine the overarching concern, potentially including looking at a repair manual, comparing with specific vehicle models and transmission models, and looking for safety recalls and technical service bulletins. This is one reason a professional expert can help quite a lot with these codes.
Need Additional Help with Your P0794 Code?
The P0791, P0792, P0793, and P0794 codes can be very difficult to solve. If you’re finding that it’s difficult for you to fix the P0791, P0792, P0793, and P0794 codes, it’s important that you get an expert to help you out.
First, you should find an auto repair shop in your area. A local auto repair shop will have all the knowledge and information necessary to help you both determine the core problem and then fix the issue, regardless of what that issue is.
It’s also a good idea to check out the OBD-II database at KBB.com, especially if you also have other error codes popping up. This database can give you more insight into your core issues and give you an idea of the fixes that could be necessary.
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