This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.
P0700 Transmission Control System Malfunction
When there is a malfunction in the transmission control system, the check engine light will come on. Your car will also go into failsafe mode to prevent further damage to the engine. You can identify the specific problem by checking your vehicle with an OBD2 scanner. Code P0700 refers to this particular issue.
Before you can fix this problem, you need to figure out what caused it in the first place. In most cases, this kind of malfunction can occur for several reasons.
Faulty Transmission Control Module
The TCM monitors your transmission, including all of its sensors and actuators. These devices check the functionality of your transmission to ensure that it’s working correctly. If the TCM is faulty, it could be showing errors, even when nothing is wrong.
Transmission Valve Body Fault
Your transmission works by funneling fluid to different parts of the engine to help you shift gears and accelerate. The valve body is like the nerve center of the transmission, making sure that the right amount of fluid goes where it needs to. A problem with the valve could lead to malfunctions inside the transmission, causing the error code to appear.
Shift Solenoid Issues
The solenoid is the component that controls the flow of hydraulic fluid inside the transmission. It’s what helps you shift gears. The solenoid can break down, leading to problems with the fluid and your transmission as a whole.
Open or Short in the Wiring Harness
Modern cars rely on a variety of electrical systems to power the transmission and all of its sensors. A shorted wire or open connection can cause the whole thing to malfunction.
Because the transmission is integral to your car’s functionality, you want to be able to identify the problem quickly so that it doesn’t get worse and ruin the whole engine. Unfortunately, a check engine light doesn’t offer specifics, so you will want to pay attention to these symptoms to tell if it’s the transmission or something else.
Poor Gas Mileage
If you notice that your fuel tank is running out faster than usual, it could be because the transmission is working less efficiently, causing you to burn more gas to accelerate.
The transmission handles the shifting of your vehicle’s gears. If fluid isn’t flowing correctly through the valve body, you may notice the car jerking or taking longer to shift to a higher gear.
Engine Stalling or Dying
When the transmission fails, the engine will too. Not only can your vehicle stall because of this problem, but modern models will enter a failsafe mode, which could kill the engine to prevent further damage.
How to Diagnose Code P0700
Once you notice that your car is having transmission problems, you need to identify the specific cause. While you could try to fix or replace each component of your transmission, that will take too long, and it could be prohibitively expensive. Instead, follow these steps.
Step One: Use an OBD2 Scanner
Just because your car is stalling out or shifting irregularly doesn’t mean it’s the transmission control system. You’ll want to scan to find the P0700 code so that you know for sure. Here's a great one we use daily . Also, keep in mind that this code usually leads to other engine problems, so be prepared for additional work to get your car in pristine shape.
Step Two: Clear the Code and Test Drive the Car
Before you start tinkering around in the engine, you want to make sure that the code wasn’t a fluke. Clear all of the OBD2 codes and drive the vehicle for a little bit. If the light comes back on, see if the same codes return.
Step Three: Inspect the Transmission
You’re looking for any visible damage to the transmission, including the valve body and the solenoid. Also, double-check all wiring hookups to make sure that they are correctly connected.
Step Four: Utilize Live Scan Feature
If your visual inspection didn’t find anything, then you will need to use the live scan feature to see what’s going on inside the transmission. Fixing a transmission is complicated and must be done by a professional. Using this feature will help you identify if there is a mechanical or electrical (i.e., sensor failure) issue with it.
It might be tempting to start by live scanning your vehicle to see if there is something wrong with the transmission. However, you must go through each step one by one, as it’s easy to misdiagnose the problem.
Also, remember that transmission control system malfunctions can lead to other issues, so you need to take a more cohesive approach to diagnostics.
How Serious is a Transmission Control System Malfunction?
If the problem is simply a faulty sensor, then the car itself will run just fine. However, if there is something wrong with the transmission itself, you will likely have to replace it immediately.
The biggest danger is when your vehicle has trouble shifting gears. If the fluid is not flowing smoothly or reaching the right spots, it could lead to significant mechanical issues.
In the worst cases, the cost of repairs may be more expensive than replacing the car itself.
How Can I Fix the Code?
Once you identify the specific problem, your mechanic can go in and perform the proper repairs. These fixes can include:
Your vehicle’s transmission is one of it’s most crucial components. You must take care of it if you want to keep your car in tip-top shape.
Identifying and fixing this code immediately will save you a lot of trouble (and expenses) down the line.