How to Fix a P0700 Error: Transmission Control System Malfunction

OBD2 Scanners is reader-supported. When you buy through links on our site, we may earn an affiliate commission.

When your Check Engine Light illuminates on your car dashboard, the first thing you'll surely do is to scan for trouble codes. Are you seeing the code P0700? Don’t panic! We’re here to help.

This article will discuss the symptoms, causes, diagnosis, and possible fixes of the P0700 error code. We hope that this blog will be able to answer any of your questions regarding this issue. Read on!

What is Code P0700?

P0700 is a diagnostic trouble code indicating that the Transmission Control Module (TCM) has stored a fault. This code is also called a Transmission Control System Malfunction. 

The TCM is the computer responsible for monitoring all actions electronically and mechanically of an automatic transmission. When it detects a malfunction in the transmission control system, it will send a signal to the Engine Control Module (ECM) that will cause your Check Engine Light to illuminate and set the code P0700.

Symptoms of Code P0700

The TCM has a significant role in the correct operation of an automatic transmission. When it detects a problem, there are usually symptoms that the driver can feel. Some common symptoms of code P0700 stored in the TCM are:

  • Hesitation or lack of power upon acceleration
  • Slipping gears
  • Poor gas mileage
  • Transmission shifting problems
  • Engine stalling

Causes of Code P0700

When the TCM malfunctions, several causes can be the root of the problem. The most common causes are:

  • Malfunctioning speed sensors
  • Dirty transmission fluid
  • Low transmission fluid level
  • Problem with shift solenoid
  • Damaged transmission valve body
  • Open or short wiring
  • Faulty transmission control module

How to Diagnose Error Code P0700?

When diagnosing the P0700 code, you must be more careful because this code is associated with other transmission codes. In most cases, addressing the other codes would solve the issue without fixing the P0700 itself. So, don’t skip any of the steps below when diagnosing this error code. Let's get started!

Check for Other Trouble Codes

As mentioned above, checking for other codes is crucial. It might save you time in diagnosing as it could be that another code is causing the P0700. To perform it:

  1. Get your OBD scanner and plug it into your car's OBD-II port.
  2. Turn on the ignition, but dont start the engine.
  3. Select "read codes" from your scanner menu and hit enter
  4. The scanner will now read all of the trouble codes stored in your car. Look for any code and address it            before moving to the next steps.

The diagnosis will stop here in most cases as another code often causes the P0700 code to be triggered. If that's the case for you, your lucky! However, if fixing the associated codes won't fix the issue, you may have to move on to the next step.

Perform Visual Inspection

If you have noticed, performing a visual inspection is always present in our diagnosing process because, most of the time, it is the easiest and most effective way to narrow down what could be wrong with your car.

In this case, you will want to focus on inspecting all of the electrical wirings in your transmission for any fraying, kinks, or other signs of damage. If any damage has been found, you need to replace those wires. Did it fix the issue? If not, you may have to move on to the next step.

Check Transmission Fluid Levels and Condition

Transmission fluid is what allows your transmission to shift gears smoothly. If there isn't enough transmission fluid or it has become dirty, it can cause problems, including the P0700 error code.

To check your transmission fluid levels, simply remove the dipstick from the transmission fluid reservoir and check the fluid level. If it is low, add more transmission fluid until it reaches the "Full" line on the dipstick.

If the transmission fluid looks dirty, you need to flush the old fluid out and replace it with a new transmission fluid. To do this:

  1. Jack up the car and remove the transmission fluid pan
  2. Clean out the old fluid and debris from the pan
  3. Add new transmission fluid to the pan
  4. Put the transmission fluid pan back on and tighten the bolts
  5. Lower the car back down

Once you've added more transmission fluid or flushed out the old fluid, you need to reset the transmission. Please be advised that not all the methods of resetting the TCM are the same. They may vary from Integrated Power Module (IPM) to Totally Integrated Power Module (TIPM).

The IPM controls your transmission, and the TIPM does everything that the IPM does, plus controlling your lights, wipers, etc.

The easiest way to reset your transmission, especially if you don't know which module you have, is to:

  1. Disconnect your battery for 30 seconds to one minute simply. 
  2. Once you've done that, reconnect the battery and start the car. 
  3. Drive it around for a bit so the new fluid can circulate throughout the entire system. 
  4. See if the problem has gone away, but if not, you may need to replace your car's transmission.

We recommend bringing your car to a mechanic for this. But if you think you can do it yourself, we have a guide to replacing a transmission.

How to fix Code P0700?

In some cases, doing all the repairs and steps above cannot fix the issue, and the car will require a new transmission. If this is your case, dont worry, as we will try our best to help you! But before you start, you should assess yourself first and see if you have what it takes to do this job. If so, follow the steps below.

Step-by-Step Guide to Replacing Transmission

  1. Disconnect the negative battery cable.
  2. Raise and safely support the vehicle with jack stands.
  3. Remove the transmission fluid pan and drain the fluid.
  4. Remove the old transmission's cross member bolts, driveshaft, and shifter linkage.
  5. Transfer all of these parts to the new transmission (except for the torque converter, which stays with the        engine).
  6. Install the new transmission and torque converter into the vehicle.
  7. Reconnect all of the parts you disconnected earlier.
  8. Fill up the transmission with fresh fluid and bleed it if necessary.
  9. Start the engine and check for leaks. If everything looks good, take it for a test drive!

Common Mistakes When Diagnosing the Code P0700

As mentioned earlier, the P0700 code is often associated with other trouble codes that can clear the issue if they are addressed first. Some mechanics automatically assume they need to replace the transmission without checking for other problems first. And that is wrong! Aside from that, here are some of the common mistakes people make when diagnosing the P0700 code:

  • Not cleaning the connectors and checking for damage
  • Not properly bleeding the transmission fluid
  • Jumping to conclusions and replacing parts unnecessarily

These are the things that can cause people to misdiagnose or overlook the root cause of the problem. By keeping these in mind, you can save yourself time and money in the long run.

Code P0700 FAQs

1. Is the P0700 code serious?

Yes, it is considered severe because it can cause transmission shifting gear problems that lead to accidents.

2. Is it safe to drive with this trouble code?

Driving with the P0700 code is not safe because your transmission may slip into neutral or overdrive without warning. 

3. Can I use a typical scanner tool to diagnose this issue?

You can use any code reader or code scanner tool to diagnose the P0700 error code. However, it would be best to use an advanced scanner because it can provide more information about the error code.

4. How can I prevent the code P0700 from coming back?

There is no definite way to prevent the code P0700 from coming back. However, you can try some methods that may help:

  • Resetting your transmission module
  • Replacing the transmission fluid and filter
  • Checking the wiring harness for damage or wear

5. How much does a P0700 code repair cost?

The cost may vary depending on the severity of the problem. If you need to replace the transmission, it can be quite expensive. It will cost between $200 and $800 to have a mechanic diagnose the problem and fix it. However, it would not cost that much if the problem is just a loose wiring harness or a dirty filter.

Conclusion

Did this blog post help you fix your issue with the P0700 code? How did you find the diagnosing process? Daunting or easy? Fixing this problem can be difficult, but you can do it yourself with the right tools and information. If you have repaired the issue successfully, we will be happy to hear about your experience! Please share your thoughts below!

If you are still experiencing problems with P0700, please post a comment, and we will do our best to help you out. We also suggest visiting your local mechanic to get a professional opinion on what is causing the code. Thanks for reading!