But when those computer systems fail, they can be difficult to diagnose. In many cases, drivers first find out they have a problem when a code scanner displays a trouble code. Today, we’re going to look at one of those codes: P0700.
Tools Needed For Diagnosis and Repair
Before we talk about repairs, make sure you have everything you need to fix the P0700 code. This includes:
- – A flashlight or shop light so you can see what you’re doing
- – A Philips screwdriver
- – A universal socket set
- – Electrical contact cleaner
- – A multimeter
- – An OBD2 code scanner
What is a P0700 Code?
The P0700 code indicates that there’s a malfunction with your vehicle’s Transmission Control Module (TCM). This computer monitors your transmission and works with the Powertrain Control Module (PCM) and Engine Control Module (ECM) to shift gears when necessary. It’s an integral part of any modern automatic transmission.
What Does Code P0700 Mean For My Car?
If your TCM isn’t working properly, you can experience a drop in gas mileage, as well as rough, erratic shifting. These are concerns for any driver, but the biggest risk isn’t to your wallet or comfort; it’s to your safety.
In some cases, a faulty TCM can suddenly stop the car from shifting at all. Needless to say, if your car gets stuck in fifth gear on the highway, your life may be in danger. This is why it’s essential to diagnose and repair your TCM immediately.
Common Causes of the P0700 Code
There are three main causes of a TCM failure, which result in a P0700 code.
- – Low or dirty transmission fluid. Your transmission needs clean, full fluid to run properly. Low or dirty fluid can cause your transmission to overheat and results in excess friction between moving parts.
- – Faulty wiring. A short circuit or a corroded or broken wire can prevent your TCM from communicating with other car computers, leading to errors.
- – A dirty or failed TCM. Usually, this requires replacing the TCM itself.
Common Symptoms Associated With a TCM failure
Besides a P0700 code, you may experience other problems that alert you to a possible TCM failure. These include:
- – Your check engine light is on
- – Rough or erratic shifting
- – The car only runs in two gears
- – Your fuel economy drops for no apparent reason
If you’re experiencing any of these issues, you should have your codes read as soon as possible.
What Does Diagnosing the P0700 Code Entail?
To diagnose any automotive problem, it’s usually best to look for problems in order of how cheap and easy they are to fix. The first is dirty or low transmission fluid. This can affect your transmission’s temperature and performance, leading to anomalies in the TCM.
To fix this, first, check your transmission fluid to make sure it’s full and clean. Clean transmission fluid should be bright red. If your fluid is dirty, flush your transmission, and fill it up with fresh fluid. If your fluid is low but still red, top it off. Keep an eye on the level, though; it’s possible that you have a small leak which caused your fluid level to drop.
If everything is normal with your transmission fluid, the next thing you want to check is the wiring for the TCM. Using a multimeter, test all connections between the TCM and the ECM and PCM. Also, check the ground wire to make sure it’s not shorted out. If you find any issues, replace the defective wiring.
At this point, if you’re still experiencing problems, you can attempt a repair on the TCM itself. This process is somewhat advanced and is only recommended for people who are experienced with automotive repair. To learn more, read our detailed TCM repair guide.
If you’ve attempted a repair and your TCM is still returning an error code, you need to replace your TCM.
Common Mistakes When Diagnosing the Issue
The most common mistake when diagnosing the symptoms of a P0700 code is misidentifying the problem as a mechanical issue with the transmission itself. As you probably know, transmission repairs are expensive, far more than replacing a single computer. So not only will this type of misdiagnosis fail to fix the problem, but you’ll also spend a large amount of money having unnecessary work done.
If you suspect that your TCM is causing your vehicle’s problems, have your codes read, and look for P0700 or other TCM-related codes. If it’s a TCM problem, you’ll be able to fix it quickly and easily. And if it’s not, you’ll have the peace of mind of knowing that your problem really was a mechanical one.
Another common mistake is failing to check the wiring harness thoroughly. This can result in the replacement of a perfectly good TCM, while leaving the underlying issue unaddressed.
Possible Solutions For Fixing the P0700 Code
- – Topping off or replacing the transmission fluid
- – Repairing or replacing the wiring harness
- – Replacing the TCM
How Can We Help?
If it turns out that you need to replace your TCM, contact us via our web form, or call us at 888-848-0144. Our technicians have decades of experience repairing automotive computers and can walk you through the process of getting the replacement you need.