Chevy Silverado owners may experience stalling or gear shift failure along with the P0700 trouble code. It indicates that their car’s faulty transmission control system may need replacement.
Understanding the meaning, symptoms, and causes is essential in diagnosing and fixing the code P0700 in your Chevy Silverado. Let us dive in!
What Does the P0700 Indicate?
A P0700 code indicates a transmission control system malfunction. When the code comes up during diagnosis, it signifies an issue with the transmission control module.
The Transmission Control Module (TCM), which is also known as the Gearbox Control Unit (GCU), is a kind of computer system like the Powertrain Control Module (PCM). It functions as a controlling unit for the transmission of automatic vehicles.
TCM is just like the PCM as it relies on data provided by the sensors in the vehicle. For instance, the Throttle Position Sensor (TPS) and the speed sensor.
Also, the speed sensors responsible for sending speed data to the TCM and PCM are the Vehicle Speed Sensor (VSS), Wheel Speed Sensor (WSS), and Turbine Speed Sensor (TSS).
The VSS supplies the TCM and PCM data on the vehicle’s speed. The TCM then uses the data to determine when to change gears at the appropriate time.
In addition, WSS sends signals about the vehicle’s actual speed, determined by the movement of the vehicle’s wheels. The TCM also uses this to determine the right time to change gears. It determines when to change the gear by correlating data from the VSS and WSS.
The combined information from all the sensors gives an accurate gear change timing.
But what happens when TCU is not responding? The code P0700 is thrown alongside a series of signs that would make driving your vehicle nearly impossible.
Symptoms
The code may come with a series of common symptoms that can point out the cause of the code. Some of those symptoms include the following.
01. Limp mode
Limp mode is a secure medium that allows your vehicle to immediately reduce power and speed when there is a fault with the engine or TCM.
Once the ECU detects a problem with the TCM, it automatically activates the limp mode feature. The feature ensures that no further damage is done to the engine or the transmission system. You should avoid driving the car at all costs when the limp mode is triggered.
02. Unexpected engine stall or shaft in gear
Another sign that your TCM is faulty is that the gear will shift unexpectedly. When this happens, your engine will most likely stall or power off.
Driving your vehicle in this state could be dangerous. Your vehicle can easily lose control and cause a serious accident, especially if this happens when driving on a highway.
03. Check engine/transmission light
One less intense but common symptom of the P0700 code is the check engine and transmission light. When you notice the transmission light, it shows something is going on with the TCU or related components like the sensors, wiring, or gearbox.
04. The car runs on two gears
One common problem people who have experienced TCM failure have is that their vehicle only runs in first and second gears. This is a serious issue, and your car will quickly become a real hazard if this happens when driving on a highway.
05. No gear shift
Another common issue with the code is that the gear will not shift. In some cases, the gear will stay in the park or neutral, making it difficult or impossible to drive the vehicle.
In this case, you must immediately take your vehicle to a professional mechanic. You might need a tow truck or have a mechanic drive to you.
06. Bad Fuel Consumption
The TCM is designed in such a way as to put your vehicle in the best possible gear to improve fuel economy. When the TCM is faulty, your MPG will drop significantly. However, this is one of the last worries when dealing with a faulty TCM.
Check out our guides on how to fix other Chevy trouble codes: C0561, P1101, P2227, P00B7, and 7e8 Engine Code.
Causes
There are many reasons for the P0700; however, the major reason is usually a faulty Transmission Control Module. The cost of replacing your transmission control module will range from $500 to $1,000, depending on your make and model.
The following are other common causes of the P0700 trouble code.
01. Faulty Wiring
One common cause of the P0700 code is a short circuit or broken wiring connection. A problem like this will stop the TCM from collecting signals from all connected sensors and the PCM. When this happens, the TCM will begin to malfunction.
Diagnosing a fault with your wiring harness can definitely become time-consuming, but it won’t cost a lot to fix.
02. Bad Transmission Control Module (TCM)
There are a lot of ways the TCM can get damaged. Some of them may include dirt, cracks, and more. When the TCM fails due to dirt, you must check if the damage is serious; if not, clean the TCM and install it back.
Sometimes, giving the TCM a good cleaning and ensuring that the connections are not corroded will spare you a big repair bill. However, if the damage is more serious, you must replace the TCM. While the labor is not that expensive, the part will make up most of the repair cost.
03. Low Transmission Fluid
Another cause of the P0700 code is low transmission fluid. Many people do not pay attention to their transmission fluid. It is the reason they constantly have a problem with their TCM.
The transmission fluid has to be kept clean and changed regularly; if it is not done properly, it could make the transmission overheat, leading to a damaged gearbox. Ensure you stick to the service schedule provided by the manufacturer.
04. Bad Sensors
If any of the sensors that work with the TCM goes bad, the vehicle will detect a malfunction and might throw a P0700 trouble code. Replacing a bad sensor won’t break the bank, but it will surely take some time to find out which one you need to replace.
How to diagnose
Many people mistake the TCM problem for a gearbox issue. The problem will surely persist if you wrongly diagnose the issue.
To diagnose this problem, you can examine the TCM of the vehicle for any major damages. When examining the TCM, do not forget to check the wiring harness of the TCM. It is possible to replace a good TCM due to a faulty harness, which might end up costing more than needed.
You can also use an OBD scan tool or other good scanning devices to scan your car for a P0700 and other related codes.
How to Fix
There are various ways to fix a P0700 code. The fix depends on the cause of the code. The following are some of the ways you can fix a P0700 code.
- Fix or replace the harness wiring
- Replace or top up the transmission fluid
- Replace the TCM
- Replace any faulty sensors
Considering the knowledge required to fix a P0700, I recommend having a professional deal with this issue. It might not be cheap, but attempting to fix the problem on yourself might result in further damage and higher repair bills.
Can You Drive with the P0700 Code?
While some DTC codes may allow you to continue driving the vehicle safely, you should stop driving the car immediately when you get a P0700 error code. The severity of this code is high, therefore, by keeping driving the vehicle, you may put yourself and others at risk.
I recommend having the car towed to your nearest repair shop or having a mobile mechanic come to you and do the repair. There is a reason why the vehicle will go into limp mode when getting this code. This is to prevent further damage to your car’s transmission system.
Final Thoughts
The transmission is an important part of any vehicle and should be taken seriously. The Code P0700 shows that there is something wrong with your car’s transmission control system, and once it is diagnosed, you must take steps to fix it.
The repair costs might range from $250 to $1,000, and even more in some rare cases where you need to replace your vehicle’s transmission.
Mark is a senior editor for Mechanic Ask, creating tech-focused articles about diagnostics, tools, and new auto servicing methods. He attends industry shows to stay current. With a mechanical engineering degree, Mark is able to translate complex technical details into explanations understandable for shop owners and technicians. His articles help shops improve processes, reduce costs, and boost productivity.
