The P1780 is a manufacturer-specific trouble code common in most Ford vehicles. When the code is triggered in your Ford, it could result from an issue with your Transmission Control Switch.
- What Does the P1780 Code Indicate on Your Ford?
- What Are the Common Causes of a P1780 DTC?
- What Are Some of the Possible Symptoms?
- What Is the Average Repair Cost?
- What Should You Do If You Get This Code?
- How Do You Fix a P1780 Error Code?
- Closing Thoughts
The main cause is usually associated with the TCS circuit or any other related components that could affect the functioning of the TCS.
Although this Ford DTC (Diagnostic Trouble Code) might not come with any significant symptoms, getting it fixed as soon as you notice it is important.
We’ve put together a useful guide on the P1780 code, its causes, symptoms, and how to fix the issue.
What Does the P1780 Code Indicate on Your Ford?
The P1780 is a manufacturer-specific code for the Transmission Control Switch Circuit Out of Self Test Range. It is related to a problem with the Transmission control switch (TCS), and you can only see this code in vehicles with automatic transmissions.
In addition, the TCS button is closer to the automatic shift gear; and when pressed, it will disable the gear from going into overdrive. The switch is often labeled as OD off. When the switch is pressed, the Transmission Control Switch Lamp (TCSL) also comes on, indicating that the TCS is active.
Whenever this code is triggered, the Engine Control Module (ECM) detects a problem with the TCS or TCSL circuit. The circuit functions as a pathway for electric current to pass and get to the desired electrical component.
Electrical components, including the TCS circuits, rely on these circuits for power supply. The damaged TCS will cause a shortage and trigger the code on the OBD II scan tool.
When you put your key in the ignition and turn it to the ON position, the vehicle carries out a Key On Engine Running (KOER) self-test on all electrical components, including the TCS. It results in the TCS being cycled, and if the ECM notices a fault, it will trigger the code.
Related Ford Troubleshooting Guide: What Does the Code P0012 Mean?
What Are the Common Causes of a P1780 DTC?
There are many factors that could cause the trouble code P1780. Most causes are related to wiring issues in the transmission area and the computer system fault. Below are some of the common causes of the P1780 trouble code:
Faulty Transmission Control Switch
A damaged transmission control switch is one of the most common causes of the P1780 trouble code. A damaged TCS could mean damage to the button that activates the TCS or a failure in the system. In this case, when the system performs a self-check on the TCS, and there is no response, then the PCM will throw the P1780 Error.
The transmission Control Switch harness is open or shorted
Another major cause of the problem with many electrical components is a shorted wiring harness. The wiring harness is made up of wires that aid the flowing of electrical current and creates a communication line between the various electronic parts.
Once the wiring is damaged, the TCS circuit cannot transfer electric current to the TCS, which ultimately means it will not function.
Also, if the communication line is damaged when the switch is processed, the command will not be related to the appropriate computer system; in return, the system will trigger the code, indicating faulty communication.
Loose electrical connection
Another cause of the code is a poor electrical connection between the circuit and the transmission. When the connection is affected, the circuit can not transfer the needed electrical current to the TCS. Once the PCM detects this, the code is thrown.
Powertrain control module problems
The PCM monitors and controls a large part of the engine and other parts of the vehicle, including the transmission. When the TCS button is pressed, a signal is sent to the PCM, ensuring that the gear does not shift.
When the button is pressed, and the PCM does not receive the proper signals, or if the PCM does receive the signals but there is no proper response, it throws the P1780 trouble code.
When the PCM is damaged, it cannot perform its functions properly. So every signal from all the various parts of the vehicle may not receive a proper response from the PCM, which will lead to these parts finding it hard to function, and various codes being thrown.
Related Ford Troubleshooting Guide: What Does the Code P1129 Mean?
What Are Some of the Possible Symptoms?
The P1780 code does not normally come with a lot of symptoms. It is why many people do not take this trouble code quite seriously. However, there are some symptoms that P1780 may show, including the following.
Check Engine light
The Check Engine light is the first sign you will notice when the code is thrown. During the self-check, the PCM can detect if something is wrong with the TCS function. When the PCM cannot respond properly, the engine light is triggered.
Transmission stuck on overdrive or will not shift to overdrive
Another symptom of this trouble code is when the transmission will either be stuck in overdrive or will not shift to overdrive. The TCS plays a major role in ensuring that the transmission does not shift to overdrive.
When the code comes up, it shows the TCS is not working properly anymore. Automatically, the switch will not function like it used to, meaning when you push the switch, it could malfunction, making the transmission stay on overdrive, or in some cases, your transmission will not shift to overdrive even when TCS is not active.
Failed TCS lamp
When the TCS button is pushed, the TCS lamp is activated, showing that it works fine. The P1780 code, when thrown, does not come with an active TCS lamp, which means the feature is not working as it should.
What Is the Average Repair Cost?
The average price to fix a P1780 should be between $200 to $400. However, the price of fixing this could depend on the cause of the code. If the cause is due to a circuit problem, then the price should be about the cost mentioned previously. If the problem is related to the PCM, it would cost you more and can go up to $1,000.
Related Ford Troubleshooting Guide: Why Does My Ford Fusion Say “Power Steering Assist Fault”?
What Should You Do If You Get This Code?
When the code comes up in your Ford, you must diagnose properly to determine where the problem originates. To do this perfectly, you will have to check all the related parts of the vehicle that work directly with the TCS.
1. Check the circuit related to the TCS
The circuit is the major cause of this code. To test the circuit, you will have to disconnect the TCS switch. After disconnecting the TCS switch, test them for power using a test light. Test the connection between the TCS B terminal and the battery’s negative terminal. If the light illuminates, the circuit works fine; if not, it has gone bad.
2. Check the transmission control switch by disconnecting it from the connector
Then proceed to use a Digital multimeter to test for the TCS. The DMM should read about 5 ohms when pressed and 10 ohms when released. If it does not, then the TCS is damaged.
3. Check the Transmission Control indicator lamp (TCIL) circuit
You should be testing it because it is powered by the same source that powers the TCS. You will still need Digital Multimedia (DMM) for the test. To do this, you will have to unplug the TCS and other connectors to the PCM. Switch ON the engine, turn it OFF, and then connect the DMM to the appropriate terminals. The DMM should give out a value, but if it keeps reading or reads out of limit, then the circuit is bad.
4. Check the PCM. You can check the PCM by disconnecting the TCS and TCIL connection
Get the DMM and test the connection between the TCS and the negative side of the battery terminal. You can also use an OBD scan tool to test for code related to the PCM.
If you need help figuring out where the problem is coming from after doing all these, you need to get your vehicle to a certified mechanic for proper diagnosis.
How Do You Fix a P1780 Error Code?
After having a proper diagnosis done on your vehicle and the problem has been figured out, you need to have the cause of the code fixed.
Below is how you can fix the P1780 code on your Ford.
1. Replace Transmission Control Switch
If the cause of the trouble code is a failed switch, you will have to get the switch changed as soon as possible.
2. Repair/Replace any shorted circuits
Check all the circuits that the TCS uses and repair/replace any of them if damaged. Remember the TCIL circuits; if this circuit is damaged, it could also affect the TCS.
3. Replace the PCM
The PCM is always the last thing to check when codes like this come because the PCM rarely gets faulty. However, if the PCM is faulty, then you need to get it replaced immediately. A failed PCM could affect other vehicle parts if not replaced on time.
Depending on the model, you can find the transmission control switch in various places in Ford vehicles. In some cases, it could be a part of the shift knob. It plays an important role in the transmission system operation. You must change the entire shift knob or plate when it gets damaged.
I hope this article helped you understand the possible cause and solve your P1780 trouble code. You can do most of the checks yourself, but if you are unsure, it is recommended to have a technician check your car.