If you have a Ford model from the 1997-2003 Ford F150 Series or the 2006-2012 Ford Fusion make, you have likely come across the Code P1780. This could be a cause of concern if you have no vehicle expert to consult, especially when out on the road. So what exactly does it mean? Code P1780 is a transmission error code that indicates that the neutral safety switch has failed. Below, we tackle everything you need to know about Ford P1780.
What Does Ford P1780 Entail?
Some vehicles, such as Ford models, will often come with an automatic transmission control switch (TCS) located in the gear selector. If pressed, this TCS button prevents the transmission from going into overdrive. Consequently, the TCSL is activated when the TCS button is pushed. If the powertrain control module detects any TCS or TCSL circuit fault, code P1780 will be displayed.
What Are the Causes of Code P1780?
As per EngineCode, a Ford P1780 code could be a result of numerous issues, with the most common being:
- A faulty transmission control switch
- Wiring problems
- A faulty powertrain control module
- Failed TCIL
- The transmission control switch harness is shorted or open
Signs of a Ford P1780 Code
One of the signs of a Ford P1780 code will be a transmission that does not go into overdrive or one that has trouble coming out of overdrive. If you also have a faulty TCS indicator lamp and notice an illuminated check engine light, you will likely have a Code P1780. Unlike other vehicle errors, this code does not cause performance or driving problems.
How Do You Troubleshoot Code P1780
One way to troubleshoot the code P1780 will be by performing a visual inspection. Check if there are any loose wires in the transmission control switch or damaged buttons. You should look out for damaged components and even corroded pins. If there are any damages, repair these as needed or call for assistance from a qualified technician. If there is no physical damage, the next step will be conducting a key on engine running test (KOER) test.
For the key on the engine running test, turn the steering wheel back and forth, making sure it turns all the way while pumping the brake pedal. Turn the o/d button on and off during this process. Your TCS system is likely faulty if the Ford P1780 code is still on.
Inspect the Transmission Control Switch
Start by disconnecting the TCS from the connector. Next, set your digital multimeter (DMM) to ohms, and proceed to test the TCS. Press the TCS button and connect the DMM between the switch terminals. The meter readings should be less than 5 ohms, and the switch should also be depressed. According to experts at FIX TROUBLE , the meter should record an approximate 10k ohms when the switch is released. If the readings displayed are not within these parameters, then the control switch is faulty and will need to be replaced. If the switch indicates OL when the button is pushed, it is out of limits and has an open circuit that will also need to be replaced.
Inspect the Ground Side of the Circuit
The next diagnostic step will be checking the ground side of the circuit. Like the previous step, identify the TCSC and disconnect it. A test light will also come in handy here, allowing you to connect the battery’s positive and TCS terminals on the connector’s harness side. If the light does not turn on, then the ground side of the circuit will need to be repaired.
Professionals also make it a point to state, “Consult the technical service bulletins,” according to the manufacturer’s guide. This step will be crucial to your troubleshooting since Code P1780 only caters to specific vehicle models.
Check the Power Side of the Circuit
For this, you will need to access the TCSC, after which you will be required to disconnect it. Next, turn on the ignition and check for power to the TCS using a test light. Use a test light to connect the battery negative terminal and the TCS B+ terminal on the connector’s harness side. This should illuminate. If this does not work, it means that the power side of the circuit is faulty. Your manufacturer’s wiring guide will come in handy here, allowing you to proceed with the repairs as needed.
Inspect the TCIL Circuit
The TCIL relies on the same power source as the transmission control switch, meaning both are likely to have similar problems when faulty operations arise. To diagnose the lamp circuit, start by disconnecting the TCS connector and its corresponding connector at the powertrain control module (PCM). Next, turn the ignition off and set your digital multimeter to ohm. Connect the DMM between the B+ terminal located on the switch side of the connector to the TCIL terminal found on the connector end of the PCM connector. If it indicates (OL) or is out of limits, then the TCIL bulb is faulty. It could also mean an open circuit between the TCIL and PCM needs to be repaired.
Inspect the Control Module Operation
Checking if the powertrain control module is faulty will require you to first remove the TCS or the TCIL connector at the PCM. Next, turn the ignition off and set your meter to ohms. Connect the meter between the negative battery terminal and the PCM TCS terminal. The meter should have a numeric value after you push the TCS button. If the reading shows an OL, then the power control module is faulty since it does not supply ground as required.
This test should also be applied to the TCIL part of the circuit. Connect the meter leads between the ground and the PCM TCIL terminal. If it indicates an OL reading, the PCIM is also faulty and will need to be replaced.
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