P0703 Code On 6.4 Powerstroke: What It Means & How To Fix?

The introduction of the Onboard Diagnostic System(OBD) has increased the probability of identifying and correcting your vehicle’s problems. This system shows different types of Diagnostic Trouble Codes (DTC) that indicate different problems with your vehicle. 

The P0703 code on the 6.4 Powerstroke means that the engine’s torque converter brake switch circuit is troublesome and, as a result, the cruise control has failed. The P0703 DTC indicates that the powertrain control module(PCM) has found a problem in the torque converter or the brake switch B circuit. 

So, what should you do if you see the P0703 code? To help you out, in this article, we will discuss what this code means, its symptoms, and how to fix it.

What Does P0703 Code Mean On 6.4 Powerstroke? 

The P0703 code mainly indicates that there is a problem in the brake switch B circuit. The brake switch receives a signal from the pedal and transfers it to the PCM. 

Then the PCM controls the TCC lockup function. If any received signal from the brake switch does not meet the expected values, the PCM sets a P0703 code to inform you that there is trouble.

If we break down the P0703 code, we will get:

  • P-  Here P indicates powertrain, which means engines and gears. Codes that start with P indicate trouble in the engines or powertrain.
  • 0- 0 is a code for standard OBD-II 
  • 7- Certain numbers are used to identify which system is faulty. The number 7 indicates that there is a problem with the “transmission” system.
  • 03- The last two numbers are used for describing the specific fault. In this case, the problem is “Malfunction in a Brake Switch Circuit.” 

How Serious Is Code P0703 On 6.4 Powerstroke? 

The code P0703 is associated with the brake switch circuit problem. Faulty brake switches disable the TCC lockup function, causing the engine to stall while stopping the vehicle and other driving issues.

Also, the cruise control stops working when this code is shown. You won’t be able to maintain a constant speed if cruise control fails. So, driving will become difficult as you will need to control the speed using the accelerator all the time.

Again, the cruise control is fuel efficient. Without it, your 6.4 Powerstroke will perform less efficiently. You will even need to spend more fuel than before.

The brake switch also controls the brake lights. If the brake light fails, viewing in the dark will get tough. So the aftermath of code P0703 is very serious on 6.4 Powerstroke.

What Causes Code P0703 On 6.4 Powerstroke?  

There can be several reasons for getting the P0703 code. The most common reason is faulty brake switches. Other possible causes that can force your 6.4 Powerstroke to store this code are:

  • Poorly adjusted brake switch
  • Faulty brake switch
  • Open or short brake switch harness
  • Poor electrical connection on the brake switch circuit
  • Damaged brake switch connectors or cable
  • Blown fuse or fusible link
  • Failed brake light bulb and damaged socket
  • Faulty PCM

Other Symptoms Of Getting P0703 Code On 6.4 Powerstroke

In your Ford 6.4 Powerstroke, a fault in the brake switch deactivates the cruise control and torque converter clutch(TCC). Thus, the 6.4 Powerstroke engine starts to perform poorly. The brake light also fails to work. Other symptoms are:

  • The cruise control does not work
  • Illuminated Malfunction Indicator Lamp(MAL) or Check Engine Light( the code appears in the memory)
  • Poor performance on 6.4 Powerstroke
  • The Torque Converter Lockup function fails
  • The brake lights do not work
  • Reduced fuel economy
  • Engine stalling

How To Fix The P0703 Code On The 6.4 Powerstroke?

As the code P0703 is related to the brake switch B circuit, fixing the brake switch circuit will clear the code. Properly connecting the cables and connectors will also fix it. 

But first, you will have to find out exactly where the problem has occurred. Follow the steps below to diagnose and  fix code P0703 on your Ford 6.4 Powerstroke:

1. Inspecting Brake Switch Circuit

To start the diagnosis, first you will need to inspect the switch circuit. If you find any blown fuses, replace them. Check for any faulty wires and repair them.

Check all the cables and connectors. Replace defective cables and tightly connect them to the port.

2. Fixing Misadjusted Brake Switch

If all the wiring and components are okay, then the problem must be in the brake switch. To check if the brake switch is working or not, you will need a code reader or OBD-II scanner, and a Digital Volt/Ohm Multimeter (DVOM).

Now, connect the scanner or code reader to the connector and record all the codes. Then reset the code and take the vehicle for a test drive to see if the code comes back immediately or not.

If it comes back, there must be other faults that need to be checked. But if it doesn’t:

  • Connect the DVOM machine and check the voltage on both the input and output sides. Keep the pedal depressed when checking the output side voltage.
  • If there is a voltage on the input side but not on the output side, then the case is that the brake switch is misaligned.
  • Almost every brake switch has the option of readjusting. Adjust it properly. If the problem isn’t solved, replace the brake switch.
  • If there is voltage present on both the input and output sides, then check if the brake lamps are working or not.

3. Replacing Brake Switch

When the brake switch gets damaged, the cruise control and TCC lockup also fail. In the Ford 6.4 Powerstroke, the brake switch is located underneath the hood on the master cylinder. 

You will find the switch at the front end of the master cylinder that supplies power to the cruise control. If the switch is open, cruise control will not work.

Follow the manual to remove and replace this switch. According to the manual, you should remove the battery and tray to access the switch. However, you can access it more easily by opening the driver’s side wheel inner splash panel without removing the tire and wheel.

There are two switches. You will need to replace the one that is closest to the firewall. Only a few drops of brake fluid may leak while doing this work. You don’t need to bleed the brake. Replacing the switch should activate the cruise control and make the code P0703 vanish.

4. Fixing Brake Lamp

Check the brake lamp and general underhood wiring. Replace or repair faulty wires. Replace any blown system fuse. 

Now, look at the brake lamp bulb. If it is damaged, replace it. Also, examine the socket to ensure it is not damaged. If it gets damaged, replace it with a new one.

5. Fixing PCM

If all the components are working fine, the problem may be with the PCM. though it’s a very rare case. To fix PCM, you must consult an expert mechanic as it needs programming to fix PCM.

How Much Does It Cost To Fix The P0703 6.4 Powerstroke Code? 

There are some costs if you need to replace the brake switch. The ID no of the switch is SW-6349 and the part number is 3L3Z-9F924-AB. It will cost around $30-$40 from Ford and up to $70 from other dealers.

Most repair shops charge around $75 to $150 for diagnosing a 6.4 Powerstroke engine. The diagnosis includes solving common codes like P0703.

Can You Drive Your 6.4 Powerstroke With Code p0703?

It is discouraged to drive your 6.4 Powerstroke with a code P0703. This code means that your brake switch is faulty. As a result, the brake lamps may stay lit all the time or may not work at all. It will cause serious problems while driving.

Again, failure of TCC lockup will cause the engine to stall, causing driving issues. Failure of cruise control results in poor fuel efficiency of the engine. So, driving with a code P0703 can be seriously harmful to your 6.4 Powerstroke.

Conclusion

While diagnosing code P0703, you must be careful so that you don’t misdiagnose anything. Follow the service manual that comes with your 6.4 Powerstroke. It will help you do the removal and fixing of the switch properly.

There are also some additional codes that you may see. For example, P0572 and P0573. These codes mean that the voltage of the circuit has been set too high or too low while fixing. Adjust the voltage properly when fixing.

Also, before replacing the brake switch, try to adjust it first. If the fixing work is hard for you to perform, try getting the help of an expert mechanic.

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