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P0704 OBD-II Trouble Code: Clutch Switch Input Circuit Malfunction

Check Engine Light

P0704 code definition

The powertrain control module (PCM) will detect and store the P0704 code if it does not detect a change in the clutch switch’s voltage signal when the clutch pedal is held down.

What the P0704 code means

When the driver holds the clutch pedal down while shifting, the voltage signal sent to the PCM from the clutch switch should go from high to low. If that signal does not change when the vehicle is in motion, the PCM will assume that there is a problem with the clutch or clutch switch and set the P0704 code, causing the Check Engine light to illuminate.

What causes the P0704 code?

The problems that can cause a P0704 to be set include:

  • A faulty or damaged clutch switch
  • A shorted or open clutch switch circuit
  • Damaged or corroded wiring or connectors in the clutch switch circuit
  • A poorly adjusted clutch switch

What are the symptoms of the P0704 code?

When the P0704 code is set, a number of symptoms can occur, in addition to the Check Engine light going on (which will always occur). The most common of these are:

  • The engine fails to start.
  • The engine will start without holding the clutch pedal down.

How does a mechanic diagnose the P0704 code?

Upon using an OBD-II scanner to determine that a P0704 code has been set, the mechanic will first inspect the wiring and connectors of the clutch switch to determine if any damage here may be causing the problem. If there is no damage to these, they will check to ensure that the Clutch switch is properly adjusted. If the switch does not open and close as the clutch pedal is held down and released, then the problem is likely with the switch and/or its adjustment.

If the switch has been adjusted correctly and the P0704 code is still detected, the switch may need to be replaced to solve the problem.

Common mistakes when diagnosing the P0704 code

Because this code can cause issues with starting the vehicle, it’s common to assume that the problem is actually located with the starter. Replacing or repairing the starter and/or components associated with it will not resolve the issue or clear the code.

How serious is the P0704 code?

Depending on the symptoms that occur related to the P0704 code, it may not seem very serious. However, with manual transmission vehicles, it is important that the clutch be engaged before starting the vehicle. If the vehicle can start without first engaging the clutch, it can cause other problems to arise.

On the other hand, the vehicle may not be able to start at all or may have a very hard start. This can be dangerous, especially if the vehicle is stalled in traffic and the driver needs to move out of the way.

What repairs can fix the P0704 code?

If a faulty or damaged clutch switch is causing the problem, then the best repair is to replace the switch. However, in many cases, the problem may simply be that the clutch switch is not adjusted properly or that there is damage or corrosion in the circuit. Repairing the circuit and ensuring that all connections are properly fitted could solve the problem without the need to replace the clutch switch.

Additional comments for consideration regarding the P0704 code

Whether or not the vehicle is displaying any other symptoms along with the Check Engine light being illuminated, it’s important to get this code resolved quickly. A faulty clutch switch can cause a number of problems, and if the Check Engine light is on, the vehicle will not pass an OBD-II emissions test, which is required for vehicle registration in most states.

Need help with a P0704 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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