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P0609 OBD-II Trouble Code: Control Module VSS Output "B" Malfunction

check engine light

P0609 code definition

The P0609 code means that there was a malfunction detected in a vehicle speed sensor output from the PCM or many supporting control modules, such as the TCM, the body control module, the instrument panel control module, the fuel injection control module, and several others.

What the P0609 code means

Many systems within a vehicle must monitor vehicle speed, and they use this information to calculate values related to their own function. These systems may be controlled by the PCM, powertrain control module, or they may be controlled by their own specific control module. If any of these modules detects that the data from a vehicle speed sensor is incorrect or inconsistent, the system will register a malfunction, and will store the code P0609 in the PCM.

What causes the P0609 code?

Most of the time, a faulty PCM is a very rare event. However, in the case of the P0609 code, a defective PCM driver could be the root cause. Other causes may include:

  • Poor connection in the electrical components of the PCM
  • Corroded, shorted, or open wiring, or faulty connectors, in the CAN bus harness
  • Loose control module ground strap
  • Broken control module ground wire
  • Defective CAN bus

What are the symptoms of the P0609 code?

If the P0609 code is detected by an OBD-II scanner, it is probable that the vehicle has had performance issues. Harsh shifting, stalling engine, decreased fuel economy, rough idling, and difficulty accelerating may all be experienced. The Check Engine Light will be illuminated after several drive cycles.

How does a mechanic diagnose the P0609 code?

After an OBD-II scanner detects the P0609 code, a technician should begin with a visual inspection of all the wiring, connectors, and other electrical components related to the CAN. Any damaged elements should be replaced, reconnected, or repaired as necessary. They should then clear the code and retest the system, to be sure that the Check Engine Light does not reappear. If the code is restored after this test, the mechanic can move on to further repairs.

Common mistakes when diagnosing the P0609 code

Often when communication codes, such as the P0609 code, are stored, it can cause a chain reaction that results in many other codes being stored in the PCM memory. If these codes are addressed out of order, starting with the most recently stored first, it can result in unnecessary repairs. Mechanics should use the freeze frame data in the PCM memory and begin diagnosing and repairing the oldest code first; they may find that clearing one code will cause many others to disappear.

How serious is the P0609 code?

If the P0609 code is detected, it is considered a moderately serious issue that should be addressed. While the vehicle should still be operational, and there may be no serious ramifications of putting off the repair, it can still have an effect on the vehicle’s operation, making it more difficult to accelerate or shift smoothly, and causing decreased fuel economy.

What repairs can fix the P0609 code?

Repairing the cause of a P0609 code may take many forms. These include:

  • Inspecting and repairing the electrical components related to the CAN bus.
  • Using a specialty scanner to check the various elements of the CAN bus, to pinpoint the exact issue.
  • Testing control module ground circuits for continuity and repairing any malfunctions.
  • Repairing or replacing faulty PCM drivers.
  • Manually testing the voltage between controller connectors, and repairing open or shorted circuits as necessary.
  • In extreme circumstances, disconnecting all control modules and testing for continuity.

Need help with a P0609 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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