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P0843: Transmission fluid pressure sensor/switch A: circuit high

The control unit gets too high a voltage from gearbox fluid pressure sensor A. An open wire, the connector or the sensor is the usual cause.

Code P0843 at a glance
CodeP0843
SystemEngine and transmission
GroupP08xx, Transmission
TypeGeneric: it means the same on every make
Can you keep driving?With care

What P0843 means

The gearbox fluid pressure sensor reports to the control unit through a voltage. Here that voltage is above the possible range, typical of an open circuit or a short to positive rather than genuinely high pressure. What sensor A is is decided by each manufacturer.

Most common causes

  • Sensor connector unplugged or with open pins
  • Broken sensor earth wire
  • Signal wire touching a positive feed
  • Faulty pressure sensor or switch itself
  • Gearbox control unit fault (rare)

Symptoms

  • Engine or gearbox warning light on
  • Gearbox in limp mode
  • Harsh shifts

Can you drive with P0843?

With care You can drive carefully, but the gearbox may restrict gears. Best to get it to a garage soon.

How to check it

Make sure the sensor connector is fully seated with no bent pins. If the live value sits at maximum all the time, an open circuit is almost certain.

How to read and clear P0843 with Final OBD

Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0843 with this same explanation and whether it’s confirmed, pending or permanent.

This code is usually stored by the gearbox control unit. With Free you read it for nothing with its short description, because Free reads every control unit; with Pro you also get the full explanation, how the car was running when it was logged and clearing.

Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before the ITV. It’s all in how to read and clear fault codes and in the ITV and OBD.

Similar codes

P0843 is a generic code, so it means the same on any make, for example on BMW, Ford, Mercedes-Benz, Renault, Volkswagen, Volvo. See what Final OBD does on your car in makes and models.

What does code P0843 mean?

The gearbox fluid pressure sensor reports to the control unit through a voltage. Here that voltage is above the possible range, typical of an open circuit or a short to positive rather than genuinely high pressure. What sensor A is is decided by each manufacturer.

Can you drive with P0843?

You can drive carefully, but the gearbox may restrict gears. Best to get it to a garage soon.

How do you clear P0843?

With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0843 comes back.