What Does P0843 Mean?
The TCM has detected that the voltage from the transmission fluid pressure sensor/switch "A" circuit is above the maximum allowable threshold. This high signal condition indicates an open sensor, disconnected connector, broken wire, or short to voltage. Without valid pressure feedback, the TCM cannot optimally control shift quality.
Common Causes
35%
Open or failed transmission fluid pressure sensor A
25%
Disconnected or loose sensor connector
20%
Open circuit in signal wire between sensor and TCM
15%
Short to voltage in the signal wire
5%
TCM connector fault
Diagnostic Steps
1
Confirm the pressure sensor A PID reads at or near maximum voltage (approximately 5V), verifying the high circuit condition.
2
Check that the sensor connector is properly seated — it may have been left disconnected after recent transmission service.
3
Measure the sensor resistance; an open/infinite reading indicates the sensor has failed.
4
With the sensor disconnected, check the signal wire for a short to voltage using a multimeter.
5
Verify wire continuity from the sensor connector to the TCM for the signal, ground, and reference circuits.
Estimated Repair Cost
$200 - $800
Parts + labor, varies by vehicle and location
The TCM has detected that the voltage from the transmission fluid pressure sensor/switch "A" circuit is above the maximum allowable threshold. This high signal condition indicates an open sensor, disconnected connector, broken wire, or short to voltage. Without valid pressure feedback, the TCM canno...
The most common cause of P0843 (Transmission Fluid Pressure Sensor/Switch "A" Circuit High) is: Open or failed transmission fluid pressure sensor A
Typical repair costs for P0843 range from $200 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Shift quality will suffer and the transmission may enter limp mode with limited gear availability. The vehicle can be driven short distances but repair is needed to prevent internal damage from unmonitored pressure.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0843 to identify the root cause.
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Quick Info
Category
Powertrain
System
Automatic Transmission
Difficulty
Type
Generic (SAE)
Recommended Tools
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