What Does P0842 Mean?
The TCM has detected that the voltage from the transmission fluid pressure sensor/switch "A" circuit is below the minimum allowable threshold. This low signal condition typically indicates the sensor is shorted internally, the wiring has a short to ground, or the connector has a low-resistance fault. The TCM will default to a substitute pressure value.
Common Causes
35%
Internally shorted transmission fluid pressure sensor A
30%
Short to ground in the sensor A signal wire
20%
Corroded or contaminated connector creating low-resistance path
10%
Transmission fluid contamination affecting sensor element
5%
TCM reference voltage circuit fault
Diagnostic Steps
1
Verify the pressure sensor A PID reads near-zero voltage, confirming the low circuit condition.
2
Disconnect the pressure sensor A connector; if the signal voltage at the TCM rises to reference voltage (typically 5V), the sensor is shorted internally.
3
Measure the sensor resistance and compare to factory specs — abnormally low resistance confirms sensor failure.
4
With the sensor disconnected, test the signal wire for continuity to ground; there should be none.
5
Check the internal transmission harness connector for signs of fluid intrusion or corrosion.
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 below the minimum allowable threshold. This low signal condition typically indicates the sensor is shorted internally, the wiring has a short to ground, or the connector has a low-resistance fault...
The most common cause of P0842 (Transmission Fluid Pressure Sensor/Switch "A" Circuit Low) is: Internally shorted transmission fluid pressure sensor A
Typical repair costs for P0842 range from $200 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The transmission will use default pressure values, resulting in potentially harsh shifts and degraded performance. Drivable for short distances but should be repaired soon to prevent transmission wear.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0842 to identify the root cause.
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Quick Info
Category
Powertrain
System
Automatic Transmission
Difficulty
Type
Generic (SAE)
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