Transmission Fluid Pressure Sensor/Switch A Circuit Range/Performance Problem
The transmission fluid pressure sensor is reporting a value outside expected range.
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What it means (plain English)
Inside the transmission, there's a sensor that measures fluid pressure to help the computer adjust shifting. If the pressure is too low or too high, the sensor throws a code because it's not working right.
What the computer is actually seeing
The transmission control module (TCM) expects the sensor to report fluid pressures in a typical range, usually between 40 to 90 psi when the engine is running. If readings fall outside that range, it throws the P0842 code to signal a fault.
What a healthy reading looks like
Expected fluid pressure range is typically 40-90 psi under normal operating conditions, but can vary by vehicle.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Inspect the transmission fluid level. Ensure it's at the correct level as specified by the manufacturer.
- 22. Check wiring and connectors to the transmission fluid pressure sensor for damage or corrosion. Repair any issues found.
- 33. Using a scan tool, check the live data for fluid pressure readings while the engine is running. Compare to expected values.
- 44. If readings are out of range, replace the transmission fluid pressure sensor and retest the system.
- 55. If the code returns, inspect or replace the TCM if necessary.
Common causes
- Faulty transmission fluid pressure sensor
- Wiring issue or short to ground
- Low transmission fluid level
- Faulty transmission control module (TCM)
- Debris in the transmission fluid
- Poor electrical connections
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's advisable to fix this soon as it can lead to poor shifting and potential transmission damage.
Will this code come back after clearing?
If the underlying issue isn't fixed, the code is likely to return after clearing.
Why does this code pair with other codes?
Transmission issues can have multiple symptoms; other codes may indicate related problems like low fluid or sensor failures.
Working a real vehicle right now?
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