OBD-II P0842 Error Code: How to Fix Trans Fluid Pressure Sensor A Low

Medium 1-2 hours Medium Severity Verified June 2026
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Error Code
P0842
Brand
OBD-II Generic
Product Type
automotive
Severity
Medium
DIY Difficulty
Medium
Estimated Fix Time
1-2 hours
Error code P0842 indicates that the transmission fluid pressure sensor or switch A is reading lower than expected. This can lead to harsh shifting or limp mode. The issue is often a faulty sensor, low fluid, or a wiring problem.
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Tools You'll Need

How to Fix Error Code P0842

  1. Check Transmission Fluid Level and Condition

    Engine components are hot; let engine cool slightly before checking.

  2. Inspect Wiring and Connectors for Damage

    Disconnect the battery negative terminal before working on electrical components.

  3. Test the Pressure Sensor with a Multimeter

  4. Clear the Error Code and Test Drive

    Ensure all repairs are complete before clearing the code.

Parts You May Need

Transmission fluid pressure sensor
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Transmission fluid
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Wiring repair kit
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Transmission fluid pressure sensor
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Transmission fluid
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Wiring repair kit
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Transmission fluid pressure sensor
Check Price on Amazon
Transmission fluid
Check Price on Amazon
Wiring repair kit
Check Price on Amazon
Transmission fluid pressure sensor
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Transmission fluid
Check Price on Amazon
Wiring repair kit
Check Price on Amazon
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When to Call a Professional

If you have checked fluid, wiring, and the sensor, and the code persists, or if internal transmission damage is suspected (e.g., grinding noises, slipping), consult a professional mechanic.

Frequently Asked Questions

Can I drive with code P0842?
It's not recommended. Low pressure can cause harsh shifting or transmission damage. Drive only to a repair shop if necessary.
Is P0842 a serious error?
Yes, it can lead to transmission failure if ignored. The severity is medium to high.
How much does it cost to fix P0842?
Cost varies: sensor replacement $100-$300, wiring repair $100-$500, or fluid change $100-$200. Diagnosis may add $50-$150.
Will a bad sensor cause shifting problems?
Yes, a faulty sensor can cause incorrect pressure readings, leading to harsh or delayed shifts.
Can low transmission fluid cause code P0842?
Absolutely. Low fluid reduces hydraulic pressure, which the sensor detects as low. Always check fluid first.

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