Transmission Fluid Pressure Sensor/Switch A Circuit Low
The P0842 code means the vehicle's onboard diagnostic system has detected: Transmission Fluid Pressure Sensor/Switch A Circuit Low. This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- hard
- Estimated cost
- $100 - $500 (parts and labor)
Read and clear transmission codes. Many trans codes are caused by low or burnt fluid -- check level and color before assuming the worst.
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Basic scanners only read engine codes. This reads transmission, ABS, and airbag too.
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Common Symptoms
- Check Engine Light illuminated
- Transmission slipping or flaring on shifts
- Delayed engagement into drive or reverse
- Vehicle may enter limp mode
Probable Causes (Ranked by Likelihood)
- Short to ground in pressure sensor A signal wire Very High
- Faulty pressure sensor A with low output High
- Corroded connector at pressure sensor A Moderate
- Extremely low transmission fluid level Moderate
Step-by-Step Diagnostic Procedure
-
Check transmission fluid level immediately
-
Measure voltage at the pressure sensor A connector
-
Test for short to ground on the signal wire
-
Replace sensor A if connector and wiring are confirmed good
Frequently Asked Questions
Is low pressure dangerous for my transmission?
Yes, operating with low transmission fluid pressure can cause clutch slippage and overheating, which leads to premature wear and possible transmission failure.
Could a transmission fluid leak cause P0842?
Yes, a leak that lowers the fluid level enough will reduce line pressure, which the sensor reports as a low reading.
How much does a pressure sensor cost?
The sensor itself is typically $30 to $100. Labor varies depending on its location, with easily accessible sensors costing less to replace.
Sources
This page is built from documented references. Verify against your own service info before repair work.
P0842 on Diesel, EV & Equipment
The same code ID appears across other engines and platforms. The diagnostic flow varies by manufacturer — these are the platform-specific breakdowns:
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