P0840: Transmission Fluid Pressure Sensor/Switch A Circuit
What Does P0840 Mean?
P0840 is a diagnostic trouble code indicating: Transmission Fluid Pressure Sensor/Switch A Circuit. This code relates to the transmission system. It has been reported in NHTSA complaints across 2 different vehicle models.
Symptoms of P0840
- ⚠️ Check engine light illuminated
P0840 Reports by Year
Real Owner Reports
From NHTSA complaint database — actual owner descriptions.
"CVT NEEDS REPLACEMENT! TIME TO STAND BY NISSAN PRODUCTS AND CUSTOMERS. CODES ARE ALL TRANSMISSION RELATED, P0774, P0840, P0845, P1778. VIN [XXX]. THEY ARE HIDING BEHIND 10 YR OR 120,000 MILE WALL. 06 MURANO HAS 94,000 MILES. BEING PUNISHED FOR DRIVING LESS THAN 8,000 MILES PER YEAR. THIS MODEL NEE"
— Nissan Murano owner, 05/02/2018
"Check engine light came on with sudden decrease in power. Code is P0840. Car is an 09, but has only 96k miles."
— Nissan Altima owner, 12/15/2022
Source: NHTSA Complaints Database
Most Reported Vehicles for P0840
Based on NHTSA owner complaint data.
| # | Vehicle | Reports |
|---|---|---|
| 1 | NISSAN ALTIMA | |
| 2 | NISSAN MURANO |
Frequently Asked Questions
Is it safe to drive with this transmission code?
Do I need a full transmission rebuild?
How much does a transmission repair cost?
What To Do Next
Possible Fixes
- 🔧 Have the code scanned with a professional-grade scanner to read freeze frame data
- 🔧 Check transmission fluid level and condition; top off or change if needed
- 🔧 If DIY repair isn't feasible, get a diagnostic from a trusted mechanic ($50-150)
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Find your vehicle above
Click your make and model for real owner reports and common causes specific to your vehicle.
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Check for recalls
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.
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Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.