The OBD2 code P0848 indicates a problem with the transmission fluid pressure sensor/switch “B” circuit, signaling that the circuit is experiencing high input. This sensor is crucial for monitoring the hydraulic fluid pressure in the transmission and helps the vehicle’s computer to adjust shifts accurately.
P0848 quick overview
| Meaning | P0848: Transmission Fluid Pressure Sensor/Switch “B” Circuit High |
| Is it serious? | Yes, it can lead to transmission shifting issues and may affect the vehicle’s performance. |
| Possible causes | – Faulty 3rd clutch transmission fluid pressure switch – Wiring or connector issues in the circuit – Poor ground connection – Potential PCM (Powertrain Control Module) issues |
| How to diagnose? | Check the associated ground for the circuit for any issues. Ensure the correct switch was replaced and verify wiring integrity. Verify tightness of pin fits in connectors. Consider PCM issues, but explore all other options first. |
P0848 Meaning
For those not deeply familiar with automotive mechanics, the transmission fluid pressure sensor acts somewhat like a detective, constantly monitoring the pressure of the fluid that helps change gears in your car. If this sensor or its circuit sends a signal that’s too “high” or abnormal, it’s like getting incorrect clues that lead to the car’s computer making wrong decisions about shifting gears.
This can result in the car not driving smoothly, or in some cases, not being able to engage gears properly. Fixing this issue usually involves checking and possibly replacing the sensor, along with ensuring all electrical connections are correct and secure.
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How to fix P0848 – learn from mechanics
I looked into P0848 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.
Case #1: Honda
Vehicle information 2007 Honda Accord EX 3.0L
Issue + repair history
- P0848 code: Open in 3rd Clutch Transmission Fluid Pressure Switch Circuit or 3rd Clutch Transmission Fluid Pressure Switch Stuck OFF
- Replaced 3rd clutch transmission pressure switch initially
- Continued issue with blinking “D” indicator after switch replacement
Other OBD2 Codes + Test Results
- P0848
Mechanic suggestions
- Check the associated ground for the circuit first, as battery voltage on a 5-volt circuit could indicate an open or corroded ground
- Ensure correct switch was replaced and check wiring by grounding out the wire and observing data on the scan tool to see if it switches
- Verify tightness of pin fits
- Consider purchasing a PCM, but explore options for flashing and availability at local parts stores
Final fix
- Issue resolved by replacing the defective switch with a new one recommended by the Honda parts department
Case #2: Chevrolet
Vehicle information 2003 Chevrolet C4500 Kodiak C4C042 8.1L
Issue + repair history
- Truck wouldn’t engage drive or reverse after differential rebuild and fixing leaky rear main seal
- Unable to pull codes initially
- Acquired TECH 2 to diagnose, found no ground at pin 4 of ALDL connector
- Applied ground to circuit and TECH 2 powered up
- Retrieved and cleared multiple codes including: P0843, P0847, P0848, P0871, P0875
- Additional codes appeared when gears were not engaged: P0872, P0873, P0875
Other OBD2 Codes + Test Results
- P0843
- P0847
- P0848
- P0871
- P0875
Mechanic suggestions
- Check for cooler flow to ensure the pump is not broken
- Replace MLPS (PRND switch) if working on an Allison transmission as it is a common failure item causing no movement conditions
- Provide detailed information about the transmission type and code definitions when seeking help
Final fix
- Replacing the MLPS resolved all codes, including non-transmission related ones, and ensuring proper fluid level allowed the unit to engage gears properly. The use of a TECH2 scan tool was crucial in diagnosing and fixing the issue.
Case #3: Nissan
Vehicle information 2012 Nissan Versa 1.6 S 1.6L
Issue + repair history
- Initially came in for a P0744 TCC solenoid code
- Erratic transmission behavior led to transmission replacement
- Replaced valve body, TCM, and tried multiple transmissions, including new and rebuilt units
- Transmission failed to engage properly and returned codes P0846 and P0965
- Multiple attempts at reprogramming and diagnosis, including testing wiring and circuits related to the issue
- Four transmission replacements in total
- Final resolution involved using the original valve body with a new wiring harness
Other OBD2 Codes + Test Results
- P0848
- P0744: Failed converter solenoid
- P0846: Transmission sensor B
- P0965: Tested wiring, satisfactory results
Mechanic suggestions
- Consider using OEM parts or dealer transmissions for better compatibility
- Ensure proper fluid quality, as many Nissan CVT issues are related to fluid condition
- When resetting CAL IDs, use Autel or Nissan software for better compatibility
- Check for CD shipment with trans, as EEPROM location may affect programming success
Final fix
- Used original valve body with a new wiring harness to resolve the issue. Despite attempts with multiple transmissions and TCM replacements, the solution was found in using the original valve body with updated wiring.
Detail from mechanic: important things I can leave you with are that if you have a p0848 you can not set the clutch point relearn. When diagnosing this code it leads to a replace transmission required ending. I have now done that 4 times. I am right now hoping that they have a program that will get this trans to work.
How to diagnose P0848
I made you an overview of solving this DTC, based on all the advice that was suggested by certified mechanics to address this issue in previously mentioned service cases.
| Diagnostic Step | Brief Explanation |
|---|---|
| Check associated ground for the circuit | A faulty ground can lead to incorrect voltage readings, mimicking sensor failure. |
| Ensure correct switch replacement | Incorrect parts can cause recurring issues; always double-check the replaced component. |
| Verify wiring and connector integrity | Damaged wires or loose connectors can disrupt sensor function, leading to false code triggers. |
| Replace defective switch with OEM recommendation | Using parts recommended by the manufacturer ensures compatibility and often resolves the issue. |
| Consider PCM evaluation | If all else fails, the issue might be within the vehicle’s computer system, requiring professional diagnosis. |
These service cases underscore the importance of thorough diagnostics, including checking electrical connections, ensuring the use of correct and OEM-approved parts, and considering all possible causes before moving towards more invasive and costly solutions like PCM replacement. Proper diagnostics, including ground checks, wiring integrity verification, and careful part selection, are critical to resolving P0848 effectively.
Car Diagnostics Training
- Car Electrical basics
- OBD-II scanner basics
- How to use an OBD reader
- Introduction to a Bi-directional Scan tool
- OBD scanner buyer’s guide + discounts
I test OBD-II scanners and make DIY Engine diagnostics guides to help you solve your car problems without having to depend on the mechanic. A lot of them will try to scam you or are just no help at all. About Juraj Lukacko