If your Honda’s check engine light is on and the scanner shows P0848, you’re likely looking for answers. This article explains the P0848 Honda error code causes, symptoms, and fixes to help you understand what’s wrong.
It’s a transmission-related code that shouldn’t be ignored. Let’s break down what it means for your vehicle and what you can do about it.
P0848 Honda Error Code Causes, Symptoms, and Fixes
The P0848 code is specific to Honda and Acura vehicles. It stands for “Transmission Fluid Pressure Sensor/Switch ‘B’ Circuit High.”
In simpler terms, your car’s computer (the PCM) is reading a voltage signal from a specific transmission fluid pressure sensor that is higher than expected. This sensor, often called Switch B or the 3rd Clutch Pressure Switch, monitors hydraulic pressure inside the transmission.
When the signal is too high, the PCM triggers the P0848 code and illuminates the check engine light.
What Does the Transmission Fluid Pressure Sensor Do?
Your automatic transmission is a complex hydraulic system. It uses pressurized fluid to engage different gear clutches and bands.
The pressure sensors are like reporters. They tell the PCM the exact fluid pressure in key circuits. The PCM uses this data to control shift timing, firmness, and the lock-up torque converter.
Sensor ‘B’ typically relates to the pressure for the 3rd or 4th gear clutch pack. A faulty signal disrupts the PCM’s ability to manage shifts properly.
Common Symptoms of a P0848 Code
You might notice one or more of these signs when P0848 is active:
- Illuminated Check Engine Light: This is the primary alert. The light may be solid, but if driving issues are severe, it could blink.
- Harsh or Slipping Shifts: You may feel rough jerks during gear changes, especially into 3rd or 4th gear. The transmission might also slip, causing a surge in RPMs without acceleration.
- Poor Fuel Economy: Inefficient shifting can lead to worse gas mileage.
- Transmission Goes into “Limp Mode”: To prevent damage, the PCM may lock the transmission in a single gear (usually 2nd or 3rd). You’ll have very limited power and speed.
- Delayed Shifts or Gear Hunting: The transmission may hesitate before shifting or constantly shift up and down.
Main Causes of the P0848 Error Code
Finding the root cause is key to a proper repair. Here are the most likely culprits:
1. A Faulty Transmission Fluid Pressure Sensor
This is the most common cause. The sensor itself can fail internally. Electrical components wear out over time due to heat and vibration inside the transmission.
A failed sensor sends an incorrect high voltage signal, tripping the code.
2. Problems in the Sensor’s Electrical Circuit
The issue might not be the sensor, but its wiring. Look for:
- Damaged, frayed, or corroded wires to the sensor.
- A poor electrical connection at the sensor plug or PCM.
- A short to power in the circuit, causing the voltage to read high.
3. Low or Degraded Transmission Fluid
Low fluid level can cause low pressure, but the sensor might read this condition erratically, leading to a high voltage signal. Old, burnt fluid loses its properties and can’t maintain proper pressure.
Contaminants in the fluid can also clog the sensor’s port.
4. Serious Internal Transmission Issues
While less common, mechanical problems can cause P0848. A clogged filter, failing pump, or internal leaks in the 3rd clutch circuit can create abnormal pressure.
The sensor might be correctly reporting a genuine pressure problem caused by mechanical failure.
How to Diagnose and Fix P0848
Fixing P0848 often requires mechanical skill. If you’re not comfortable, consult a professional. Here’s a step-by-step guide to the process.
Step 1: Scan and Record Codes
Use an OBD-II scanner to confirm P0848 is present. Note any other codes. Codes like P0847 or P0849 point to the same sensor circuit and help confirm the diagnosis.
Clear the code and take a test drive to see if it returns immediately or only under certain conditions.
Step 2: Check the Transmission Fluid
This is a critical and easy step. With the engine warm and running, and the car on level ground, check the transmission dipstick.
- Is the fluid at the correct “Hot” level on the dipstick?
- What does the fluid look and smell like? Fresh fluid is red or pink and has a slightly sweet smell. Burnt fluid is dark brown/black, smells burnt, and may have particles.
Top up with the correct Honda ATF (like ATF-Z1 or DW-1) if low. If fluid is burnt, a fluid change may be needed, but diagnose further first.
Step 3. Inspect Wiring and Connections
Locate the transmission pressure sensor (usually on the transmission valve body, accessible from the side or top).
Carefully unplug the electrical connector. Look for:
- Corrosion or moisture on the pins.
- Bent or pushed-out pins.
- Damage to the wires leading back from the plug.
Repair any damaged wires and clean any corrosion. A poor connection here is a frequent fix.
Step 4: Test the Sensor and Circuit
This requires a digital multimeter. You’ll need to test the sensor’s resistance and check for power and ground in the harness.
Refer to a service manual for your specific Honda model for exact testing procedures and values. A faulty sensor will typically show an out-of-spec resistance reading.
Step 5: Replace the Pressure Sensor
If wiring is good and the sensor tests bad, replacement is the next step. The sensor often screws into the transmission case.
- Disconnect the negative battery terminal for safety.
- Unplug the electrical connector.
- Unscrew the old sensor. Be prepared for some fluid loss—have a drain pan ready.
- Install the new sensor with a new sealing washer or O-ring. Tighten to the specified torque.
- Reconnect the plug and battery.
- Clear the code, start the engine, check fluid level again, and test drive.
Step 6: Address Internal Transmission Problems
If the code returns after replacing a known-good sensor and verifying the circuit, the problem is likely internal. This could involve:
- Replacing the transmission filter and performing a full fluid flush.
- Inspecting the valve body for stuck valves.
- Diagnosing the hydraulic pump or internal clutch seals.
These repairs are complex and usually require removing the transmission. Seek a reputable transmission specialist at this stage.
Estimated Repair Costs
Costs vary widely based on the cause and your location.
- Transmission Fluid Change/Top-Up: $100-$200.
- Pressure Sensor Replacement: $150-$400. The part is relatively inexpensive ($50-$150), but labor involves accessing the sensor.
- Wiring Harness Repair: $100-$300, depending on complexity.
- Major Internal Repair: $1,500-$3,500+ if a valve body, pump, or clutch overhaul is needed.
Diagnosis is key to avoiding unnecessary repairs. A good mechanic will test the sensor and circuit before recommending major work.
Can You Drive with a P0848 Code?
It’s not recommended. While you might be able to drive for a short distance, the risk is significant.
If the transmission enters limp mode, you’ll be stranded. More importantly, driving with incorrect pressure can cause rapid wear or catastrophic failure of internal clutch packs, leading to a much more expensive repair.
Address the code as soon as possible to prevent further damage.
FAQs About the P0848 Honda Code
Is P0848 a serious code?
Yes, it can be. It indicates a problem with the transmission’s hydraulic pressure control. Ignoring it can lead to transmission damage.
What does ‘Circuit High’ mean in P0848?
It means the voltage signal from the sensor to the computer is reading higher than the normal expected range. This usually indicates a faulty sensor, a wiring short, or a genuine high-pressure condition.
Will P0848 cause my transmission to fail?
It can if left unfixed. The computer relies on the sensor data to control shifts. Bad data can cause harsh shifting, slippage, and overheating, which all contribute to premature failure.
Can I reset the P0848 code myself?
You can clear it with an OBD-II scanner, but it will return if the underlying problem isn’t fixed. Clearing the code can turn off the check engine light and exit limp mode temporarily, but it’s not a fix.
Are there other codes related to P0848?
Yes. P0847 (Circuit Low) and P0849 (Circuit Intermittent) are for the same sensor. Seeing these together often points to the sensor or its wiring.
Prevention Tips
While sensor failure isn’t always preventable, you can maintain your transmission health.
- Follow your Honda’s recommended service intervals for transmission fluid changes. This is often around every 60,000 miles, but check your manual.
- Use only the type of automatic transmission fluid specified for your model. The wrong fluid can cause shifting problems and sensor issues.
- Avoid harsh driving habits like “rocking” the car when stuck or aggressive towing beyond your vehicle’s capacity.
- Address any other transmission symptoms, like slight hesitation, promptly. Small problems can lead to bigger ones.
Remember, the P0848 code is your car’s way of asking for help. Taking quick, informed action can save you time, money, and the hassle of a major breakdown. Start with the simple checks—fluid level and wiring—before moving to sensor replacement or internal repairs. With a methodical approach, you can get your Honda shifting smoothly again.