If your Honda Pilot’s check engine light is on and you see the code P0842, you’re in the right place. This article covers everything about the P0842 Honda Pilot error code, from what it means to how to fix it.
That little light can cause a lot of stress. But understanding the problem is the first step to solving it. We’ll break it down in simple terms so you can make informed decisions about your vehicle.
Everything About The P0842 Honda Pilot Error Code
The P0842 is a diagnostic trouble code specific to Honda and Acura vehicles. In plain English, it means the Transmission Fluid Pressure Sensor/Switch “B” Circuit is showing a low voltage reading.
This sensor is crucial. It monitors the hydraulic pressure inside your automatic transmission. The car’s computer uses this data to control shift timing and firmness. A faulty signal can lead to performance issues.
What Does This Sensor Actually Do?
Think of your transmission as a complex hydraulic system. It uses fluid pressure to engage different gears. The Transmission Fluid Pressure Sensor (TFPS) “B” acts like a gauge.
It constantly sends voltage signals to the Transmission Control Module (TCM). This tells the computer the real-time pressure. If the signal voltage drops below a certain threshold for a set period, the TCM logs the P0842 code.
Common Symptoms of the P0842 Code
You might notice more than just the check engine light. Here are the typical signs:
- Illuminated Check Engine Light (CEL) or Malfunction Indicator Lamp (MIL).
- Possible illumination of the “D” indicator light flashing on the dashboard.
- Harsh or erratic shifting, especially between 2nd and 3rd gears.
- Transmission slipping or feeling like it’s in the wrong gear.
- Reduced fuel economy due to inefficient shifting.
- In some cases, the transmission may go into a fail-safe or “limp” mode, limiting you to only one or two gears to prevent damage.
Main Causes of the P0842 Code in Your Honda Pilot
Fixing the P0842 code often involves checking a few key areas. The problem is usually electrical or mechanical.
1. Faulty Transmission Fluid Pressure Sensor “B”
This is the most common culprit. The sensor itself can fail internally. Its internal resistor can wear out, leading to an incorrect low voltage signal being sent to the TCM.
2. Damaged Wiring or Connectors
The electrical circuit connecting the sensor to the TCM can be compromised. Look for:
- Wires that are frayed, corroded, or burnt.
- Loose or damaged electrical connectors at the sensor or TCM.
- Pins inside the connector that are bent or pushed out.
3. Low or Degraded Transmission Fluid
This is a critical and often overlooked cause. If the fluid level is low, the pump can’t generate proper pressure. Old, burnt fluid also won’t function correctly and can cause sensor issues.
Always check the fluid first—it’s the simplest and least expensive possibility.
4. Problems with the Transmission Control Module (TCM)
While less common, the computer itself can malfunction. A software glitch or internal fault could cause it to misread a perfectly good signal from the sensor.
5. Serious Internal Transmission Issues
In worst-case scenarios, the low pressure reading might be accurate. A failing transmission pump, clogged filter, or internal leaks can cause genuinely low fluid pressure. This is more expensive to repair.
How to Diagnose the P0842 Code: A Step-by-Step Guide
Safety first! Ensure the vehicle is on a level surface, the parking brake is firmly engaged, and the engine is off and cool before starting.
Step 1: Scan and Record
Use an OBD-II scanner to confirm the P0842 code is present. Clear the code and take the vehicle for a short test drive. If it returns immediately, the problem is active.
Step 2: Check Transmission Fluid Level and Condition
With the engine warmed up and running, shift through all gears and then park. Pull the transmission dipstick, wipe it clean, reinsert it, and check the level. It should be within the “Hot” crosshatch marks.
- Look at the fluid’s color. It should be reddish and translucent. If it’s dark brown/black, smells burnt, or has particles, it needs changing.
- If the level is low, top it up with the correct Honda ATF (usually ATF DW-1 or Z1) and see if the code clears after a drive.
Step 3: Visual Inspection of Wiring and Connector
Locate the Transmission Fluid Pressure Sensor “B”. On most Honda Pilots, it’s on the transmission side. Carefully unplug the electrical connector.
- Inspect for corrosion, dirt, or moisture.
- Check that the pins are straight and clean.
- Follow the wiring harness back a few inches, looking for any obvious damage or chafing.
Step 4: Test the Sensor and Circuit
This step requires a digital multimeter (DMM).
- With the connector disconnected, test the sensor’s resistance across its two terminals. Compare your reading to the manufacturer’s specification (often found in a repair manual). A reading of zero or infinite ohms indicates a bad sensor.
- Next, test the vehicle’s wiring harness. With the connector still unplugged from the sensor, turn the ignition to “ON” (engine off). Check for reference voltage (usually 5V) and ground at the harness connector pins.
- If the wiring checks out but the sensor resistance is off, the sensor is likely faulty.
Step 5: Consider Professional Diagnosis
If the fluid, wiring, and sensor seem okay, the issue could be deeper. A professional mechanic can use a scan tool to monitor live data from the sensor while driving and perform a hydraulic pressure test to rule out internal transmission problems.
Repair Procedures and Estimated Costs
The cost to fix a P0842 code varies widly depending on the root cause.
1. Transmission Fluid Service
If the fluid is just low or dirty, a drain and refill (or a full flush) might solve it.
- DIY Cost: $50 – $150 for fluid and a new filter/pan gasket.
- Shop Cost: $150 – $300.
2. Replacing the Pressure Sensor “B”
This is a common repair. The part is usually accessible from under the vehicle.
- Part Cost: $80 – $200 for a quality OEM or OEM-equivalent sensor.
- DIY Labor: Moderate difficulty. You’ll need basic tools and to handle the electrical connection carefully.
- Shop Labor Cost: 1-2 hours of labor, totaling $250 – $500 for parts and labor.
3. Wiring Harness Repair
If the problem is a broken wire or bad connector.
- Cost: Minimal for a DIY solder and seal repair. A shop might charge 1 hour of labor ($100-$150) plus parts for a new connector.
4. Major Transmission Repair
If internal damage is confirmed (e.g., failed pump, valve body issues), costs rise significantly.
- Cost: This can range from $1,500 for a valve body replacement to $3,500+ for a full transmission rebuild or replacement.
Can You Drive Your Honda Pilot with the P0842 Code?
This is not recommended for the long term. If the transmission is shifting normally, a short drive to a mechanic or parts store is probably low-risk.
However, if you notice harsh shifting, slipping, or the vehicle is in limp mode, you should avoid driving it. Continuing to drive can cause further, more costly damage to the transmission internals. It’s best to adress the issue promptly.
Prevention Tips
Regular maintenance is key to avoiding this and other transmission codes.
- Follow Honda’s recommended service intervals for transmission fluid changes. For many Pilots, this is every 30,000 to 60,000 miles under severe use.
- Periodically check your transmission fluid level and condition (every few oil changes is a good habit).
- Address any minor shifting concerns early, before they trigger fault codes.
- Be gentle on your transmission—avoid aggressive towing without proper cooling and harsh acceleration.
FAQ Section
Is P0842 a serious code?
It can be. While sometimes it’s a simple sensor or fluid issue, it can indicate serious internal transmission problems. It should be diagnosed promptly.
What does Transmission Fluid Pressure Sensor Switch B Circuit Low mean?
This is the full definition of the P0842 code. It means the vehicle’s computer is seeing a lower-than-expected voltage signal from the specific sensor (“B”) that monitors transmission fluid pressure.
Will P0842 cause my Pilot to go into limp mode?
It can, especially if the computer detects a condition that could damage the transmission. Limp mode protects the gearbox by restricting gear changes.
Can a bad battery cause a P0842 code?
It’s very unlikely. While low system voltage can cause strange electrical issues, the P0842 is too specific. The problem is almost always in the sensor’s circuit or the transmission system itself.
How do I clear the P0842 code?
You can clear it with an OBD-II scanner. But if you don’t fix the underlying problem, the code and check engine light will simply come back, usually after one or two drive cycles.
Dealing with a P0842 code in your Honda Pilot can be manageable. Start with the simple checks: fluid level and condition, followed by a visual wiring inspection. For many owners, replacing the Transmission Fluid Pressure Sensor “B” resolves the issue. If the problem seems more complex, consulting a trusted mechanic for a professional diagnosis is the smartest course of action to protect your vehicle’s transmission.