If your Honda’s check engine light is on and you’ve found the code U0155, you’re likely wondering what’s wrong. The Honda U0155 error code is a communication problem that needs your attention.
This code means your car’s main computer isn’t talking properly with the instrument cluster. It’s a network issue, not usually a sign of immediate mechanical failure. But it can affect your gauges and warning lights, which is a safety concern.
Let’s look at what causes this code and how you can fix it yourself.
Honda U0155
This code is specific to the communication network inside your Honda. Modern cars use a network, like the one in your home or office, to let modules talk to each other.
The U0155 code sets when the Powertrain Control Module (PCM) loses communication with the instrument panel control module. This happens for a set amount of time, usually a few seconds.
Your speedometer, tachometer, fuel gauge, and warning lights may act strange or not work at all. The car will still run, but you won’t have vital driving information.
Common Symptoms of the U0155 Code
You’ll usually notice more than just a check engine light. Here are the signs to watch for:
- Check engine light is illuminated (this is how you got the code).
- Malfunction Indicator Lamp (MIL) might also be on.
- Gauges on the instrument cluster are dead or behaving erratically (e.g., fuel gauge shows empty when full, speedometer at zero while driving).
- Warning lights (like battery, oil pressure) may not light up during the bulb check when you start the car.
- The odometer or trip meter display may be blank or frozen.
- In some cases, the entire instrument cluster screen may be black.
Main Causes of the U0155 Diagnostic Trouble Code
The root cause is always a break in communication. Here are the most likely culprits, starting with the simplest:
- Blown Fuse: A fuse powers the instrument cluster or the communication network. This is the easiest thing to check first.
- Faulty Instrument Cluster: The cluster itself can fail internally. This is a common issue in some Honda models.
- Wiring Harness Issues: Wires can get damaged, corroded, or have loose connections. This includes the specific communication wires (CAN bus lines) that connect the PCM to the cluster.
- Problems with the PCM: While less common, the engine computer itself could have an internal fault causing it to drop off the network.
- Low Battery Voltage: A weak or dying battery can cause all sorts of strange electrical and communication glitches in modern vehicles.
Tools You Will Need for Diagnosis
Gathering the right tools before you start will make the job smoother. You won’t need everything for every check.
- A basic OBD-II code scanner (the one you used to get the U0155 code).
- A digital multimeter (DMM) for checking voltage, continuity, and resistance.
- A set of automotive fuses for replacement.
- A wiring diagram for your specific Honda model and year (you can often find these online).
- Basic hand tools: screwdrivers, trim removal tools, socket set.
- Electrical contact cleaner.
- Dielectric grease for reconnecting connectors.
Step-by-Step Diagnostic and Fix Guide
Follow these steps in order. They start with the easiest and least expensive checks.
Step 1: Check and Reset the Code
First, write down any other codes present. Then, clear the U0155 code with your scanner. Turn the ignition off and on, and take the car for a short drive.
See if the code returns immediately. If it doesn’t come back, it might have been a temporary glitch caused by low voltage or a loose connection that jiggled back into place.
Step 2: Inspect the Battery and Charging System
A weak electrical system causes countless network errors. Use your multimeter to check battery voltage.
- With the car off, it should be at least 12.4 – 12.6 volts.
- With the engine running, it should be 13.5 – 14.5 volts, indicating the alternator is charging properly.
If voltage is low, charge or replace the battery and retest. Clean any corrosion from the battery terminals too.
Step 3: Locate and Check All Related Fuses
Consult your owner’s manual or a fuse diagram to find the fuses for:
- Instrument Panel
- Meter
- ECU/PCM
- Backup
- Any fuse related to the “CAN System” or “Communication Network”
Visually inspect each fuse, or use the multimeter’s continuity setting to check them. Replace any that are blown. This simple fix solves the problem more often than you’d think.
Step 4: Visually Inspect Wiring and Connectors
This step requires some patience. You need to access the wiring behind the instrument cluster and, if possible, near the PCM.
- Disconnect the negative battery cable for safety.
- Carefully remove the trim around the instrument cluster, then the cluster itself. Refer to a service manual for your model to avoid breaking clips.
- Inspect the large connector on the back of the cluster. Look for bent, pushed-out, or corroded pins.
- Trace the wiring harness you can see for any obvious damage, chafing, or burnt spots.
- Check connectors at the PCM (usually under the hood). Look for corrosion or moisture.
Spray any dirty connectors with electrical contact cleaner and let them dry completely before reconnecting.
Step 5: Perform a Network Communication Test
This is where a scanner with advanced capabilities helps. A basic code reader might not work for this.
A professional-grade scanner can often perform an active test on the instrument cluster, like lighting up all the warning lights on command. If it can’t communicate to run the test, it confirms the network break.
It can also check live data from other modules to see if the network as a whole is functioning.
Step 6: Test Wiring with a Multimeter
If you have a wiring diagram, you can check the specific CAN communication wires. This is more advanced.
- Set your multimeter to measure resistance (Ohms).
- With key off and connectors disconnected, check for continuity on the CAN wires between the PCM connector and the cluster connector. There should be very low resistance (close to 0 Ohms).
- Check for a short to power or ground. There should be infinite resistance between the CAN wire and battery positive or negative.
A reading of infinite resistance on a continuity check means the wire is broken. A low resistance reading to ground or power means it’s shorted.
Step 7: Address the Faulty Component
Based on your findings, you can now address the root cause:
- Fixed Fuse: If a blown fuse was the issue, monitor it. If it blows again, you have a deeper wiring short that needs fixing.
- Repaired Wiring: Solder and heat-shrink any broken wires you found. Properly repair any shorts.
- Faulty Instrument Cluster: This is a common fix. You have two options:
- Replace with a New Unit: This is expensive but guaranteed.
- Send for Professional Repair: Many companies specialize in repairing instrument clusters at a fraction of the new cost. They can often fix the internal circuit board fault.
- Replace with a Used Unit: If you go this route, ensure it’s from the exact same model, year, and trim. Used clusters may need to be professionally programmed to your vehicle’s VIN and mileage.
- Faulty PCM: This is rare. It requires professional diagnosis and likely programming by a dealer or specialist.
Preventing the U0155 Code from Returning
Once fixed, keep the problem from coming back with good habits.
- Maintain your battery. Replace it when it gets weak (typically every 4-5 years).
- Avoid causing voltage spikes. Don’t jump-start other cars with your Honda, and be careful when charging the battery.
- When doing any electrical work, always disconnect the negative battery terminal first.
- If you had a wiring issue, secure the repaired harness properly so it doesn’t chafe or get pinched again.
When to See a Professional Mechanic
Don’t hesitate to get help if:
- You’re uncomfortable removing the instrument cluster or testing wiring.
- You’ve done all the basic checks (fuses, battery) and the code persists.
- You suspect the PCM is at fault.
- The repair requires specialized programming of a new cluster or PCM.
- You don’t have access to a professional-grade scan tool for network testing.
A good independent shop or the dealership will have the tools and diagrams to diagnose this efficiently.
Frequently Asked Questions (FAQ)
Is it safe to drive my Honda with a U0155 code?
You should avoid driving it if possible. While the engine will run, not having functional gauges (like speed or warning lights for oil/battery) is a major safety risk. You won’t know if a critical problem occurs.
Can a U0155 code cause my car not to start?
Typically, no. The U0155 code itself is a communication fault, not an immobilizer or starter issue. However, the underlying cause—like a severely drained battery or a major short affecting multiple systems—could prevent starting.
How much does it cost to fix a Honda U0155 code?
The cost varies widly:
- Fuse Replacement: A few dollars.
- Wiring Repair: $100 – $300 depending on labor time.
- Instrument Cluster Repair: $200 – $400 for a repair service.
- New Instrument Cluster: $500 – $1000+ plus programming labor.
- Dealer Diagnosis: Usually 1 hour of labor ($100 – $200) just to start.
Can I just ignore the U0155 code if my gauges are working?
No. The code means communication was lost, even if it seems intermittent. The problem could worsen, leading to a complete cluster failure at an inconvenient time. It’s best to diagnose it while things are partly working.
Are there other codes that often appear with U0155?
Yes. You may see other U-series network codes (like U0100, U0151, etc.) pointing to communication loss with other modules. This often indicates a network-wide issue like a bad fuse, wiring fault at a common junction, or low system voltage affecting everything.
Fixing the Honda U0155 error code is very doable with a methodical approach. Start with the simple checks like the battery and fuses. Often, the solution is straightforward. Even if it leads to a cluster repair, understanding the cause saves you time and money when talking to a technician.