How to Fix U0155 Code: Diagnosis & Repair Guide

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 IPc module image

If you're driving and suddenly your car's warning light illuminates, there's a good chance you're experiencing problems with the U0155 code. This indicates issues with the instrument clusters, and it needs to be fixed as soon as possible. 

In this blog post, we'll explain what the U0155 code is, what its causes and symptoms are, and how to fix it. Keep reading for more information!

What is Code U0155?

The U0155 is a diagnostic trouble code defined as "Lost Communication with the Instrument Panel Control (IPC) Module." So what does this mean? It indicates a communication loss within the Transmission Control Module (TCM). 

When the Powertrain Control Module (PCM) doesn't receive a signal from the instrument panel cluster or the IPC module doesn't receive a signal from the PCM, the CAN bus fault occurs.

This issue needs to be addressed because, without this Controller Area Network (CAN) bus, vital control modules won't exchange information with each other. When this happens, the code U0155 will be triggered.

Symptoms of Code U0155

Having a faulty CAN bus can cause various symptoms. One such symptom is the Malfunction Indicator Light (MIL) coming on. Apart from the illuminated check engine light, you may also experience these symptoms:

  • All indication light is on in the instrumental panel and instrument cluster.
  • No indicator lights in the instrumental panel and instrument cluster

Causes of Code U0155

Although the symptoms of this trouble code are not as many as the other codes, its causes are varied. Here are some of the common reasons:

  • Missing or loose CAN bus connection
  • Short to ground in the CAN_H or CAN_L circuit
  • Open circuit in the CAN_H or CAN_L circuit
  • Faulty control module

How to Diagnose Error Code U0155?

Before you start fixing this issue, it is crucial to thoroughly diagnose all the possible causes to fix the right problem. You will need an OBD scan tool that can read and clear trouble codes to do this. Let's get started!

Check for Other Diagnostic Fault Codes

In some cases, trouble codes detected by your OBD scanner are often accompanied by other fault codes. Make sure to check for any other error codes before trying to fix code U0155. Remember to write all these other codes before clearing them, as these may be helpful when you make a diagnosis.

If any of the codes gathered are associated with transit or Vehicle Identification Number (VIN), battery or ignition issues, or other vehicle-related problems, fix these first. If all other codes have been repaired but the U0155 trouble code remains, proceed to inspect for any grounded electrical wires.

Visual Inspection

  • Faulty grounds are a common source of failure and a good starting point, so check all the grounds on the vehicle. 
  • Check for bare wires, a loose connection, or a blown fuse. If you find an open circuit, fix it and clear the codes.
  • Check all connectors and make sure they are correctly connected.

Check Battery Voltage

Check the battery for proper voltage using a voltmeter. This ensures that the battery is not the cause of the problem. Replace the battery if it's the cause.

Clear Codes and Test

Once you have fixed the problem, clear the codes using a code reader or scanner. After clearing the codes, test drive the vehicle to see if it has fixed the issue. If not, then further diagnosis.

How to Fix Code U0155?

If you find any problems while diagnosing, fix them thoroughly until the code disappears. But, if you are unsure about the repair process, follow the steps below. But as we've always reminded you, only do it yourself if you are mechanically inclined.

Step-by-Step Guide to Fixing the Grounds for the IPC Module

The first fix you can try is cleaning the grounds for the IPC Module to perform it:

  1. Disconnect the negative battery cable.
  2. Remove the cover panel to access the IPC module ground screws.
  3. Remove the screws and gently pull out the IPC module from its connector.
  4. Clean the grounds with a wire brush until they are shiny.
  5. Repair or replace if cleaning the grounds does not work.
  6. Reinstall the IPC module making sure that all of the grounds are tight.
  7. Reconnect the negative battery cable.
  8. Start the ignition and check for proper operation.
  9. Clear any codes that may have been stored during the repair process.

Step-by-Step Guide to Fixing the IPC Module Connector

If you've followed these steps and are still having issues, you can try repairing the IPC module connector. To perform it:

  1. Disconnect the negative battery cable before beginning.
  2. Once located, check the connectors and wiring. Inspect if there are scraping, burned spots, and damaged wires.
  3. Pull the connectors apart and carefully inspect the terminals (the metal parts) inside the connectors.
  4. Check for a green hue or burned appearance. If terminals need to be cleaned, use an electrical contact cleaner and a plastic bristle brush. Allow drying before adding dielectric silicone grease to the terminal contact.
  5. Before connecting the connector to the IPC module, use a digital volt-ohm meter (DVOM). Make sure that your IPC module has power and ground connections.
  6. Reconnect the battery while the IPC is still disconnected
  7. Connect the red lead of the DVOM to battery positive (+) and the black lead to ground
  8. Start the ignition with your foot on the brake, and observe the voltage reading.
  9. If it's below 11 volts, there is a problem with your IPC module, and you will need to replace it.

Step-by-Step to Replacing the IPC Module

If you need to replace your IPC module, here is a quick guide on doing it.

  1. First, disconnect the battery.
  2. Then, remove the instrument panel cluster (IPC) by gently pulling it straight out.
  3. Next, disconnect the IPC connector from the IPC module.
  4. Now, remove the four screws that hold the IPC module in place.
  5. Finally, install the new IPC module, reconnect the connector, and then reattach the screws.

If all else fails, replacing or reflashing the PCM is your last resort. However, it is not a common fix for the U0155 code, so performing the fixes above will solve it.

Common Mistakes When Diagnosing the Code U1500

As mentioned above, the U1500 code is prone to misdiagnosis, primarily when other codes are associated. So, failure to scan for other codes is one of the common mistakes people make. Aside from it, here are some other common mistakes:

  • Failure to check the fuses
  • Failure to check for voltage drop
  • Incorrectly testing the PCM
  • Replacing parts without performing further diagnosis. For example, replacing the IPC is not the real cause of the problem.
  • Not checking for damaged wires and connectors

Keep in mind that these are just some of the common mistakes made when diagnosing a U1500 code. So, if you come across this code, make sure to avoid these mistakes to save time and money.

Code U1500 FAQs

1. Is this code U1500 serious?

A U0155 code is considered a significant problem and can generate severe issues with your vehicle. Suppose the other control modules lost communication with the (PCM) Powertrain Control Module. In that case, this will lead to the inability to keep track of essential control systems that enable your car to function properly.

2. How much does it cost to fix?

This will depend on your vehicle's make and model and the specific problem. However, most car owners report spending around $500 on parts and labor to fix this.

3. Can I prevent the issue from coming back?

If you want to avoid this issue in the future, make sure to keep up with your car's maintenance. By doing these things, you can help to prevent any problems with your car's control module.

4. What OBD scanner should I use to diagnose the issue correctly?

You can use any OBD scanner when diagnosing this error code; however, an advanced scanner will be able to give you a more accurate diagnosis.

5. If my car has this issue, can I still drive it?

Yes - you can continue to drive your car as usual until you have the issue fixed. Just be aware that if the U0155 error code is not fixed, it could cause problems with your car's performance.

Conclusion

The U0155 error code is serious and should be addressed as soon as possible. Although you can still drive despite having this issue, if left unfixed, this problem may lead to more severe issues in the long run.

We hope this guide helped clear the U0155 code. If you are not confident in doing this on your own, we urge you to seek the help of a professional mechanic. If you have questions, please don’t hesitate to reach out for assistance. Thank you for reading.