Instrument Cluster Error Codes Explained
Instrument clusters used to be very simple. Not much functioned without a direct connection to another part. Mechanical cables operated the speedometer, tachometer, and odometer gauges. Warning lights were directly wired to the engine computer, and the fuel gauge worked by resistance from the sending unit in the fuel tank. If something stopped working, it was usually an individual cable, electrical wire, or light bulb.
These days, an instrument cluster functions as a complex control module whose functions are integrated with many other systems. It uses data and signals transmitted from other modules to display information and operate all of the gauges. The cluster also works as an input device. A multi-function display controlled by buttons allows you to access data and settings in other control modules. When a setting is changed, the instrument cluster sends this data to the appropriate control module. Learn more here about all the things that can control the instrument cluster.
Since modern instrument clusters are integrated systems, it's not surprising to find that there are several common diagnostic trouble codes (DTC) that relate to their function. In this post, we're going to explore one of the most common ones: DTC U0155.
The Controller Area Network (CAN)
To fully understand instrument cluster error codes, you'll need to know what a vehicles Controller Area Network (CAN) is. The CAN bus is like the nervous system of the vehicle ('bus' refers to the physical wires that the CAN system uses.) Each control module on the network acts as a node to relay data between one another. This avoids complex wiring by allowing multiple sensor or actuator signals to travel across just two wires, known as CAN High and CAN low. Depending on the vehicle’s number of modules, there may also be CAN subnets between fewer control modules.
The instrument cluster on modern cars is an integrated part of the CAN bus. The cluster is the central hub for all necessary information to be displayed to the driver. For example, safety sensors may signal the brakes to apply or signal the engine to reduce speed. Simultaneously, the brake controller will send data to the instrument cluster to turn on indicator lights or display a message. This alerts the driver to know what is happening if a safety system intervenes. The instrument cluster’s gauges, indicators, and displays receive most data signals over the CAN to function. Some components may still be directly wired to the cluster.
A common CAN fault can cause loss of communication across several controllers, including the instrument cluster. As such, DTC U0155 is often related to CAN bus and/or (consequentially) instrument cluster errors. Keep in mind that CAN issues may or may not be isolated only to the cluster.
The On-Board Diagnostics (OBD)
As a control module, the instrument cluster also monitors itself for malfunctions and will set a diagnostic trouble code (DTC) to indicate the fault when a problem is encountered. A single controller within the cluster can lose communication with other control modules. When this happens, a unique DTC sets in each other module to indicate that it can’t 'talk' to this module. When communication is lost with the instrument cluster, the DTC U0155: “Lost Communication with Instrument Panel Control (IPC) Module” will be set in other controllers. This code may set for several reasons, including:
- Loss of power to the IPC
- Loss of ground to the IPC
- Loss of CAN signal to the IPC
- Internal failure of the IPC
Symptoms of a U0155 DTC may include a complete or partial loss of instrument cluster functions. If the instrument cluster still has power, there may be one or more other DTCs stored, indicating a primary fault. This means that U0155 could be a symptom of another fault. For example, an internal hardware DTC may prevent CAN communication.
Why Choose ISS?
Instrument cluster repair codes can be tricky but can usually be tracked down with a bit of trial and error. If you have made a diagnosis and determined your instrument cluster is faulty, you can send it to ISS for repair or replacement.
ISS Automotive is one of the most reliable names in the automotive and truck industry, since 1949. We provide quality replacement parts and repairs for popular car and truck clusters. When you shop with us you get:
- Correct fitment. Your parts will be built to OEM standards and programmed to work with your exact model year.
- Easy installation. All you need are basic hand tools to remove your old gauges and install the new ones from ISS.
- Customized upgrades. ISS offers LED lighting upgrades along with other customization options that vary by part.
- Limited lifetime warranty. This includes all our new or remanufactured products, replacement/exchange units, and repair units.
- Free and fast shipping in the continental USA.
Have questions about cluster repair codes or need help finding the right part? Please contact us!