A technician is diagnosing an intermittent loss of communication with the instrument cluster on a vehicle. A scan tool intermittently reports 'U0155 - Lost Communication with Instrument Panel Cluster (IPC) Control Module'. All other modules on the high-speed CAN bus are communicating normally. What is the most likely cause?
- AA short to ground on the CAN High wire.
- BA power supply issue to the IPC module.
- CAn open circuit in the CAN Low wire specifically to the IPC.
- DA faulty IPC module.
Show answer & explanationAnswer & explanation
Correct answer: C. An open circuit in the CAN Low wire specifically to the IPC.
If only the IPC is intermittently losing communication, and other modules on the same high-speed CAN bus are working, it points to an issue specific to the IPC's connection to the bus. An open circuit in either CAN High or CAN Low wire to a specific module can cause intermittent communication loss for that module, while the rest of the bus remains functional. A complete break would cause constant loss, but an intermittent open could cause the flickering communication.
Why the other options are wrong
- A. A short to ground on the CAN High wire would likely affect communication for ALL modules on that bus segment, not just the IPC.
- B. A power supply issue to the IPC would typically result in a complete and constant loss of communication and possibly a blank display, not intermittent communication with a 'U' code.
- D. A faulty IPC module is possible, but a wiring fault is often a precursor, and 'U' codes often point to communication issues which can be wiring related.
U0155 Intermittent (CAN Bus)
An intermittent U0155 DTC (Lost Communication with IPC) with other CAN modules working normally suggests an open circuit or poor connection in the CAN High or CAN Low wires specifically leading to the Instrument Panel Cluster module.
- CAN bus uses two wires (High & Low).
- Open in one wire to a module can cause intermittent comm loss.
- Other modules working rules out general bus fault.
Memory trick: U0155, just one module 'LOST': 'OPEN' wire, the 'SIGNAL' is 'CROSSED'.