DTC U0100, DTC U0121 Or DTC U0155

WARNING: This page is about a different car, the 2003 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

Code Definition

DTC U0100: Communication Error To Power Control Module (PCM)
DTC U0121: Communication Error To Anti-Lock Brake System/Traction Control System Hydraulic Unit/Control Module (ABS/TCS HU/CM)
DTC U0155: Communication Error To Instrument Cluster

Refer to PROCEDURES FOR DETERMINING LOCATION OF A MALFUNCTION under SYSTEM TESTS.