We use cookies for basic analytics — nothing loads until you accept. You can decline and keep browsing normally. Privacy Policy
Diagnostic trouble code U01B4 indicates: Lost Communication With Brake System Control Module B. It was set by your vehicle's onboard diagnostics system and will typically keep the check engine light on until it's addressed.
Which ECUs store U01B4 is read from your file during analysis. DTC Removal is available on supported ECUs for these makes:
Upload your ECU file and DTC Doctor will detect this code (and any others) automatically, then remove it for good — no dealer visit, no guesswork.
Analyze My File Free →