DTC U2004: Transmitted SPI Data Output Low: Description
DTC U2004 indicates Body Function Controller (BFC) has detected a short to ground or open on Serial Peripheral Interface (SPI) data line from Instrument Panel Cluster (IPC) to BFC. DTC U2004 will set when ignition 0 input is active, and serial data line from IPC to BFC is open or shorted to ground for longer than 5 seconds.
When DTC U2004 is set, THEFT SYSTEM, ABS, and SERVICE VEHICLE SOON indicators will illuminate, fuel and temperature gauges will read zero, and PRNDL indicator will be blank. DTC U2004 can be cleared using scan tool, or history DTC will disappear after 100 ignition cycles if fault conditions do not reoccur.