The reference voltage is faulty (REFERENCE_VOLTAGE_ERROR)
As long as no degenerated functionality is observed, no action needs to be taken. If there is a suspicion that this DTC causes deteriorated function, try to exchange the ECU (only if the DTC is active!). Do a spare parts programming and observe the systems functionality. The reference voltage unit is integrated in the ACS and cannot be exchanged separately.
What you'll see
No driver-visible symptom recorded.
System reaction
The voltage that the ECU assumes may differ from the real voltage. The analogue sensors connected to the ACS may be affected by this error by means of erroneous values. The functionality is, however, normally not affected.
Diagnostic depth
The DTC becomes active if the physical reference voltage is improbably high or low for 1 second. The DTC becomes inactive if the reference voltage is in-between permitted limits for at least 1 second. Observe that the physical reference is converted to a virtual reference that can be read out from the ACS ECU.
Faulty reference voltage unit.