Degradation mode valve (DMV) is stuck, or Valve Position Sensor (VPS) is faulty
This DTC is just a pre-check that something migh be wrong with DMV or VPS. If we have a real issue DTC 628 (DMV error) or DTC 629 (VPS error) willl be set after Diagnostic Self test. If none of these extra fault codes and the ESTA system seems to work fine then you can disregard from an inactive DTC 598. If the fault only occurs at very low temperatures, the oil might have to be replaced. See service litterature for recommended oil quality in cold climate.
What you'll see
No driver-visible symptom recorded.
System reaction
Red Steer tag axle fault warn ESTA in normal operation mode
Diagnostic depth
The VPS is reporting a position of the DegradationModeValve (DMV) that does not correlate to the estimated locked state from the ECU.
This could be caused by three possible types of faults - electrical, mechanical, or temporary environmental disturbances. • Possible electrical faults: - Open circuit, or short circuit, in VPS (T1002) cable harness - Defect connector on VPS (T1002) cable harness - Defect connector housing on VPS (T1002) - Defect connector on ESTA ECU (E1003) cable harness - Defect sensor VPS (T1002) - Defect solenoid CDS (V1002) - Defect solenoid DLS (V1001) • Possible mechanical faults: - DMV mechanically stuck • Possible temporary environmental disturbances: - Extremely low temperatures will cause oil to solidify, thus jamming the valve - Exposure to extensive electro-magnetic radiation might disturb the sensor function