Piston movement does not correlate to MPU motor speed (Motor Pump Unit)
1. Check oil level, and perform an air evacuation procedure. 2. Run the Diagnostic SelfTest (requires Parking Brake to be applied). - Diagnostic self test may isolate (pin-point) the root cause of problem, by setting other DTCs. 3. If neither OMV, nor DMV, trouble codes are set/stays active, check for hydraulic leackage on: - Hoses - CVU - MPU 4. Check operation of OperationalModeValve and DegradationModeValve, and thier related solenoids: - NormalModeSolenoid (V197) - CasterDegradationSolenoid (V199) - FixedDegradationSolenoid (V198) 5. Check if hudraulic pump rotates with electric motor (e.g. by measureing hydraulic pressure in M1 and M2). 6. Check CPS function by moving tag axle from side to side, while logging the cylinder psiton position in SDP3. If the fault only occurs at very low temperatures(-30C), 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 EST in released or fixed mode
Diagnostic depth
Piston movement does not correlate to MPU actual motor speed (Motor Pump Unit).
• Air in the hydraulic system • Extremely low temperature has caused the hydraulic oil to solidify - see DTC 0x0276 • Hydraulic leakage - oil level low - Hydraulic hose broken - loss of pressure - Hydraulic connector loose - loss of pressure - Cylinder piston rod seal is degraded - loss of pressure - MPU oil reservoir seal has failed - oil level low • OMV is broken (stuck in open position) • DMV is broken (stuck in open position) • Mechanical coupling between MPU electric motor and hydraulic pump is broken • MPU hydraulic pump is broken/degraded • CPS is faulty