Fail-Safe/Protection Back-up Modes
The Infiniti Q50 Direct Adaptive Steering (DAST) is a steer-by-wire system using three control units, switches, sensors and actuators to control the steering gear assembly.
NOTE: Sensors in the steering angle actuators measure the steering resistance (reaction force). That information is used to adjust the steering force actuator, giving the driver an accurate steering feel of the road conditions.
The DAST system also includes a steering clutch on the steering column.
- With the ignition OFF, the steering clutch is engaged, giving direct mechanical connection of the steering wheel to the steering gear.
- With the engine ON or Ready ON in normal driving situations, the steering clutch is disengaged, allowing the DAST system to control the steering gear (drive-by-wire).
If one of the three control units detects a system fault condition, a fail-safe or a protection function back-up is activated. Since the three control units monitor malfunctions mutually, the DTC codes vary from control unit to control unit.
If a DAST system fault occurs, the back-up clutch mechanically locks the steering column shaft to the steering shaft. This provides a direct mechanical linkage between the steering wheel and the tires.
Whether a fail-safe or protection back-up function is activated depends on the detected fault condition or DTC. Refer to DIRECT ADAPTIVE STEERING Fail-Safe and DIRECT ADAPTIVE STEERING-Protection Function in the STC section of the Service Manual for a list of DTCs and details on fail-safe mode and protection back-up function.
For fail-safe mode 1, 2 or 3, the power steering warning lamp illuminates and the Warning Chassis Control System Error will illuminate the Information Display screen, when driving the vehicle, and remain on until the IGN is cycled OFF. The steering wheel turning effort is increased. Greater steering wheel effort will be needed to steer the vehicle especially in sharp turns and at low speeds because the power steering assist has been reduced.
When the vehicle is in protection function mode, the power steering warning lamp illuminates, but the Warning Chassis Control System Error warning indicator light, in most cases, WILL NOT BE turned on because a protection back-up function condition does not indicate a malfunction. It is a temporary condition that will, in most cases, return to normal operation automatically once the cause has cleared. In protection function mode, the power steering assist may be reduced to protect the system from damage.
- The temperature of the DAS Control unit (steering angle actuator) is over heated (above 185F (85C) at ignition ON or becomes higher than the fail-safe threshold of 185F (85C) while driving.
- Steering wheel is operated repeatedly or continuously while parked or driving at a very low speed, causing over-heating at the steering angle actuators.
- When a front tire pushes against a curb or an obstruction continuously while attempting to turn the vehicle.
- When the engine is stalled.
- When the battery voltage is low (below 8 volts): Long-term storage condition, battery in poor condition or electrical draw with the engine OFF.
NOTE: For a low battery voltage condition – refer to ITB13-033 – “2014 Q50 Power Steering Warning Light ON with C13EB, C13E9 due to Low Battery Voltage”.
Driving while the DAST is in a fail-safe mode or a protection function mode, or driving after the DAST was in one of these modes, the following steering conditions may be experienced:
- Steering effort is higher than normal.
- While driving straight, the steering wheel may be off-center.
- While driving straight, if you relax your grip on the steering wheel, the steering wheel may not return to center under some circumstances.
- There may be some ratcheting feel when turning the steering wheel.
- Steering response is slow.
After a protective function condition has cleared or a fail-safe mode condition has been resolved, train (re-calibrate) the DAST system to return it to normal operation by performing these steps:
DAST Re-calibration
1. Safely drive to the side of the road and stop the vehicle.
2. Turn the ignition OFF and then ON (restart the engine/ready to drive mode).
3. While stopped:
a. Place the steering wheel in the straight ahead position (center position).
b. Turn the steering wheel left about 90 degrees from center.
c. Turn the steering wheel right about 90 degrees from center.
d. Repeat steps b and c one time.
4. Safely drive the vehicle onto the road and then drive as follows:
• In a straight line (hold the steering wheel so the vehicle stays in a straight line)
• On a smooth, straight, flat road
• Speed of 20 MPH or more (It is recommended that you stay below 40 MPH)
• For at least 5 seconds:
– The DAST will automatically correct the off-center condition.
– During the above drive, the steering will gently and very slowly move to a center position while driving straight.
NOTE:
- Make sure to operate the vehicle safely.
- Using a smooth, straight, flat road with very light or no traffic is recommended.
- Bumps, pot holes or other steering input may affect the calibration, which will require a repeat of steps 1 – 4.
- Traffic conditions that require steering input may affect the calibration, which will require a repeat of steps 1 – 4.
5. Recheck: If the steering wheel is still off-center while driving straight, repeat steps 1 – 4.
