ASE A4 Suspension and SteeringSuspension System Diagnosis and RepairHard
A vehicle with an active suspension system featuring continuously variable dampers exhibits a persistent harsh ride quality and occasional 'thumping' noises over road imperfections. A scan tool reveals no diagnostic trouble codes (DTCs) related to the suspension system, but live data shows all damper control valves are commanded to a 'firm' setting even on smooth roads. Which of the following is the MOST likely cause?
- AStuck open damper control valve
- BShort circuit in a damper solenoid
- CFailed ride height sensor
- DMalfunctioning accelerometer/G-sensor
Show answer & explanationAnswer & explanation
Correct answer: D. Malfunctioning accelerometer/G-sensor
Continuously variable dampers rely on input from various sensors, including accelerometers (G-sensors), to determine road conditions and vehicle dynamics. If an accelerometer is malfunctioning, it might incorrectly report constant high G-forces or extreme road conditions, causing the control module to continuously command a 'firm' damper setting, resulting in a harsh ride and thumping noises.
Why the other options are wrong
- A. A stuck open damper control valve would likely result in a soft, bouncy ride, as it would not be able to firm up the damping, contradicting the 'firm' setting data.
- B. A short circuit in a damper solenoid would usually result in a DTC, and depending on the failure mode, might cause a very soft or very firm setting for that specific damper, but less likely all dampers commanded firm without a DTC.
- C. A failed ride height sensor would primarily affect ride height control or cause an uneven stance, not typically a persistent harsh ride with 'firm' damper commands.
Active Suspension Sensor Inputs
Active suspension systems use various sensors, including accelerometers, to monitor vehicle dynamics and road conditions, informing damper control.
- Accelerometers measure vertical and lateral G-forces.
- Ride height sensors monitor vehicle level.
- Steering angle sensors and wheel speed sensors provide additional data.
Memory trick: Harsh ride, firm command, check the sensor, understand the land.