Electronic Struts: How They Work and How to Identify Them

What Electronic Struts Are

An electronic strut is a structural suspension strut with an electronically adjustable damper built in. Like a conventional strut, it locates the wheel, supports the coil or air spring and carries loads into the body at its upper and lower mounting points. The difference is inside the damper. A conventional damper has fixed valving that always reacts the same way. An electronic damper has an actuator that a suspension control module commands to make damping softer or firmer. Manufacturers market the feature under names such as adaptive suspension, continuous damping control, magnetic ride control or dynamic chassis control. Some vehicles use electronic struts at the front with electronic shock absorbers at the rear.

The quickest way to identify one is to look for an electrical connection. If a wiring harness plugs into the strut itself, usually at the top near the upper mount or on the body of the damper, the strut is almost certainly electronically controlled. Most vehicles with this feature also have a driver-selectable mode such as Comfort, Normal or Sport that changes how the suspension feels. Some systems adjust automatically and have no switch.

How Electronic Struts Work

A damper controls spring motion by forcing hydraulic fluid through small passages as the piston moves. In a conventional strut, the size of those passages and the valve stacks are set at the factory. In an electronic strut, the restriction can change. The most common design uses a solenoid-operated valve, located either inside the piston rod or in an external canister on the strut body. When the control module varies the current to the solenoid, the valve opens or restricts the flow path. Depending on the design, this gives softer or firmer damping in small steps or across a continuous range.

Magnetorheological designs work differently. The damper is filled with a fluid that contains fine iron particles, and an electromagnetic coil in the piston creates a magnetic field. More current makes the fluid more resistant to flow, so damping firms up without any moving valve parts. Both designs rely on the same kind of inputs. The control module reads wheel speed, steering angle, braking, body accelerometers and, on many vehicles, ride height sensors at each corner. It adjusts each damper independently, many times per second. The goals are to reduce body roll in corners, limit nose dive under braking and keep the tires in contact with rough pavement.

When the system detects a fault, it normally stores a diagnostic trouble code, shows a warning and switches the affected damper or the whole system to a fixed fallback mode. Depending on the design, that fallback can feel noticeably harsher or softer than normal. That change in ride is often the first clue owners notice.

Designs and Conditions That Change the Answer

The biggest variable is whether the strut also contains an air spring. On vehicles with air suspension, the front assembly is often an air strut: an electronic damper surrounded by a rubber air bag, with both an air line and an electrical connector at the top. That system controls ride height as well as damping. Because the spring is pressurized, it must be handled with the manufacturer's procedure. On vehicles with coil springs, the electronic damper only controls motion and does not change ride height. Separating the spring from the strut requires a proper spring compressor, just as with a conventional unit.

Model, trim and options also matter. The same vehicle line may have conventional struts on base trims and electronic struts on upper trims or with a specific suspension package, so the make and model alone are not enough. Mid-cycle updates can change the damper design or its connector. Some vehicles have electronic dampers on only one axle.

Not every wire near a strut belongs to it. Wheel speed sensor and brake pad wear sensor wires often run along or clip to the strut body on their way to the knuckle or caliper. A small sensor with a linkage arm to a control arm may serve headlamp leveling rather than adaptive damping. Follow each wire to where it ends before drawing conclusions.

How to Identify Electronic Struts and What to Check

Start with the paperwork and the controls. The owner's manual, original window sticker or build sheet will list adaptive or electronically controlled suspension if it was fitted, and a dealer parts department can usually confirm factory equipment from the VIN. Inside the car, look for a suspension or drive mode selector, and note whether the instrument cluster has ever shown suspension-related messages. Then inspect the hardware with the vehicle parked on level ground. Open the hood and look at the top of each front strut tower. Check the rear shock or strut tops as well, which may be reached from the trunk, the cargo area or underneath. An electrical connector plugged into the top or body of the strut confirms an electronic unit, as does a short harness running from the strut to the vehicle body.

If you suspect a problem, look for oily residue on the damper body, damaged or corroded connectors, chafed wiring and loose or cracked upper mounts. On air strut systems, also check for torn air springs. Listen for clunks over bumps, and note whether one corner rides harder than the others. A clunk does not always come from the strut. Worn ball joints, tie rod ends and sway bar links make similar noises, so check for joint play before blaming the damper. Reading the suspension module's trouble codes requires a scan tool that can access chassis modules. Many basic code readers only show engine and emissions data.

Match any replacement to the vehicle's original configuration. An electronic strut will not plug into a car built for conventional ones. A conventional strut fitted to an electronic system will usually trigger a fault unless the manufacturer or supplier provides a supported conversion. Replace dampers in axle pairs unless the service information says otherwise. If you do the work yourself, raise the vehicle only at the specified lift points and set it on rated jack stands before working underneath. On air suspension, follow the service mode or depressurizing procedure first. Tighten every fastener to the specification in the service information, and replace any bolts designated for single use. Many systems require a calibration or initialization with a scan tool afterward. A wheel alignment check is commonly needed after strut replacement, particularly at the front.

Limitations and When to Get Professional Help

This article describes common designs, but connector locations, fallback behavior and replacement steps vary by manufacturer and model. Fastener torque values, ride height targets and wheel alignment settings must come from the factory service information for your specific vehicle, not from general guides. A warning message does not tell you how serious the fault is or how far the car can safely be driven. A suspension warning combined with unusual handling, noise or a sagging corner is a reason to have the vehicle checked promptly.

Get professional help if you lack a scan tool that can read and calibrate the suspension module, if the vehicle has air suspension, or if the fault persists after you have checked the connectors and wiring. A shop with the correct diagnostic software can tell whether the strut, a sensor, the wiring or the control module is at fault. That diagnosis keeps you from replacing an expensive damper that was never the problem.