Symptom
Steering feels heavy or inconsistent
The steering has become harder work than usual, or the effort changes when it should not.
On a car with variable-effort steering, over-light at speed is as much a symptom as heavy at parking speed. The system deliberately gives more assistance when manoeuvring and less at speed, because a very light wheel at motorway speed makes the car twitchy and tiring. A fault at either end of that range is the same fault.
A common and surprising cause is not the steering at all. The assistance level is set from road speed, so a wheel speed sensor fault or a lost speed signal makes the steering behave oddly while the steering system is perfect. Check for chassis codes before suspecting the rack.
On electric power steering, heavy steering is often the system protecting itself. Sustained use — repeated full-lock manoeuvring, or a long period of parking — heats the motor, and the controller reduces assistance until it cools. That is designed behaviour and it returns to normal. Low battery voltage produces the same reduction.
Rule out the free explanations first: tyre pressures, and whether it is heavy only at low speed or at all speeds.
Also described as: heavy steering, stiff steering, steering hard to turn, power steering not working, steering effort changed, steering feels light, فرمان یکنواخت نیست, فرمان گاهی سنگین میشود, direccion inconsistente, direccion asistida falla, volante pesado a veces, المقود غير متزن, الباور يفصل ويرجع, الدركسيون يثقل أحيانا
What this usually means
Inconsistency is the diagnostic content here, and it separates this from steering that is simply heavy. Assistance that varies — heavy then normal, or heavier in one direction than the other — is reporting something intermittent, and that points at different causes from a steady loss.
On an electric system, assistance that comes and goes is usually supply or thermal. The motor draws heavily at full lock and low speed, so a marginal battery, a poor earth or a failing alternator produces assistance that fades exactly when it is needed most. And several systems reduce assistance deliberately when the motor is hot after repeated full-lock manoeuvres — which is the system protecting itself rather than failing, and it recovers after a few minutes.
A steering angle sensor that has lost its reference produces inconsistency rather than absence. The module uses steering angle to decide how much help to give, so a reference lost by a battery disconnection, a column or rack repair, or an alignment leaves the assistance calibrated to the wrong centre. That is a calibration rather than a part, and it is the cheapest outcome on this page.
On a hydraulic system, inconsistency points at aeration or a failing pump. Air in the fluid compresses, so assistance varies with how much air is where — and the fluid's appearance says so immediately.
Mechanical inconsistency feels different and is worth separating. A tight spot at one point in the travel, or notchiness, points at a seized joint, a strut mounting or the rack itself — and it is felt with the engine off as well as on, which assistance faults are not.
Steering that changes without warning is more urgent than steering that is consistently heavy, because the driver is not braced for it.
Working through it
| What you find | Likely cause | How to confirm it | What fixes it |
|---|---|---|---|
| Assistance fades after repeated full-lock manoeuvres, returns after a few minutes | Thermal protection — the motor reducing output to protect itself, which is designed behaviour | Note the correlation with heavy low-speed use and the recovery on cooling. | No repair. If it happens on ordinary use, investigate the supply, which makes the motor work harder. |
| Assistance comes and goes with other electrical oddities | Supply — a marginal battery, a poor earth, or a failing alternator | Test battery and charging, and voltage-drop the earths under load. Read codes but do not act individually yet. | Repair the supply first. A steering complaint inside a group of faults is rarely the steering. |
| Heavier in one direction than the other | A steering angle reference lost, or a hydraulic valve wearing asymmetrically | Read live steering angle with the wheels straight; a non-zero value names the calibration. | Run the calibration. If the asymmetry persists on a hydraulic system, the rack's valve is worn. |
| Hydraulic system, fluid frothy or milky | Air in the fluid compressing — assistance varies with where the air is | Look at the fluid's appearance rather than only its level. | Repair the suction-side leak, refill and bleed lock to lock. |
| Tight spot at one point in the travel, felt with the engine off too | Mechanical — a seized joint, strut mounting, or the rack itself | Turn lock to lock with the wheels raised and the engine off. Assistance faults disappear with the engine off; mechanical ones do not. | Renew the seized component and align afterwards. |
| Inconsistency dates from a battery change or steering work | A calibration lost rather than a component failed | Ask what was done. This is the cheapest outcome and the most commonly missed. | Run the manufacturer's steering angle calibration. No part is required. |
-
Assistance fades after repeated full-lock manoeuvres, returns after a few minutes
- Likely cause
- Thermal protection — the motor reducing output to protect itself, which is designed behaviour
- How to confirm it
- Note the correlation with heavy low-speed use and the recovery on cooling.
- What fixes it
- No repair. If it happens on ordinary use, investigate the supply, which makes the motor work harder.
-
Assistance comes and goes with other electrical oddities
- Likely cause
- Supply — a marginal battery, a poor earth, or a failing alternator
- How to confirm it
- Test battery and charging, and voltage-drop the earths under load. Read codes but do not act individually yet.
- What fixes it
- Repair the supply first. A steering complaint inside a group of faults is rarely the steering.
-
Heavier in one direction than the other
- Likely cause
- A steering angle reference lost, or a hydraulic valve wearing asymmetrically
- How to confirm it
- Read live steering angle with the wheels straight; a non-zero value names the calibration.
- What fixes it
- Run the calibration. If the asymmetry persists on a hydraulic system, the rack's valve is worn.
-
Hydraulic system, fluid frothy or milky
- Likely cause
- Air in the fluid compressing — assistance varies with where the air is
- How to confirm it
- Look at the fluid's appearance rather than only its level.
- What fixes it
- Repair the suction-side leak, refill and bleed lock to lock.
-
Tight spot at one point in the travel, felt with the engine off too
- Likely cause
- Mechanical — a seized joint, strut mounting, or the rack itself
- How to confirm it
- Turn lock to lock with the wheels raised and the engine off. Assistance faults disappear with the engine off; mechanical ones do not.
- What fixes it
- Renew the seized component and align afterwards.
-
Inconsistency dates from a battery change or steering work
- Likely cause
- A calibration lost rather than a component failed
- How to confirm it
- Ask what was done. This is the cheapest outcome and the most commonly missed.
- What fixes it
- Run the manufacturer's steering angle calibration. No part is required.
Codes that produce this symptom (17)
Listed with the codes that most typically present this way first — the likeliest place to start.
- C0079 Variable Effort Steering Typical of this code Low
- P0550 Power Steering Pressure Sensor/Switch Circuit Typical of this code Low
- P0551 Power Steering Pressure Sensor/Switch Circuit Range/Performance Typical of this code Low
- P0552 Power Steering Pressure Sensor/Switch Circuit Low Typical of this code Low
- P0553 Power Steering Pressure Sensor/Switch Circuit High Typical of this code Low
- P0554 Power Steering Pressure Sensor/Switch Circuit Intermittent Typical of this code Low
- P0635 Power Steering Control Circuit Typical of this code Moderate
- P0636 Power Steering Control Circuit Low Typical of this code Moderate
- P0637 Power Steering Control Circuit High Typical of this code Moderate
- U0130 Lost Communication With Steering Effort Control Module Typical of this code High
- U0131 Lost Communication With Power Steering Control Module A Typical of this code High
- U0134 Lost Communication With Power Steering Control Module — Rear Typical of this code High
- U0319 Software Incompatibility With Steering Effort Control Module Typical of this code Moderate
- U0320 Software Incompatibility With Power Steering Control Module Typical of this code Moderate
- U0419 Invalid Data Received From Steering Effort Control Module Typical of this code High
- U0420 Invalid Data Received From Power Steering Control Module A Typical of this code High
- U0435 Invalid Data Received From Power Steering Control Module — Rear Typical of this code High
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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