A technician is diagnosing a vehicle with an electric power steering (EPS) system that has a 'hard steering' complaint, but no diagnostic trouble codes (DTCs) are present. The technician observes that the steering effort is consistently high at all speeds. Which of the following is the MOST likely cause?
- AA faulty steering angle sensor providing incorrect input to the EPS module.
- BA mechanical binding in the steering column or rack assembly.
- CA low battery voltage causing reduced EPS motor output.
- DA intermittent open circuit in the EPS motor power supply.
Show answer & explanationAnswer & explanation
Correct answer: B. A mechanical binding in the steering column or rack assembly.
If an EPS system has a consistently hard steering complaint without DTCs, it strongly suggests a mechanical issue rather than an electrical or electronic one. Mechanical binding in the steering column, universal joints, or the rack assembly itself would cause consistently high steering effort regardless of speed and would not typically trigger a DTC unless it directly affected an electrical sensor reading outside its range.
Why the other options are wrong
- A. A faulty steering angle sensor would likely cause inconsistent assist, improper centering, or trigger a DTC if its readings were implausible.
- C. Low battery voltage would affect many systems and might cause intermittent or reduced assist, potentially with DTCs, but consistent hard steering at all speeds without codes is less likely.
- D. An intermittent open circuit would cause intermittent loss of assist, not consistently hard steering, and would likely set a DTC when the circuit opens.
EPS Hard Steering (No DTCs)
When an Electric Power Steering system exhibits consistently hard steering without diagnostic trouble codes, the problem is often mechanical binding within the steering column or rack assembly, as the EPS system is functioning but cannot overcome the physical resistance.
- No DTCs suggests non-electrical issue.
- Consistent hard steering points to mechanical drag.
- Inspect steering column U-joints, rack, and bearings.
Memory trick: No codes, so it's not the brain; it's the muscle binding.