Automobile & Light Truck Certification Test A5 BrakesPower Assist Unit Diagnosis and RepairMedium
A technician is diagnosing a vehicle with an electric power steering (EPS) system that has a 'stiff' or 'heavy' steering feel, but no warning lights are illuminated on the dash. A scan tool reveals no Diagnostic Trouble Codes (DTCs). Which of the following should the technician investigate FIRST?
- ATire pressures and front-end alignment.
- BLow power steering fluid level.
- CA seized steering rack.
- DA faulty EPS control module.
Show answer & explanationAnswer & explanation
Correct answer: A. Tire pressures and front-end alignment.
Before delving into complex electrical system diagnostics, it's crucial to rule out basic mechanical issues that can cause heavy steering. Incorrect tire pressures (especially low) or poor front-end alignment (like excessive caster or toe-in) significantly increase steering effort and are common culprits for a 'stiff' feel, even with a functioning EPS system.
Why the other options are wrong
- B. EPS systems are electric, not hydraulic, so there is no power steering fluid to check.
- C. A seized steering rack would likely cause an extremely hard or locked steering, often with grinding noises, and might trigger a DTC if the EPS motor tries to compensate. 'Stiff' is a milder symptom.
- D. A faulty EPS control module would typically trigger a DTC, and the question states no DTCs are present.
EPS Heavy Steering Diagnosis
Initial diagnostic steps for heavy steering in an Electric Power Steering system, starting with basic mechanical checks before electrical diagnostics.
- Rule out non-EPS issues first.
- Check tire pressure and alignment.
- No fluid in EPS systems.
Memory trick: Heavy steering, no lights? Check tires and alignment, make it right!