What does it mean?
C1705 is a Chassis (ABS, traction control, steering) fault code. It indicates: EPS ECU Precharge Circuit Fault .
Symptoms
- EPS warning lamp on with no assist, or assist arriving several seconds late after start-up
- Steering heavy immediately after start and normal once the engine has run for a while
- Assist dropping out during cranking or on cold mornings when battery voltage is lowest
- No or intermittent scan tool communication with the steering module
- Code sets straight at ignition on, before the vehicle is even driven
Likely causes
- Open or drifted precharge resistor inside the EPS ECU
- Capacitor bank aged and no longer holding charge
- Low battery voltage or high resistance on the main power feed so the capacitors never reach threshold
- Corroded, loose or heat-damaged main power connector or ground point
- Undersized, damaged or partially open fusible link feeding the unit
- Internal monitoring or driver circuit fault in the ECU
- Moisture or corrosion on the ECU board
How to fix it
- Test the battery and charging system; check state of charge and cranking voltage
- Voltage drop test the EPS main feed and ground with the assist loaded
- Inspect the power connector terminals for heat discolouration and spread contacts
- Monitor EPS supply voltage in live data with ignition on and with the engine running
- Check the fuse and fusible link for a partial break, not just visual continuity
- Repair any harness or ground fault found and retest before condemning the unit
- If the supply is proven good, the fault is internal: replace the EPS ECU and calibrate the steering angle sensor