The P0859 code in your 2020 Lincoln MKZ indicates the traction control input signal to the transmission is providing higher voltage than expected. This affects how the transmission responds to traction control system requests.
Understanding High TCS Signal
The MKZ's TCM expects specific voltage levels from the traction control system. High voltage typically indicates an open ground or short to power, causing the signal to rail high.
Common Causes of P0859
- Open circuit in signal ground
- Short to battery voltage
- TCS module output failure
- Disconnected wiring
- Connector damage
- CAN bus issues
Symptoms of High TCS Signal
- AdvanceTrac warning light
- Check engine light on
- Transmission may act as if slip is constant
- Reduced performance modes
- AWD system affected (if equipped)
- Erratic TCS behavior
Lincoln AdvanceTrac System
The MKZ uses Ford's AdvanceTrac system for stability and traction control. P0859 affects the communication between this system and the transmission, potentially causing incorrect responses.