The P0858 code in your 2023 Cadillac CT4 indicates the traction control input signal to the transmission control module is providing lower voltage than expected. This affects the integration between traction control and transmission operation.
Understanding Low TCS Signal
The CT4's transmission uses traction control data to optimize shift strategy during slip events. Low voltage in this circuit suggests signal degradation that may prevent proper TCM response to wheel slip.
Common Causes of P0858
- Short to ground in TCS signal circuit
- High resistance in wiring
- TCS module output failure
- CAN bus communication issues
- Connector corrosion
- Ground connection problems
Symptoms of Low TCS Signal
- StabiliTrak warning light
- Check engine light on
- Reduced traction control response
- Transmission may not adapt to slip
- V-mode (if equipped) affected
- Performance limitations
CT4 Performance Modes
The CT4 includes performance driving modes that coordinate transmission and traction control. P0858 may limit the effectiveness of these modes, particularly in Sport or Track modes.