P0578

Code

LAND ROVER P — Powertrain

Multifunctional Speed Control Input A circuit is stuck

Brand: LAND ROVER

Type: P — Powertrain

Views: UK: 15 EN: 25 RU: 18

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Short to battery voltage or to ground in the input wiring
Open or shorted wire/poor continuity in the harness to the multifunction speed-control switch or sensor
Corroded, bent, or pushed-back connector pins at the switch or module
Failed or mechanically stuck multifunction speed-control switch / sensor (steering wheel/column switch assembly)
Water intrusion or contamination in connector or switch
Module input driver fault (PCM/BCM/steering module) or software anomaly

Symptoms

Cruise control will not engage or is inoperative
Cruise-related warning light or message on the dash
Cruise on/off or set/resume buttons unresponsive
Intermittent or inconsistent cruise behavior
Related vehicle speed/driver-assist features degraded or disabled

What to check

Read and record freeze frame and all related DTCs using a capable scan tool (check other modules: BCM, ABS, instrument cluster).
Monitor live data for the 'Multifunction Speed Control Input A' while operating the steering-wheel switches — look for expected state changes.
Visually inspect wiring and connectors at the steering column, multifunction switch, and the control module for corrosion, damage, water, or loose pins.
Backprobe the input pin at the switch and at the module while operating the switch to confirm signal behavior.
Measure battery voltage and ground reference at the connector to ensure proper supply and ground.
Perform a wiggle test on the harness while observing live data to locate an intermittent fault.

Signal parameters

Expected digital switch signal: toggles between LOW (≈0–0.5 V) and HIGH (≈4.5–5 V or battery voltage via pull-up) when the switch is operated.
If the circuit is a pulse/vehicle speed type, expect frequency proportional to road speed (pulses/sec) rather than a fixed voltage.
Stuck condition: signal remains constant (no change) or is clamped to ~0 V (short to ground) or ~battery voltage (short to Vb).
Module input should not show constant high/low when switch is actuated — confirm change on live data during operation.

Diagnostic algorithm

Connect a diagnostic scan tool and confirm P0578 is present; record freeze frame and any other DTCs.
With ignition ON, monitor the multifunction speed control input A parameter while an assistant operates the steering-column/switch buttons. Verify whether the signal changes.
If the signal does not change, perform a visual and physical inspection of the steering-column switch and connector for damage, corrosion, or water entry.
Backprobe the switch connector and measure voltage at the input pin while operating the switch. Compare to expected LOW/HIGH values. Note if the signal is stuck high or low.
If the input is stuck, isolate the circuit: disconnect the switch and measure for short to ground or battery on the harness side. Use an ohmmeter to check continuity to ground and to battery (with battery removed where required).
Wiggle the harness and connectors while monitoring the input to detect intermittent faults. Inspect harness routing for chafing points or pinches.
If wiring and connectors check good and the harness side changes properly when the switch is operated, suspect the switch assembly and replace or bench-test the switch where possible.
If the switch is good but the module input remains incorrect, check for proper reference voltage and grounds at the module. Consider reprogramming/update or module replacement only after all wiring/switch checks pass.
After repair, clear DTCs and perform a test drive/operation cycle to confirm the code does not return and related functions operate normally.

Likely causes

Failed/malfunctioning multifunction speed control switch (steering column)
Short to ground or constant 12V on the input circuit (stuck high/low)
Loose or corroded connector/pin at the switch or control module
Damaged wiring harness (chafing, pinched near steering column or under dash)

Fault status

⚠️ Status

Multifunctional Speed Control Input A circuit stuck (signal constant or out of expected range) — inspect switch, wiring, and module inputs.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours