Cruise Control Multi-Function Input B Circuit
The cruise control system has detected a problem with its secondary input switch or circuit, like a stuck button or broken wire preventing the system from receiving commands. The ECU can't tell if you're trying to adjust cruise speed because the signal isn't coming through properly.
The ECM monitors voltage levels from the cruise control multi-function switch (typically the set/accel/coast/resume buttons on the steering wheel or stalk). It expects specific voltage patterns when each button is pressed and checks for continuity in the circuit. If voltage readings fall outside expected ranges or the circuit shows intermittent signals, the fault is triggered.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Switch Circuit Voltage | 0.2V to 4.8V (varies by button pressed) | Open circuit (5V+) or short to ground (<0.1V) persistently |
| Signal Continuity | Stable voltage for duration of button press | Intermittent dropouts or no signal when button activated |
Code P0589 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0589 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.