Cruise Control Multi-Function Input B Circuit Stuck
The cruise control button circuit is stuck sending the same signal to the engine computer, like a doorbell that won't stop ringing. The ECU can't tell when you're actually pressing or releasing the cruise control buttons.
The ECU monitors the voltage signal from the cruise control multi-function input B circuit, expecting it to change states when buttons are pressed. If the signal remains constant or stuck at one voltage level without transitioning, the ECU logs this fault. The circuit should toggle between high and low states corresponding to button presses.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Input B Signal Voltage | 0-5V with state transitions on button press | Signal stuck at constant voltage with no transitions for extended period |
| Signal Response Time | State change within 500ms of button activation | No state change detected or delayed beyond timeout threshold |
Code P0590 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, P0590 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.