What it means
Same as P0581 on input B. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
How it works
Input B is one of the cruise-control switch signals read by the control module to identify button commands. P0593 sets when the module sees the input B signal higher than expected, such as when the signal wire is shorted to supply voltage; cruise buttons may stop responding or work intermittently.
Common causes
Most likely first.
- Signal shorted to supply
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Cruise-control buttons may not respond
- Cruise control unavailable or intermittent
- Check-engine light
How to diagnose it
- Use a scan tool to confirm P0593 and review freeze-frame data and live cruise-switch input B status to see whether the signal remains high when no button is pressed.
- Inspect the cruise-control switches, input B wiring, and connectors for chafing, moisture, corrosion, pin push-back, or contact with a B+ wire.
- With the circuit diagram, check whether the input B signal is shorted to supply voltage and whether connector pin contact is sound.
- Wiggle the input B harness and connectors while monitoring the scan-tool signal to look for a change that reveals an intermittent fault.
- If wiring and connections check out, test the switch and input circuit against the manufacturer's specification, then consider a control-module fault.
Common fixes
- Repair chafed input B wiring or separate it from a pinched supply wire.
- Clean or replace corroded or damaged connector terminals and restore proper pin retention.
- Replace a faulty cruise-control switch assembly if its input B signal fails testing.
- Repair or replace the control module only after the input B circuit and switch test correctly.
Can I keep driving?
You can generally drive without cruise control if the throttle and brakes behave normally, but avoid relying on cruise until the fault is repaired. Stop using cruise if it behaves unpredictably.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.