Cruise Control Multi-Function Input "B" Circuit High
P0593 indicates the cruise control multifunction input circuit B is reading a voltage level higher than the expected range. This typically affects the cruise control system's ability to receive input commands from the steering wheel controls or cruise control stalk.
What You Might Notice
- Cruise control inoperative or won't engage
- Cruise control light illuminated on dashboard
- Unable to set or maintain desired cruise speed
- Abnormal vehicle speed fluctuations when cruise control is active
- Cruise control switches unresponsive to commands
Most Common Causes
- 1
Faulty cruise control switch or stalk
The multifunction switch on the steering wheel or cruise control stalk may be malfunctioning, causing an excessively high voltage signal to reach the control module.
- 2
Wiring short or damaged harness
The cruise control input circuit wiring may have damaged insulation, corrosion, or a short to power that creates an abnormally high voltage condition.
- 3
Corroded or loose connector
Poor electrical connections at the cruise control switch connector or related module connections can cause intermittent high voltage signals.
- 4
Faulty cruise control module
The cruise control module or body control module may have internal failure preventing proper circuit voltage regulation.
How to Diagnose It
- 1
Check Faulty cruise control switch or stalk — The multifunction switch on the steering wheel or cruise control stalk may be malfunctioning, causing an excessively high voltage signal to reach the control module.
- 2
Check Wiring short or damaged harness — The cruise control input circuit wiring may have damaged insulation, corrosion, or a short to power that creates an abnormally high voltage condition.
- 3
Check Corroded or loose connector — Poor electrical connections at the cruise control switch connector or related module connections can cause intermittent high voltage signals.
- 4
Check Faulty cruise control module — The cruise control module or body control module may have internal failure preventing proper circuit voltage regulation.
How to Fix It
- 1
Inspect and test cruise control switch
Test the multifunction switch on the steering wheel using a multimeter to verify it produces correct voltage signals. Replace if voltages are out of specification.
- 2
Check wiring and connectors
Visually inspect the cruise control circuit wiring harness for damage, corrosion, or exposed conductors. Check all connectors for corrosion and ensure they are fully seated and secure.
- 3
Clean or replace connectors
Disconnect the cruise control switch connector and module connectors, clean with electrical contact cleaner, and apply dielectric grease before reconnecting. Replace connectors if pins are damaged.
- 4
Replace cruise control module if needed
If wiring and switches test normal, the cruise control module or body control module may require replacement. Have module reprogrammed or coded to the vehicle after installation.
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