P0576Cruise Control Input Circuit Low
The cruise control input circuit is reading a voltage lower than the expected range, usually from a short to ground.
Definition
The PCM or cruise module supplies a reference voltage to the cruise control input circuit and reads the returned signal to decode switch commands. P0576 sets when that signal stays below the minimum plausible voltage, which usually means the circuit is shorted to ground or a switch contact is stuck closed. The module disables cruise control as a failsafe, so the system will not engage or drops out; there is no effect on engine operation or emissions and the MIL usually remains off.
Common causes
- Cruise switch signal wire shorted to ground (chafed harness in the column or dash)
- Stuck or internally shorted cruise control switch
- Failed clockspring shorting the signal circuit
- Liquid intrusion in the switch or column connector pulling the signal low
- Corroded connector creating a low-resistance path to ground
- Faulty module input circuit (rare)
Common misdiagnoses
- Replacing the brake light switch
- Replacing the cruise actuator or servo
- Replacing the PCM before checking for a simple harness short
- Replacing the vehicle speed sensor
Troubleshooting steps
1.Measure the input circuit voltage
Back-probe the cruise input at the module with the key on; a reading near 0 V with no buttons pressed confirms the circuit is held low.
2.Isolate the switch from the circuit
Disconnect the cruise switch; if the voltage rises to the reference value, the switch (or clockspring path through it) is shorted.
3.Test the harness for a short to ground
With both ends disconnected, ohm the signal wire to chassis ground; anything other than open (OL) indicates chafed wiring to find and repair.
4.Check the clockspring
Verify the spiral cable circuits are not shorted together or to ground, wiggling the steering wheel while measuring.
5.Confirm the repair
Clear the code, verify each cruise button produces its correct voltage step, and road test with cruise engaged.