Cruise Control/Brake Switch A Circuit Low
The cruise control/brake switch circuit is detecting a low voltage signal, indicating the switch is not sending the proper electrical signal to the engine control module. This prevents the cruise control system from functioning correctly and may also affect brake light operation if the same switch controls both functions.
What You Might Notice
- Cruise control completely inoperative or won't engage
- Erratic cruise control behavior (set, resume, or acceleration functions failing)
- Cruise control turns on but doesn't actually control speed
- Brake lights not functioning if brake switch is defective
- Missing cruise control functions like accel or resume buttons not working
Most Common Causes
- 1
Defective Brake Switch
The cruise control/brake switch has failed internally or has worn contacts, preventing proper voltage signal transmission to the ECM.
- 2
Wiring Issues
The wiring harness connected to the brake switch is pinched, chafed, corroded, or has an open circuit, breaking the electrical connection.
- 3
Brake Switch Adjustment or Installation
The brake switch is not properly adjusted, out of its mount, or installed incorrectly, preventing it from making proper electrical contact when the brake pedal is engaged.
- 4
Engine Control Module (ECM) Fault
The ECM has developed an internal short circuit or open that prevents it from properly reading the brake switch signal voltage.
How to Diagnose It
- 1
Check Defective Brake Switch — The cruise control/brake switch has failed internally or has worn contacts, preventing proper voltage signal transmission to the ECM.
- 2
Check Wiring Issues — The wiring harness connected to the brake switch is pinched, chafed, corroded, or has an open circuit, breaking the electrical connection.
- 3
Check Brake Switch Adjustment or Installation — The brake switch is not properly adjusted, out of its mount, or installed incorrectly, preventing it from making proper electrical contact when the brake pedal is engaged.
- 4
Check Engine Control Module (ECM) Fault — The ECM has developed an internal short circuit or open that prevents it from properly reading the brake switch signal voltage.
How to Fix It
- 1
Replace Brake Switch
Remove the defective cruise control/brake switch located near the brake pedal and install a new OEM or quality replacement switch, ensuring proper adjustment so it makes contact when brakes are applied.
- 2
Inspect and Repair Wiring
Check the wiring harness connected to the brake switch for damage, corrosion, or loose connections. Repair or replace damaged sections and ensure all connectors are clean and fully seated.
- 3
Adjust or Reinstall Brake Switch
Remove the brake switch and reinstall it correctly, adjusting it so the plunger properly contacts the brake pedal and the electrical connection is made when brakes are applied.
- 4
Test and Replace ECM if Needed
After confirming the brake switch and wiring are functioning correctly, have the ECM tested for internal faults. If faulty, the ECM may need to be replaced or reprogrammed by a dealer.
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