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DTC codes / GM codes / P1586

P1586 · GMCruise Control Brake Switch 2 Circuit

P1586 on GM vehicles means the powertrain control module (PCM) has detected an implausible signal from the second brake pedal switch circuit used by the cruise control system. The PCM expects the two brake switches to agree, and when the second switch stays open or closed when the first indicates a change, it flags this code because it cannot trust the brake release signal for cruise control.

SystemPowertrain
Code typeGM specific
SeverityLow
Fix difficultyIntermediate
AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

  • Cruise control will not engage or drops out as soon as you press the brake pedal
  • The cruise control indicator may flash or fail to turn on when you press the set button
  • Often no symptoms besides the warning light, with normal driving and braking otherwise unaffected
  • The brake lights may work normally because the primary brake switch circuit is separate
  • In some cases the transmission torque converter clutch may not lock up or may unlock unexpectedly

Common causes, most likely first

  1. Faulty cruise control brake switch 2 (the release switch on the brake pedal bracket)
  2. Misadjusted or loose brake pedal switch bracket causing the switch plunger to misread pedal position
  3. Worn brake pedal pad or missing rubber bumper that changes switch actuation
  4. Damaged or chafed wiring between the brake switch and the PCM
  5. Corroded or loose connector terminals at the switch or PCM
  6. PCM internal fault on the brake switch input circuit (rare)

How to diagnose and fix it

  1. Connect a scan tool and read live data for both brake switch inputs while pressing and releasing the brake pedal to confirm the second switch does not change state
  2. Inspect the brake pedal bracket, switch mounting, and rubber pad for looseness, wear, or missing pieces that would prevent proper switch actuation
  3. Check the switch adjustment by verifying the plunger fully extends and retracts with pedal movement, and adjust or replace the switch as needed
  4. Disconnect the battery and inspect the wiring harness from the brake switch to the PCM for chafing, corrosion, or loose pins, repairing as required
  5. Measure resistance and continuity on the brake switch 2 signal and ground circuits to rule out opens or shorts before condemning the PCM
  6. Clear the code and perform a road test with cruise control engaged, monitoring live data to confirm the brake switch 2 signal now agrees with switch 1
  7. If all circuits and the switch test good but the code returns, follow GM service information for PCM diagnostics and replacement only as a last resort

Why brake switch 2 fails without warning

  • The second brake switch is a dedicated cruise release input, so the brake lights can work perfectly while the cruise control still refuses to engage because the PCM never sees the release signal.
  • A missing or deteriorated rubber bumper on the brake pedal arm is a common cause that mimics a failed switch, and replacing the switch without the bumper leaves the code present.
  • Aftermarket floor mats or debris that restrict brake pedal return travel can hold the switch in the wrong state and set P1586 intermittently.
  • Technicians sometimes replace the cruise control module or the PCM when the real fault is a chafed wire in the steering column or under the dash near the brake pedal bracket.
  • This code does not disable the brakes or affect normal stopping, but it will prevent cruise control operation and may affect torque converter clutch strategy on some GM models.

Can I keep driving with P1586?

The vehicle remains safe to drive because the primary brake system and brake lights are unaffected, but cruise control will not work reliably. Avoid using cruise control until the fault is repaired, and address the code promptly if you rely on cruise for long highway trips.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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