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DTC codes / C01xx · Brakes, steering and suspension / C0136

C0136Stop Lamp Switch Circuit

C0136 sets when the antilock brake system (ABS) control module detects an implausible signal from the stop lamp switch circuit, meaning the brake pedal position input does not match expected voltage patterns during key-on or driving. The module compares the stop lamp switch state against vehicle speed and other brake inputs, and flags the circuit when the signal stays high, stays low, or toggles erratically outside normal parameters.

SystemChassis
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaBrakes, steering and suspension

Symptoms you may notice

  • ABS warning light illuminated on the dashboard, often with no other noticeable change in braking feel
  • Traction control or stability control warning light also on because those systems share the stop lamp switch input
  • Brake lights that stay on continuously or fail to illuminate when the pedal is pressed
  • Cruise control that will not engage or disengages unexpectedly when the brake pedal is touched
  • Gear selector that will not move out of Park on vehicles that use the brake switch as an interlock input
  • Often no symptoms besides the warning light, with normal brake pedal feel and normal stopping performance

Common causes, most likely first

  1. Faulty or misadjusted stop lamp switch at the brake pedal, including a worn plunger or cracked internal contact
  2. Blown fuse or corroded terminals in the stop lamp switch power feed circuit
  3. Damaged, chafed, or disconnected wiring between the stop lamp switch and the ABS control module
  4. Poor ground connection at the switch mounting or at the body ground point shared with the ABS module
  5. Brake pedal position sensor or secondary brake switch out of adjustment on vehicles with redundant pedal inputs
  6. Failed ABS control module input circuit, though this is far less common than switch and wiring faults
  7. Aftermarket LED brake light bulbs or trailer wiring that alter the current draw and confuse the switch signal

How to diagnose and fix it

  1. Verify the brake lights operate correctly with the pedal pressed and released, then check the stop lamp switch adjustment and mounting
  2. Scan all modules for stored codes and freeze-frame data, then clear codes and test-drive to confirm C0136 returns
  3. Inspect the stop lamp switch fuse and test for battery voltage at the switch connector with the key on
  4. Back-probe the switch signal wire at the ABS module connector and compare voltage with pedal released and pressed
  5. Check resistance to ground on the switch ground circuit and inspect the harness for chafing near the pedal assembly and kick panel
  6. Replace the stop lamp switch if voltage signals do not toggle correctly, then recheck switch adjustment and clear codes
  7. If the switch and wiring test good, perform a continuity and load test on the signal circuit to the ABS module before condemning the module

Stop lamp switch faults that mimic ABS failures

  • A stop lamp switch that tests fine with a multimeter can still set C0136 because the ABS module looks for a specific voltage transition timing that a worn contact cannot deliver under load.
  • Aftermarket LED brake light bulbs and trailer wiring adapters commonly alter the current draw on the stop lamp circuit and cause the ABS module to misread the switch state, so check for recent electrical add-ons first.
  • The stop lamp switch feeds the cruise control, shift interlock, and stability control systems on many vehicles, so a single switch fault can set codes in several modules that look unrelated.
  • A misadjusted switch that works perfectly in warm weather can fail only in cold temperatures when the plunger retracts differently, so test the circuit after the vehicle has sat overnight.
  • Technicians who replace the ABS module without back-probing the switch signal at the module connector often find C0136 returns because the actual fault was a chafed wire in the pedal harness.

Can I keep driving with C0136?

The vehicle remains safe to drive in most cases because the base hydraulic brakes are unaffected, but you should avoid relying on cruise control and be aware that the ABS and stability control systems may be disabled while the light is on. Have the fault diagnosed promptly, especially if the brake lights stay on continuously, because that can drain the battery and confuse following drivers.

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 all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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