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System: Chassis (C-Code) Coverage: SAE Standard (Generic) Fault Family: brake_pedal_switch_stop_lamp_circuit

Code C0040: Brake Pedal Switch A

Diagnostic & Technical Explanation
Code C0040 (Brake Pedal Switch A) sets when the module sees an implausible state from the brake pedal switch(es) that both illuminate the stop lamps and tell the ABS/cruise/shift-interlock systems the brake pedal is applied -- the switch stays closed, stays open, or the two redundant switch channels disagree with each other. A misadjusted switch plunger, a worn switch contact, or corrosion at the switch connector near the pedal bracket are the common causes. Because this switch also feeds the stop lamps and brake-transmission shift interlock, a fault here can cause symptoms well beyond ABS, from stuck-on brake lights to a shifter that will not release from Park.

Probability-Ranked Repair Procedures (4 Ranked Fixes)

Rank #1

Adjust brake pedal switch plunger clearance

Easy DIY
Parts Estimate: $3.0–$15.0 USD Labor Estimate: 0.3 Shop Hours
  1. Locate the brake pedal switch mounted on the pedal bracket above the pedal arm
  2. Loosen the switch locknut and adjust plunger contact per the service manual clearance spec
  3. Pull the pedal fully rearward to auto-adjust the switch on platforms that support it
  4. Verify stop lamps and scan tool brake switch PID respond correctly to pedal travel
Required Replacement Parts: 🔧 Brake pedal switch
Rank #2

Inspect brake pedal switch connector

Easy DIY
Parts Estimate: $5.0–$20.0 USD Labor Estimate: 0.3 Shop Hours
  1. Unplug the switch connector and inspect pins for corrosion
  2. Clean with electrical contact cleaner and reseat the connector
  3. Confirm both switch channels toggle together with a multimeter
  4. Clear the code and verify stop lamp operation
Required Replacement Parts: 🔧 Electrical contact cleaner
Rank #3

Replace brake pedal switch

Moderate DIY
Parts Estimate: $15.0–$60.0 USD Labor Estimate: 0.5 Shop Hours
  1. Disconnect the battery negative terminal
  2. Rotate and remove the switch from the pedal bracket
  3. Install the replacement switch and adjust plunger clearance to spec
  4. Clear codes and confirm correct stop lamp and brake-applied signal operation
Required Replacement Parts: 🔧 Brake pedal switch
Rank #4

Repair stop lamp/brake switch circuit wiring

Professional Required
Parts Estimate: $15.0–$60.0 USD Labor Estimate: 1.0 Shop Hours
  1. Trace the harness from the switch to the module and stop lamp fuse
  2. Check for chafing near the pedal bracket and steering column
  3. Repair with solder and heat-shrink where damaged
  4. Verify both switch channels and stop lamps function correctly
Required Replacement Parts: 🔧 Automotive wiring repair kit (solder + heat-shrink)

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