P0504 on Chevrolet: How to Diagnose & Fix
Brake Switch "A"/"B" Correlation
2 Chevrolet models · 2 documented issues · 1 critical · $30-$180 repair
P0504 on Chevrolet by model: symptoms, diagnosis and fix
GM recalled 2004-2012 Chevrolet Malibu sedans (built May 16, 2003 through October 11, 2012) because increased electrical resistance in the Body Control Module (BCM) connection can cause voltage fluctuations in the Brake Apply Sensor (BAS) circuit. NHTSA's record states those fluctuations can cause the brake lights to behave incorrectly, among other conditions. This is a connector/wiring-interface defect at the BCM rather than a worn brake pedal switch, so a Malibu can exhibit the fault even if the brake switch itself has already been serviced. The campaign covered 2,440,524 vehicles in total across every model included in it (Malibu, Malibu Maxx, Pontiac G6 and Saturn Aura) — that figure is campaign-wide and is not a count of Malibus. NHTSA states that any of these failure conditions increases the risk of a crash.
Common Symptoms
- Brake lights not working correctly
How to Fix
The repair is free at any Chevrolet dealer under recall 14V252000. The dealer attaches the wiring harness to the BCM using a spacer, applies dielectric lubricant to both the BCM/harness connector and the Brake Apply Sensor/harness connector, and relearns the brake pedal home position. GM sent an interim owner letter on July 14, 2014 and the recall began August 18, 2014. Enter your VIN at nhtsa.gov/recalls to confirm whether your Malibu is still open for this remedy, or call GM customer service at 1-800-222-1020.
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Sources for this issue (1)
The brake lamp switch at the pedal is a known weak point on first-generation Colorado trucks. Owners report brake lights staying on, not coming on reliably, inability to shift out of park, or cruise control dropping out unexpectedly. Because the switch feeds several circuits, a single failure can create multiple confusing symptoms.
Common Symptoms
- brake lights stay on
- brake lights do not illuminate consistently
- cannot shift out of park
- cruise control inoperative
- battery drains overnight from brake lamps staying on
How to Fix
Inspect brake lamp operation first, then verify switch adjustment and continuity at the pedal assembly. Replacement of the brake light switch is usually straightforward and inexpensive, but technicians should also check for damaged pedal bushings or connector issues if symptoms persist. After replacement, confirm proper brake lamp operation and shift interlock release.
Sources for this issue (1)
P0504 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0504 mean on a Chevrolet?
P0504 stands for "Brake Switch "A"/"B" Correlation." Most vehicles use two independent brake switch signals (a normally-open and a normally-closed circuit, switch A and switch B). The PCM compares them and expects them to change state together when the brake pedal is pressed. P0504 sets when the two signals disagree (do not correlate), indicating one switch or circuit is faulty. On Chevrolet it is documented across 2 models: Malibu, Colorado.
What are the most common causes of P0504?
The most common causes of P0504 are: Failed brake light switch, Misadjusted brake switch (plunger gap), Wiring/connector fault on one of the two brake switch circuits, Blown brake-circuit fuse affecting one signal, Faulty PCM input. The specific cause varies by vehicle.
How much does it cost to fix P0504 on a Chevrolet?
Published repair estimates on Chevrolet range from $30 to $180 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0504 on a different make?
View P0504 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.