C1225 indicates the brake warning lamp output circuit has detected a short to battery voltage (power) when the lamp should be off. This code is set when the controlling module sees the lamp circuit wired to constant power instead of being switched properly. The problem is in the lamp control circuit, not the brake system itself.
Damaged, chafed, or melted wiring in the brake warning lamp circuit contacting constant power sources is the most common cause. Inspect the harness near the instrument cluster and brake pedal area.
A shorted bulb or LED in the brake warning lamp assembly can create a direct path to battery voltage. Inspect and test the lamp element.
A connector in the brake warning circuit with bent pins, corrosion, or moisture can create an unintended short to battery power.
The instrument cluster often controls the brake warning lamp. Internal failure can cause a short at the cluster output stage.
Some vehicles use the BCM to drive the brake warning lamp. Internal failure in the output circuit can set this code.
The engine or ABS module may control or monitor this circuit. PCM failure is possible but uncommon—far less common than wiring or cluster issues.
The code indicates an electrical short, not necessarily a brake system failure. However, the underlying wiring issue should be diagnosed promptly—severe shorts can drain the battery and leave you stranded.
No. PCM failure is one of the least common causes of C1225. Most cases are resolved by repairing wiring, replacing the lamp assembly, or fixing a connector. PCM replacement should only be considered after all other circuit components are confirmed good.
Yes, if the bulb or LED has shorted internally. However, many vehicles use separate filaments for the lamp—check whether the brake warning lamp shares a bulb with the turn signals or other functions.
Yes, if the short condition still exists. The code will typically return immediately or within the next drive cycle once the module detects the fault again.