Code Definition

B0688 — Security system warning lamp Circuit high

System: Body  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About B0688

B0688 is a generic (obd-ii standard) body diagnostic trouble code. It belongs to the B-prefix family of codes, which covers body, interior, airbag, or comfort-electronics faults.

When B0688 is stored, the module has detected a signal or supply voltage higher than the expected operating range.

Scanning & clearing: Body (B) codes are often stored in the body control module, airbag module, or climate module. A basic OBD-II tool usually will not read body codes — an enhanced or OEM-level scan tool is typically required.

Because B0688 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

DTC B0688 is a generic body code that indicates the body control module or security system module has detected a higher-than-expected voltage on the security system warning lamp output circuit. The security warning lamp is normally driven by a low-side driver inside the BCM or security module — when commanded on, the driver pulls the circuit to ground, completing the path through the bulb (or LED) to switched ignition power. The module monitors the voltage on the driver pin and expects to see a low voltage when the lamp is commanded on and battery voltage when commanded off. The code sets wh...

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