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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1513 (Lighting Systems) >> Diagnostic Information and Procedures >> DTC B2578 >> Circuit Description

Circuit Description

WARNING: This page is about a different car, the 2004 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

The BCM monitors the RF turn signal circuit in order to determine the status of the turn signal switch. If the BCM detects an oscillating voltage on the RH turn signal monitor circuit, the BCM interprets this as a RF turn signal ON request from the turn signal switch. The BCM will then de-energize the RH DRL relay, which will disable the RF turn signal lamp (which is ON for the DRL), this allows the RF turn signal to flash. If the BCM does not detect an oscillating voltage on the RH turn signal monitor circuit, the BCM interprets this as the RF turn signal being OFF. The BCM will then energize the RH DRL relay and continue normal DRL operation. The BCM monitors the RH turn signal monitor circuit and determines how long voltage is applied. If the voltage is applied for longer than expected, a malfunction is present and a DTC will set.