Body Control System Diagnosis
B2753 - Horn Relay Coil Circuit HighSchematic:
CIRCUIT DESCRIPTION
The body control module (BCM) controls the operation of the horn for the security system and remote keyless entry (RKE) functions. Circuit 28 is grounded by the BCM when horn operation is desired. Normal operation of the horn is performed by the horn switch grounding the horn relay and is not controlled by the BCM.
DTC PARAMETERS
^ Horn operation is requested by BCM (output is On)
^ Circuit 28 shorted-to-battery voltage
^ Service (wrench) light will illuminate
DIAGNOSTIC AIDS
^ When a shorted-to-battery voltage condition exists in circuit 28 and the BCM requests operation of the horns, the BCM will attempt to switch circuit 28 to ground. High current flow will result and the BCM output will go into a protective state. The BCM output will not allow itself to be activated for as much as 3 minutes. The BCM is protected. Damage will not result.
^ Inspect wiring harness for damage. Check for broken or chafed insulation.
^ Check for poor connection at the rear defrost switch.
^ If fault is suspected to be intermittent, wiggling harness wiring may help in locating fault.
^ Check for poor connection at BCM. Inspect harness connectors for backed out terminals, improper terminal mating, broken connector locks, improperly formed or damaged terminals and poor terminal-to-wire connection (terminal crimped over wire insulation and not conductors).
TEST
Diagnostic Chart:
