Checking Relay And 15-Supply

This troubleshooting only applies to vehicles that have trouble codes, referring to lost communication, for several of the following control modules:

• Transmission Control Module (TCM) (only for vehicles with automatic transmission).
• Engine control module (ECM).
• Supplemental restraint system module (SRS).
• Brake control module (BCM).

The vehicle should have start problems.

If this is the case, the probable cause is a damaged relay 15-feed. This relay supplies voltage to a number of functions that may affect the vehicle's functionality, primarily at start.

Remove the relay, located by the electrical distribution box in the engine compartment, and check its functionality.

To replace the relay, see:CENTRAL ELECTRICAL UNIT ENGINE COMPARTMENT

Remedy as necessary.

Fig 1: Locating Engine Compartment Fuse/Relay Box

Courtesy of VOLVO CARS CORPORATION