Magazine for the auto service professional
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14 | September/October 2014 Tech tip Remote vehicle start is here to stay Remote vehicle start (RVS) systems have been used on several GM models since 2004. The RVS system utilizes the remote control door lock receiver (RCDLR), the body con- trol module (BCM), and the engine control module (ECM). To start the car from up to 195 feet away, the driver presses the lock button frst, and then the RVS button on the keyless entry transmitter. Some vehicles do not require pressing the lock button frst. Consult the owner's manual for vehicle specifc information. The turn signal lights will fash briefy to indicate that the vehicle has received the remote start command. The engine will then start, and will run for 10 minutes. An additional 10 minutes can be requested by repeating the transmitter button commands during or after the initial 10 minute run cycle. Vehicles with automatic climate con- trol will regulate the interior temperature to the last requested setting. The engine can be shut off during an RVS event by pressing the remote start button on the transmitter or turning on the hazard fash- ers or cycling the ignition key on, then off. When the RCDLR receives a remote start command from the keyless entry transmitter, it sends a serial data message to the BCM requesting a remote start. The BCM checks an internal list of RVS inhibit conditions that it monitors before send- ing a serial data remote start request to the ECM. If any of the inhibit conditions are active (such as the hood or trunk are open), the BCM does not send the remote start request to the ECM. Once the ECM receives the remote start request from the BCM, it checks its own internal list of monitored RVS inhibit conditions. If the ECM detects no active inhibit conditions, it will start the engine. Once started, the ECM can shut down the engine if it detects low oil pressure, excessive rpm, or high coolant temperature. Diagnosing an inoperative RVS system is not diffcult if you take an organized approach to the problem. First, verify proper operation of the keyless entry func- tions. If the keyless entry system is not working, correct that problem frst, and then test the RVS system again. Next, make sure the RVS system has not been inadver- tently disabled by the driver. RVS can be turned on and off in the "vehicle personalization" menu. Navigating The Tech Bench