Magazine for the auto service professional
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Circle 119 on Reader Service Card 34 | September/October 2014 Being that today's vehicle systems are computer-managed, it stands to reason that when they have weird sensor or computer- related driveability problems, resetting the vehicle's computers may be the way to go. Resetting on-board ECUs Some technicians prefer removing the battery cables and jumping them for 30 minutes. Others like getting fancy and put- ting a one ohm 10 watt resistor in series and powering down the vehicle for a few minutes. The same is true of both strate- gies: A soft reset is known to work wonders. Some high-end scan tools that enable refashes, such as the Autologic, feature convenient help-lines. When calling the help desk after a failure refashing, they will recommend that the technician perform a soft reset frst. Further, many mobile diag- nosticians will not even agree to take the time to look at a vehicle unless a soft reset was done frst just to rule out a "computer glitch." Simply "deleting the DTCs" or "resetting adapts" does not solve the issue. Unlike computers, vehicles do not come with reset buttons. So, the soft reset remains the only way to get the job done. It also does not hurt that doing a soft reset helps vehicles set their monitors quicker for inspection purposes, too. It should be noted that as more and more vehicles require idle, steering angle, and other relearns, we do not want to do soft resets haphazardly, especially if we do not have the proper scan tools to perform these relearn procedures. 2011 Buick Lucerne 3.9L speed- ometer moves erratically A feet vehicle was dropped off due to a speedometer which would erratically report different speeds. The vehicle was test driven and it did not act up for a long time. When it did, the scan tool picked up that the Vehicle Speed Sensor (VSS) parameter identifcation data (PID) was giving the Connections Figure 2: Mitchell's Prodemand's color coded wiring diagrams helped speed the diagnosis, informing the technician that the direct in- puts of the VSS were directly to the TCM, so if there was a sensor, as opposed to a module issue, the wiring up to the module should refect a discrepancy on a labscope.