Tech Tips April 2014 (TIPS 0414)

TECH TIPS APRIL 2014

TECHNICAL SERVICE BULLETIN

16 COLD WEATHER CVT OPERATION, ENGINE RPM, AND CABIN HEAT

Starting with 2010 Legacy and Outback CVT and continuing with each subsequent new model release (2012 Impreza 2.0, 2014 Forester, etc...), FHI incorporated logic into the TCM for it to consider the driver's request for heat as a factor in determining where to set the CVT turbine speed. The HVAC head unit supplies information through the CAN on the driver's request for heat based upon a combination of blower fan operation and temperature (blend door) settings. The TCM logic then translates these into a High heat request, a Low heat request, or No heat request. Depending upon the level of the request, the TCM then instructs the CVT to change the drive ratio to create a net increase in turbine speed (engine rpm) so that additional heat is supplied to the passenger cabin. As a result you may hear comments or concerns from customers during periods of cold weather. This is particularly true during extreme or long lasting cold weather events. These may include comments ranging from customers noting that the engine rpms seems to be staying higher, to the CVT not entering its regular final drive ratio, to a concern that the CVT is hesitating (again not advancing to its regular final drive ratio). In each of these cases a detailed interview and review of the customer concern found that the symptom the customer observed was that the engine rpms were higher than the customer had seen previously (during warmer weather). The reason in each case was simply cold weather prompting an increased demand for cabin heat by the driver which resulted in the engine rpms being kept high to provide that heat. This was easily verified during similar cold conditions by turning the blower fan to the OFF position for several seconds while cruising at a steady speed in a fully warmed car and watching the resultant drop in rpms. If a customer reports a concern with higher rpm operation as a result of this logic and wants to reverse that effect, recommend that they reduce the temperature setting (or turn the blower fan to OFF) until it has the desired effect on engine rpm. Either of these actions will reduce or eliminate the input to the TCM that results the rpm increase. Otherwise simply explain that this is characteristic operation of the engine and transmission during cold weather resulting from the vehicle trying to meeting the driver's request for more heat based upon the HVAC temperature and blower settings.

12 2014 FORESTER POWER REAR TAILGATE

Should you receive a customer complaint of the power rear tailgate not working properly and you have checked the system for Diagnostic Trouble Codes and found a DTC B250F (Rotation Sensor Failure), make sure the rear gate stays are not bent at the attachment bracket as shown in this photo to the right. If this condition is confirmed, the gate stay will need to be replaced. Do not attempt to repair the bent bracket.

02 DISCOLORATION OF CYLINDER WALLS

The SOA Techline and Quality Assurance sections of the Service Department have recently had inquiries regarding cylinder wall discoloration noticed during installation of the updated piston rings.

In some cases, the Technician also reports measurements are out of specification when measuring the cylinder bore. It is required per the Service Manual that the cylinder bore must be checked at 68 degrees Fahrenheit, otherwise some variations are normal. The photo to the right is an example of this discoloration. It is in no way harmful to install the updated piston rings and use the existing block.

All of the Oil Control Ring TSBs have been recently updated on STIS with additional helpful information based upon field feedback, please make sure to review all of the enhancements. We frequently encourage all technicians to download the very latest Service Bulletin from STIS before performing it to ensure they have the latest information available.