Tech Tips August 2014 (TIPS 0814)

TECH TIPS AUGUST 2014

TECHNICAL SERVICE BULLETIN

12 2015MY LEGACY/OUTBACK SEAT HEATER OPERATION OVERVIEW

The front seat heater system used in the 2015MY Legacy/Outback is a new design compared to prior systems. It utilizes a thermistor sensor which allows the front seats to remain at warmer temperatures more consistently than the prior system. The new system is very different due to the change in sensors. The seat heater system on 2014MY and prior Legacy/Outback is a thermostat sensor-based system which makes the front seats heat up periodically and then cool down until the sensor indicates a need to turn the element on again. When this sensor-based system is operating, the temperature increases until the sensor reads the heating element has reached approximately 50 degrees C (roughly 122 degrees F). At that point, the element is turned off until the sensor reads approximately 40 degrees C (104 degrees F). At that temperature reading, the element is turned back on again to re-heat the seat resulting in an approximate 18-degree range. This cycle continues as long as the seat heater switch is on in either the low or high position.

In comparison, the thermistor sensor used in the new system also has periodic on and off cycles, but the operating range (temperature difference) is much smaller with an upper limit temperature which is slightly lower. The new system turns on the element until the thermistor sensor reads approximately 38 degrees C (roughly 100 degrees F) then cycles the element off until the temperature (at the thermister) reaches approximately 37 degrees C (roughly 98 degrees F) before the element cycles on again, yielding only an approximate 2-degree range. As you can see, the upper and lower temperature range on the new system is significantly reduced. However, this is an apples and oranges comparison as the actual seat temperature felt is very similar. As you can see on the chart below, the average surface temperature of the front seat for each system ends up being very close. The RED line on the graph shows the temperature on front seat surface of the new 2015MY Legacy/Outback while the GREEN line represents the previous model year. You can see the fluctuations of the previous system have been virtually eliminated and the temperature stability enhancement the new system provides.

There are three levels of front seat heating available for 2015MY Legacy and Outback, HIGH (1), MID (2) and LOW (3). The difference among these modes is an upper limit temperature change of about 2 to 4 degrees C. Similar to the older system the speed at which the seat actually heats up varies with the level settings. The high setting will heat the seat the quickest, mid will increase the temperature more gradually and low will increase it at the slowest rate.

In contrast, the rear seat heater system used on 2015MY Legacy/Outback is a similar design as the previous model year but, the cycle and surface temperatures for those seats are lower than the front seats on previous model by a few degrees C.

Another operational difference between the old and new seat heater systems is how each functions in higher ambient temperatures conditions. Naturally, ambient temperatures which are at or above the upper limit of either system's sensor function may keep the seat heater from operating. Simply stated, if the ambient temperature inside the car is higher than the upper cycle limit for that sensor, the system will not allow the element to heat. This is not a malfunction; the seat heater system is operating as designed.

Should you receive a customer concern stating their seat heaters do not work, start your diagnosis by first confirming the conditions under which the system was reported to be inoperative. If the ambient temperatures were close to or higher than the seat heater sensor's upper limit (remember, inside vehicle temperatures will be higher than outside ambient temperature in most cases), the concern may be due to characteristic system operation. If this is not the case, diagnose the system using the applicable Service Manual. On the new 2015 Legacy and Outback, you can view the temperature of the thermistor sensor using the SSMIII as shown in the screen shot below. This data may be used to check if the sensor is functioning correctly or not.

15 2015MY LEGACY AND OUTBACK, KEYLESS ENTRY AUDIBLE SIGNAL FEATURE

Be advised, for 2015 MY Legacy and Outback models, the audible signal or "chirp" heard when locking and unlocking the doors feature is only available on models equipped with the Keyless Access with Push-Button Start system. The feature can also be turned on or off by the operator. Models with keyed ignitions no longer have the audible signal feature.

01 CHANGE TO SPARE TIRE RETAINING BOLT

Be advised that during the upcoming fall months, there will be a running change in production to the spare tire hold-down bolt on all FHI-built models. SIA built vehicles already incorporated a similar change starting with 2015 MY production. The "handle" portion of the bolt will change from metal to plastic as shown in the photo below. The current "metal" and new "plastic" version are interchangeable.

07 PASSENGER SIDE POWER WINDOW AUTO UP/DOWN FUNCTION

Have you had a customer complaint of the auto-up/down window function not working on a 2015 Legacy/Outback? On the 2015 Legacy and Outback, if the vehicle's battery is disconnected or becomes discharged, the auto-up/down feature must be re-initialized. If the front passenger's window is equipped with the auto-up/down function, it is necessary to repeat the same initialization procedure on that window switch. All Premium and Limited models have front passenger windows equipped with this feature. Additionally, if the power rear gate is open when the negative battery cable is disconnected, it too will need to be manually reset (closed) to be reinitialized. If you need information detailing the steps of the procedure please refer to STIS.

06 2015 LEGACY AND OUTBACK ELECTRONIC PARKING BRAKE CODES C1956 OR C1957

If you receive a customer complaint of a flashing Brake system warning light on their instrument cluster immediately following engine start, this may be resulting from a characteristic of the new electronic parking brake (EPB) system. Several notes on brake system warning light operation are outlined in the instruments and controls section of the appropriate owner's manual.

If the driver starts the engine at the exact same time as the electronic parking brake is still in process of applying or releasing, there is a possibility that a code C1956 and/or C1957 may set in the VDCCM. As a result the Brake warning lamp in the instrument cluster will be illuminated and flashing. This condition will clear itself with the next application (apply/release) of the EPB and the brake lamp will extinguish normally, however the code(s) will remain in the VDCCM memory. However, if the EPB is not cycled the flashing Brake warning lamp will remain on even if the ignition is cycled on or off including if the key is removed from the ignition.

If presented with this type of customer concern, first interview the customer to determine if the engine may have been started during application/release of the EPB. Once confirmed, check the VDCCM for one or both of the listed codes. If the customer confirms this may have occurred, the code(s) listed are present in the VDCCM memory only and the brake system warning lamp is functioning normally; the next step would be clear the VDCCM memory. Then explain to the customer how this condition occurred and how to avoid it in the future by either waiting until the EPB has fully applied/released before starting the engine or starting the engine and then applying/releasing the EPB. The owner's manual is a good reference for this discussion.

If you cannot confirm if the engine was started at the same time the EPB was applying/releasing or it remains unclear if this occured, then proceed with the troubleshooting for any code found in the VDCCM to ensure there is not a different cause for the reported condition using the appropriate service manual diagnostics.