Got a letter from Ford saying that there is a glitch in the diagnostic system (DTC P0315). The code apparently pops up and generates what CARB considers a failure during an emissions test. Ford says the emissions are unchanged and, I guess, the code generates a false positive. (Hello, VW?). Ford says "nothing to see here. But....if your Mustang fails an emission check because of the code bring it in with the letter-anytime within the next 10 years".

Has anyone else dealt with this? Maybe go in early and have the code cleared now? Excuse me but I'd really hate to have a future sale bollixed because the code wasn't cleared years earlier and it wouldn't pass an emission test. In California, the SELLER has to present a clean emissions test. I really don't want this hanging over into an uncertain future.

 

Provided the '16 ODBII codes are the same as '13, it looks like some correction factors are not being learned. After resetting the code (or pulling the battery cable to clear all of the KAL (keep alive memory), try three closed-throttle, non-braking, de-fueled decelerations in the 60 to 40 mph range after exceeding 60 mph .




About P0315 (from 2013):

Rough Road Detection

The Misfire Monitor includes a Rough Road Detection (RRD) system to eliminate false misfire indications due to rough road conditions. The RRD system uses data from ABS wheel speed sensors for estimating the severity of rough road conditions. This is a more direct measurement of rough road over other methods which are based on driveline feedback via crankshaft velocity measurements. It improves accuracy over these other methods since it eliminates interactions with actual misfire.

In the event of an RRD system failure, the RRD output will be ignored and the Misfire Monitor will remain active. An RRD system failure could be caused by a failure in any of the input signals to the algorithm. This includes the ABS wheel speed sensors, Brake Pedal sensor, or CAN bus hardware failures. Specific DTCs will indicate the source of these component failures.


A redundant check is also performed on the RRD system to verify it is not stuck high due to other unforeseen causes. If the RRD system indicates rough road during low vehicle speed conditions where it is not expected, the RRD output will be ignored and the Misfire Monitor will remain active.


Profile Correction


"Profile correction" software is used to "learn" and correct for mechanical inaccuracies in the crankshaft position wheel tooth spacing. Since the sum of all the angles between crankshaft teeth must equal 360o, a correction factor can be calculated for each misfire sample interval that makes all the angles between individual teeth equal. . The LDR misfire system will learn one profile correction factor per cylinder (ex. 4 correction factors for a 4 cylinder engine), while the HDR system will learn 36 or 40 correction factors depending on the number of crankshaft wheel teeth (ex. 36 for V6/V8 engines, 40 for V10 engines).


The corrections are calculated from several engine cycles of misfire sample interval data. The "mature" correction factors are the average of a selected number of samples. In order to assure the accuracy of these corrections, a tolerance is placed on the incoming values such that an individual correction factor must be repeatable within the tolerance during learning. This is to reduce the possibility of learning corrections on rough road conditions which could limit misfire detection capability and to help isolate misfire diagnoses from other crankshaft velocity disturbances.


To prevent any fueling or combustion differences from affecting the correction factors, learning is done during decel-fuel cutout. This can be done during closed-throttle, non-braking, de-fueled decelerations in the 60 to 40 mph range after exceeding 60 mph (likely to correspond to a freeway exit condition). In order to minimize the learning time for the correction factors, a more aggressive decel-fuel cutout strategy may be employed when the conditions for learning are present and are typically learned in a single 60 to 40 MPH deceleration, but can be learned during up to 3 such decelerations, or over a higher number of shorter duration decelerations..


For Hybrid Electric Vehicles profile is learned by using the electric drive to spin the crankshaft on the first engine shutdown during which time profile is calculated.


Since inaccuracies in the wheel tooth spacing can produce a false indication of misfire, the misfire monitor is not active until the corrections are learned. In the event of battery disconnection or loss of Keep Alive Memory the correction factors are lost and must be relearned. If the software is unable to learn a profile after three 60 to 40 mph decels, a P0315 DTC is set.

 

Thanks, I had no idea what the problem was addressing. Does anyone know if I can lean on the dealer to have it fixed or just hope-hope-hope it doesn't crop up when trade in/sales time comes around?