Hello, this code sets when the Crankshaft Position sensor does not have a learned Variation by the engine computer. Since you have a no start condition, most likely the Crankshaft Position sensor is bad, the wiring to it has an issue, or the engine computer is faulty. When we replace a Crankshaft Position sensor, that is the time we will do the variation relearn procedure. Im assuming you have not replaced the sensor? Its abit odd youre not getting any other codes for the crankshaft sensor. During a failure of the sensor there will usually be a code like P0335 Crankshaft Position Sensor circuit fault, or P0336 Crankshaft Position Sensor Performance. Below are normal Crank Position sensor failures, so this one is somewhat worrisome.
This code suggests that the Engine computer (ecm) has lost its memory of the sensors learned variation.
So a couple possibilities here are, the battery is not maintaining a charge enough to keep the ecms memory alive, the wiring to the ecm has an issue where the keep alive voltage to the ecm has been disrupted (this can be a power to the ecm or a bad ground to the ecm), or the ecm itself has failed for some reason.
To do the Variation Relearn Procedure you need a scan tool that has the special function to do the procedure.
What else is strange, is usually after replacing a crankshaft position sensor the vehicle will start, it wont always run good until the relearn is done, but it will start.
Were there any other codes besides the P0315? And do you have your own scan tool and or multimeter? If you have a multimeter we can check to see if there are any blown fuses and if the engine computer is getting its keep alive memory voltage.
The 2nd diagram is an ECM fuse 15amp in the engine compartment fuse box on the driver side. Check that fuse first.
When you check that fuse, look at the pins where the fuse sits, are they corroded at all? Is there any white or green corrosion in the 2 pins that hold that fuse?
Also I assume the vehicle does crank over, just doesnt start?
Since the vehicle has to be up to operating temperature to do the Crankshaft Position sensor Variation Relearn, checking the sensors harness plug and the ecm power is going to be the first steps in this diagnosis.
https://www.2carpros.com/articles/how-to-use-a-voltmeter
https://www.2carpros.com/articles/how-a-crank-shaft-angle-sensor-works
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Aug 9, 2022 at 10:51 AM