The P0315 code appears when the powertrain control module (PCM) sees that there is a variation between the actual value and the value stored in the crankshaft position reference points.
P0315 is a trouble code indicating that the crankshaft position system variation has not been learned. The point exceeds the limit, so the computer detects and throws this error code.
Communication Between CKP Sensor and PCM
In most cars, the PCM uses crankshaft position information to correctly determine spark timing. This position is detected by the CKP sensor.
CKP sensor It is stationary and works in conjunction with a toothed ring attached to the crankshaft. When the reluctor ring approaches the sensor, it interrupts its magnetic field, causing a signal to be sent to the PCM.
If the PCM detects an incorrect relationship between the crankshaft position sensor (CPK) and its own reference, the P0315 code is set.
In other words, when the engine is running, the PCM measures the difference between the crankshaft position reference points. These measurements are compared to a reference stored in the PCM.
If the deviation exceeds the calibrated percentage, a fault code is stored. In general, This is an electrical circuit failure. Although mechanical problems can also affect this code depending on the vehicle manufacturer.
Very often when this code is set the engine will not start. If the engine starts, it is likely to run very poorly.
What Exactly Does Code P0315 Mean?
Fault code P0315 is called “Unlearned crankshaft position (CKP) system variation“. It may have other different descriptions depending on the brand, but they refer to the same problem.
Error code P0315 It is a generic code and is related to the communication between the crankshaft position sensor and the powertrain control module.
The computer present in the vehicle measures the value or reference points between the Crankshaft position sensor CKP and the value already stored in the Power Train Control Module.
If after the comparison the computer sees data higher than the calibrated percentage, this code P0315 is set. The problem mainly points to the electrical circuit, but there may also be other reasons.
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Causes of Code P0315
The P0315 code can appear for several reasons, which are the following:
- The crankshaft position sensor wiring is defective.
- The crankshaft position sensor was damaged.
- The timing belt is broken.
- The powertrain control module is not working properly.
- The CKP sensor connector is defective.
- Timing components are damaged.
- The battery is disconnected without the memory-saving device.
- The wiring connecting the crankshaft position sensor and the PCM is burned or disconnected.
- Reprogramming the powertrain control module with outdated software
Symptoms of Code P0315
Common symptoms associated with code P0315 are the following:
- The Check Engine light comes on.
- Difficult start.
- Ignition failure.
- The motor does not start.
- If you do start the engine, it will have a rough and poor idle.
- Safe mode activated.
In some cases, the vehicle’s fail-safe mode may be activated, making it difficult to drive. Code P0315 symptoms appear depending on the root cause of the problem.
Depending on the make and model, the engine control unit may use the CKP sensor to evaluate the position and speed of the engine. Therefore, if P0315 is activated, the engine will run, but not at maximum efficiency.
In this case, you may experience difficulty starting, rough idling, or poor acceleration. We recommend that you do not start the car in these conditions. You run a high risk of the failure getting worse and more expensive.
Steps to Diagnose the P0315 Code
Steps to diagnose and fix the P0315 code
Step 1: In the diagnosis, you must first look for the technical service bulletins according to the vehicle. The problem can be known and it will save you a lot of time and money.
Step 2: Start by scanning the vehicle for the P0315 code. Now delete all the codes so you can test and see if the code appears again. If the problem is resolved here, it means that the P0315 code was intermittent and disappeared.
Step 3: If the code appears again, it means you need to inspect the engine further. Locate the crankshaft position sensor in your car and start looking for wires, scuffs, rubbing, or anything that could damage the vehicle.
Step 4: Now examine all the terminals by disassembling the connectors. If you see any change in their color or anything, clean them. They can burn or corrode. The correct way is to clean them using electrical contact cleaner and a plastic bristle brush.
Step 5: Replace or repair anything you find damaged in the CKP sensor circuit. This includes connections, cables, relays, fuses, etc.
Step 6: Now erase the codes from memory and test the car again.
Test the CKP sensor
Step 7: If the code continues to appear, it is time to check the sensor. Take a close look at the sensor, as well as the components related to it. Pay attention to the point where it connects to the timing component on the engine. Is it working correctly? If you feel there is any damage, replace it.
Step 8: Then, connect the scan tool to the vehicle’s diagnostic port and retrieve the stored fault codes.
Now check both the voltage and ground signals. You should also check the signal on the third cable, which is the one that communicates with the PCM.
Disconnect the electrical connector from the CKP sensor and test it according to the manufacturer’s recommendations, using a multimeter. Replace the sensor if the resistance values do not meet specifications.
If the values you have reviewed for the CKP circuit meet the values proposed by the manufacturer, continue with the next step.
Always remember that the quality of the replaced part is very important, as poor-quality components usually increase problems later.
Step 9: Then check if the timing chain/belt is in good condition and not loose. In case of any type of damage, you must proceed to change it.
After mounting any new component, you should reset the code to test if it is gone or not. In most cases, the code disappears after proper installation of the mentioned parts or cleaning of the components.
If in your case you have an oscilloscope available for testing, you can apply the following steps:
Step 1: Connect the positive test lead of the oscilloscope to the signal lead of the CKP harness and connect the negative lead to the CKP ground circuit.
Step 2: With the transmission in park or neutral and the engine idling, observe the waveform on the oscilloscope. Focus on any unexpected spikes or dips in the waveform pattern.
Step 3: If you notice spikes or glitches, gently move the wiring harness and connector while observing the waveform pattern. This way you check if there is a weak connection, bad contact or a damaged sensor.
Step 4: Observe the voltage blocks in the waveform pattern. If you notice one of these blocks missing, it is an indication that there is some mechanical problem with the ring gear teeth.
Step 5: Also check the CKP magnetic tip for excessive metal residue and clean it if necessary. If the waveform is normal, go to the next step.
Step 6: Now reconnect the oscilloscope test leads to the same circuits near the PCM connector and observe the waveform pattern. If you find a deviation, there is most likely an open circuit or short circuit between the CKP connector and the PCM connector.
If no open or short circuits are found, the problem with error P0315 may be a faulty PCM or its programming.
Common Errors When Diagnosing Code P0315
This code can be caused by mechanical or electrical problems, so the most common error is mixing these two without performing a proper diagnosis.
Focusing on an electrical diagnosis, when the problem is a broken chain, is a worthy example. Or change the sensor without checking the wiring, which is very common.
The important thing is not to repeat these errors and carry out a correct diagnosis to identify the fault. Do not carry out repairs or change parts without making the diagnosis.
How to Fix Code P0315
Remember, repairs must be carried out according to what the diagnosis shows. These are some of the repairs you can carry out:
1. Crankshaft position sensor
If the problem lies with the crankshaft position sensor, you need to replace it to resolve the problem. Sensors are generally not repairable, just replaced with another original OEM.
Sometimes the crankshaft position sensor wiring is burned out, so changing it will also fix the problem.
3. Related electrical components
A circuit is not made up of cables alone. In the diagnosis, you will be able to notice that the fault is in a fuse or a bad connection. You must carry out the corresponding repair or replacement.
4. Timing Belt/Chain
By checking the condition of the timing belt or chain, you will be able to know if it needs to be changed. Remember that this element has a stipulated maximum mileage and must be respected to avoid major damage to the engine.
If the belt is in good condition, but its mileage is still close to expiring, the ideal is to change it, taking advantage of the intervention.
5. Powertrain control module
Although not common, the code can be activated if the PCM Module has problems. In this case, you should check it with a specialized technical service and change it if necessary.
How Serious Is Code P0315?
Never take this code lightly. This code can be considered very dangerous because it can damage the engine. Do not try to drive the car in these conditions.
Take your car immediately for inspection to carry out a good diagnosis and repair the problem.
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The most common misdiagnosis of the P0315 code may be to take it as a problem of mechanical origin when it is an electrical problem and vice versa.
Therefore, you could end up replacing the wrong component. You must be very careful when making the diagnosis.
If you consider that you cannot make this diagnosis, it is best to take the car to your trusted mechanic. Since this error code is so dangerous for your engine, this would be your best decision.
If you want to know other articles similar to Code P0315. Unlearned Crankshaft Position (CKP) System Variation you can visit the category Fault Codes.