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Why was that suggestion made? A relearn is done after the sensor is replaced and I don't believe even replacing one on this vehicle calls for a relearn. Here are the directions for replacement of the crankshaft position sensor. Note at the end is where it indicates a relearn and none is mentioned.
As far as the crank sensor, here are a few links to help. The first explains what it does, the second explains symptoms, and the third shows in general how one is replaced.
Here are the directions specific to your vehicle:
CRANKSHAFT POSITION (CKP) SENSOR REPLACEMENT
Crankshaft Position Sensor Replacement
Caution: Refer to Battery Disconnect Caution in Service Precautions.
1. Disconnect the negative battery cable.
2. Disconnect the crankshaft position (CKP) sensor electrical connector.
3. Remove the CKP sensor bolt.
4. Remove the CKP sensor.
Notice: Refer to Fastener Notice in Service Precautions.
1. Install the CKP sensor with the bolt.
Tighten the CKP sensor bolt to 6.5 Nm (58 lb in).
2. Connect the CKP sensor electrical connector.
3. Connect the negative battery cable.
I'm not saying it couldn't be the sensor, but since it got worse since it was repaired, I would start by checking to see if maybe something like a vacuum line was left off or something wasn't plugged in.
Let me know if this helps or if you have other questions.
Images (Click to enlarge)
Monday, August 5th, 2019 AT 11:34 AM