So I just bought a 2009 G37XS with 116000k km (72k miles) a few days ago. On the drive home from picking it up I floored it from a stop in DS and the car had trouble shifting into 2nd gear. It did shift but it bucked pretty hard and went into a weird mode where every shift would be pretty violent (jerks the whole car every shift) UNTIL I shut the car off for 2 min. Once I do the car runs fine, smooth shifting like nothing happened.... UNTIL once again, you floor it from a stop (DS).

Now the first time this happened I don't think any lights came on. However, the second time the Service Engine Soon light came on along with Slip and VDC OFF. Same problem as the first time (trouble shifting into 2nd gear in ds, violent jerk, every shift will jerk the car until restarted).

Tried it a 3rd time with my father.... same thing (with SES, slip, vdc off lights) until car is restarted.

Plugged in a code reader and got P0335 crankshaft Position Sensor, Circuit Malfunction

Contacted the seller (private) said he never had this problem and recommended to do a reset. I did the ecu reset and the problem isn't as bad as before. The car now goes into 2nd gear (when flooring from a stop) without going into that weird mode where every shift is jerking the car. I tried this 4-5 times and it didn't throw any codes or affect the other shifts.

The problem is still kind of there, it has a hard time going into 2nd when flooring it from a stop but instead of violently bucking the car, it bucks but not as hard and is just really laggy and doesn't affect the other shifts after that, like it would before the ECU reset.

Its weird, its kind of like the car hits a wall (cuts fuel?) before it shifts.

From my research I found that:

*Crankshaft sensor could cause this, but then why didn't it throw another code like before (P0335)?

*Transmission needs new fluid? Car has 116000k km about 72k miles

*Transmission needs update?

*I also read something about engine harness wires?

Does anyone know why this is happening ? whats causing this?

 

Rusty, welcome to the site, sorry to hear of your frustrating start w/ this car
*Crankshaft sensor could cause this, but then why didn't it throw another code like before (P0335)? I'd try the below two items prior to this, @72k miles it would be a good idea to get the fluid serviced. If you are a DIYer here's a link that will help. I changed mine at 74k miles IIRC and it's shifting/performing well. The nice thing about this DIY is you also remove the pan so the sludge and metal shavings around the magnets can be cleaned up.
https://www.myg37.com/forums/d-i-y-i...rop-clean.html

The dealer should be able to run your VIN# and determine what (if any) updates have been done to your AT, this should help your overall AT behavior, G/L and hope you can start enjoying your new G.

*Transmission needs new fluid? Car has 116000k km about 72k miles

*Transmission needs update?

 

I'm experiencing the same exact problem along with the p0335 code. Only difference is I have an 08 5at. I'll return with an update once I change my fluid and check with the dealer about the transmission update.

 

It actually ended up being a faulty crankshaft sensor for me. The car ran perfectly fine after I replaced it.