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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > NA Engine (non-turbo) / Drivetrain / Exhaust Modifications > N52 rough cold start with code 2A37 pointing to VVT/ESS sensor



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      01-23-2025, 07:01 PM   #1
bimmer_fmz
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N52 rough cold start with code 2A37 pointing to VVT/ESS sensor

Changed valve cover about 2 weeks ago. Consistently got the cold start roughness issue recently. The issue only exists at cold start, once engine is warmed up, there is no issue to restart until the next cold start at about 8 hours later.
The only code I got is 2A37, which is pointing to the ESS sensor. Before jump into a $400 sensor and another round of labor intensive valve cover gasket replacement, I want to make sure the sensor is failed.

I used Carley live data to monitor the VVT nominal and actual angles at different stages.
1. before engine start, everything is at ~45 angle
2. at cold start, actual angle jump to 179 immediately. and the nominal angle is in 30-60 range. Here is case that code shows up.
3. restart after engine is warm, both angles stay at 175 statically. same like the car is in limp mode.
4. cleared the code, restart, everything back to normal. both angles are aligned at ~23 at idling, and synchronized perfectly at any other conditions.

I also manually turn the valvetronic motor by #4 hex key, the live data shows consistent angle move in both CW and CCW directions. If I manually moved the angle to 175, the system can bring it back to 23 immediately once I start the car at warm.

I tested the valvetronic motor pin and motor outside shell, there is no shorts observed.

I don't have a test plan yet for the sensor by multimeter. It is really appreciated if anyone can provide suggestions. It's a 2009 328i convertible with N52 engine. I don't have a diagram for the sensor.

So far, looks like both valvetronic motor and sensor works well. The only thing I don't understand is the actual angle moves immediately to 180 from 45 at cold start. Is there something else made the car go to limp mode at cold start?

Any suggestions are really appreciated!
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      01-27-2025, 05:30 PM   #2
bimmer_fmz
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UPDATE: tried a few simple multimeter test for the ESS, didn't find any clear short or open issues. But, when I try to monitor the angle change when engine is cold, there is no reading change from the sensor, which is consistent with the issue only happens at cold start. So, most likely, the issue is coming from the ESS. Ordered new parts, and will give it a try by this week.
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