P0170 & P0173 Codes on 2006 W203 C230 2.5L

May 31, 2018 | 12:43 PM

Irakli Kikvadze

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W203 C230

P0170 & P0173 Codes on 2006 W203 C230 2.5L

Hello, I got P0170 & P0173 Codes for long time already.
Typical diagnostic and service guys (Even MB service center in my country) cant identify exact problem and all they offer are changing parts one by one, starting from MAF sensor ending to even engine itself.

I did some DIY reserch and OBD diagnostic to find out the reason but still cant get correct direction.
All I know is that both Fuel Trims are involved that excludes some bank related parts. Also I got rich condition as LTFT-s are negative.
Here are two data graphs from my ordinary BT OBD II reader:
1. With cleared error codes showing STFT's at -25% and LTFT''s at 0%

2. When LTFT got negative and STFT back to 0 (still not stable +-10%)
It took about 10-15 min to slowly get to -9%, maximum I have seen is -11%.

MAF reads 4 to 5 g/s on idle and MAP ~20%, that looks normal I guess.
Did volumetric efficiency test on WOT and got about 85-90%.
IAT and ECT looks also normal to me.
Upstream wideband O2 sensors oscillates from -128mA to 128mA and lambda is normally set to 1. (Have no idea why it sometimes hit 1.5 or even 2.0 value).
Downstream O2 sensors oscillates from 0.1v to 0.9v also fine.
Except of Lambda randomly hitting 2.0 value, Absolute Load Value sometimes somehow reads up to 120-180%. As far as I know it is same VE calculation and on non-turbo motors it should go 95-100% MAX.
No other error codes are stored so far.
Also not sure if it's my obd lacking some data or its related to those codes, but at Readiness Monitor all supported monitors is completed except of: Catalyst, Evaporative System and Oxygen Sensor.

Any ideas what I can do next to identify/fix this problem, did anyone had same issue or experience?
Attached Freeze Frame excel file in case.

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