2017 GLS550 Turbo A Underboost CEL
Re: 2017 GLS550 Turbo A Underboost CEL
If it's a Xentry-only test, let me know if you have any time Sunday to check it out either here or I can bring it to your place - I have work through Friday and then a scout camping trip Fri-Sunday morning.
Re: 2017 GLS550 Turbo A Underboost CEL
Set the underboost code again this week. I'd say it's been 5 months since the last one, but it was out of service about 3 weeks due to coolant leak chasing and my lack of availability, and a full month with the deer hit/bumper replacement. So I guess it's only been like 3 months.
With 3 month intervals between setting the code I wonder if I should just let it ride.
With 3 month intervals between setting the code I wonder if I should just let it ride.
Re: 2017 GLS550 Turbo A Underboost CEL
It set the code again so I need to troubleshoot and/or repair. Have any time available tonight or tomorrow since you said some of the diagnosis is probably Benz-tool-specific?
Re: 2017 GLS550 Turbo A Underboost CEL
155k on vehicle.
We checked a few items. From memory:
- Manually ran Xentry test for the boost control system. Passed the tests.
- Manually applied vacuum to each waste gate. After ensuring a good seal at the waste gate nipple, both moved properly and held vacuum
- Tested vacuum harness from the boost control solenoid to the waste gate. No leaks.
- Checked vacuum coming from vacuum pump. Was capable of building 30 inches no issue BUT the needle fluctuated, particularly at lower rpm under increased vacuum demand. Not normal.
- The waste gate rods also fluttered right after engine start which isn't normal either.
Removed the check valve at the outlet of the vacuum pump that routes directly to the boost control solenoid. Check valve fell off and was sitting in the vacuum pump. Verified with borescope and fished out with right angle pick. I was able to rummage through my old parts and found my old check valve that I removed from my E63. That one was still working since I think that vacuum pump was not original, therefore the valve was much newer than the rest of the car. Put that on the GLS550 and bam, no more waste gate flutter.
We did get a code for driver's side air box pressure sensor but it helps when you plug them in....cleared codes, good to go.
This was likely the low boost issue. I would expect improved drivability. I was also thinking more about this. Fluttering waste gates, especially over a longer term, probably prematurely wear out both the linkage, internal flap and even the waste gate diaphragms themselves. It's all very bad.
I do also have my original boost control solenoid if that should prove helpful to a future diagnostic process.
As far as replacement valves, here is an eBay link to the Klifex from Ukraine, like the one I bought. Only $30. https://www.ebay.com/itm/116338088398?_ ... BM3MKDsb1n
If you want to spend a little more but get faster shipping, it now appears to be available on Amazon: https://www.amazon.com/dp/B0BC9RX1QY
Here are some vacuum pump valves and gaskets direct from the Klifex website: https://klifex.com/search/?search=2762300065
I found this later but a video on a new check valve fixing a low boost code on a GLS550....https://youtu.be/sYOrz-8a1Ts?si=WNV8JcIOSBsMm0Dd
Yeah it's a common issue. It's even a 2017.
We checked a few items. From memory:
- Manually ran Xentry test for the boost control system. Passed the tests.
- Manually applied vacuum to each waste gate. After ensuring a good seal at the waste gate nipple, both moved properly and held vacuum
- Tested vacuum harness from the boost control solenoid to the waste gate. No leaks.
- Checked vacuum coming from vacuum pump. Was capable of building 30 inches no issue BUT the needle fluctuated, particularly at lower rpm under increased vacuum demand. Not normal.
- The waste gate rods also fluttered right after engine start which isn't normal either.
Removed the check valve at the outlet of the vacuum pump that routes directly to the boost control solenoid. Check valve fell off and was sitting in the vacuum pump. Verified with borescope and fished out with right angle pick. I was able to rummage through my old parts and found my old check valve that I removed from my E63. That one was still working since I think that vacuum pump was not original, therefore the valve was much newer than the rest of the car. Put that on the GLS550 and bam, no more waste gate flutter.
We did get a code for driver's side air box pressure sensor but it helps when you plug them in....cleared codes, good to go.
This was likely the low boost issue. I would expect improved drivability. I was also thinking more about this. Fluttering waste gates, especially over a longer term, probably prematurely wear out both the linkage, internal flap and even the waste gate diaphragms themselves. It's all very bad.
I do also have my original boost control solenoid if that should prove helpful to a future diagnostic process.
As far as replacement valves, here is an eBay link to the Klifex from Ukraine, like the one I bought. Only $30. https://www.ebay.com/itm/116338088398?_ ... BM3MKDsb1n
If you want to spend a little more but get faster shipping, it now appears to be available on Amazon: https://www.amazon.com/dp/B0BC9RX1QY
Here are some vacuum pump valves and gaskets direct from the Klifex website: https://klifex.com/search/?search=2762300065
I found this later but a video on a new check valve fixing a low boost code on a GLS550....https://youtu.be/sYOrz-8a1Ts?si=WNV8JcIOSBsMm0Dd
Yeah it's a common issue. It's even a 2017.
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