Just saw this code yesterday. Car feels low on power even though it's 30F outside although it could just be me. Perhaps I've gotten too used to how the car performs that it doesn't scare me like it used too. Anyway, checked vacuum lines going to both turbo wastegate actuators, and they look OK. Also, no limp mode, CEL, or any of the usual W220 boost or charge-air related codes stored in memory. This P20E2 code is only found under ECM, and no other module. No other DTCs appear related to boost or charge air.

Strange as this code varies depending on which source you check; some say it's a software glitch and to erase the DTC, others claim it's an EGR related code, and others say what my scanner says.

Testing yesterday shows a peak of 1800-1900 mbar or roughly 26 to 27.5 psi at WOT as sensed by the turbo manifold pressure sensors. I didn't get a chance to see at what point the ECU cut boost since I was by myself. Car is still blisteringly fast, but it just didn't feel all there. I was expecting more with outside air temps around 20F. My IATs at the time were averaging 50-55F.

Any thoughts?

Just a guess…boost pressure sensor. It’s probably getting a funky reading or no reading which reads as “too high” as a safety to protect the engine.

http://autoditex.com/page/boost-pres...-bps-24-1.html

I'm not sure where they’re located on this car. Some people think you can clean them. The existence of no other issues in the car leads me away from telling you to check grounds, battery connections, etc., but none of that can hurt. We know these cars act crazy when anything having to do with that hulking battery isn’t perfect.

GL

maw

Well, FWIW I just changed the battery the same day. Removed a dying wet cell lead acid Walmart battery and replaced it with a new 95 Ah AGM (Autocraft Platinum). The old battery had 12.02v across the terminals after about 2 days of sitting. The new fresh battery had right around 12.78v prior to the swap.

Used a 12v OBDII memory saver during the swap with a freshly charged 12v 35 Ah AGM pack. After that was done, fired up the car, checked with my MBII computer, and no data loss. All previous errors still left in memory. All emissions readiness monitors were still initialized and in-tact.

I don't recall ever seeing this code before... and it is a weird code. According to several MB sources, P20E2 just says "Ignore fault code and erase fault memory" or "Software error, memory clear error". Has nothing to do with boost or charge air, as those are completely different codes. Only my MBII comes back with this message.

I don't believe I mentioned it in my original post here, but when I was test driving the car yesterday, I had cleared that code. Floored it a few times to the point that the rear end got real squirrelly. Stopped the car, checked the codes and it was there again. Reset it once more, then drove back to the house. Floored it a few more times (that's when I was able to see the mbar boost readings from the ECU) on the way home. Parked, checked the codes, and no DTC.

So who knows... maybe you're right and the ECU was doing something... maybe adjusting to the new battery? It's going to have to wait though... won't be driving it for the next few months as I just put the car in winter storage and I'm leaving the US for business in a few weeks.

Here's what's from MB specifically:

Didn’t know about the battery. As a stored code, my guess is it won’t be back after the winter. But it is weird….

Oddly enough, it was my 25year old 500E that taught me the importance of battery power to these performance Benzes.

maw

Yeah, the ECUs on these cars are very voltage sensitive. I knew it was time to replace the battery when my external smart charger told me a few weeks ago that the battery was sulfated. My volt meter tests pretty much confirmed.

Anyway, maybe it's placebo effect or something and I've just gotten used to the car. Replaced the engine mounts not too long ago as well, so the ride is smoother. I was thinking to myself that it just didn't feel as brutal as it usually does in 60F weather. Usually with colder, denser air, these things should really come alive. Then I saw that code and thought WTF? But, on the highway, 60 to 120 still happens very quickly, so not sure what to think.

As it is, the car is sitting in my garage with the same smart charger hooked up to the new battery. So by spring time, everything should still be tip top.

Good stuff. It’s been 40s and dry where I am now, and that’s the only reason the 55 isn’t up for the winter. These things just LOVE this weather. Tires don’t hook up as well, but it’s “feathering practice” with the traction control off and the ABC on Sport…

It's almost like working on a computer. Look up an error, and everyone says one thing. Yet, its something else entirely, and a different fix from what everyone says.

Xentry shows 20E2 as "boost pressure too high".

Also, 27psi is high for that car, is the car mapped?

My guess if it is, is that the car is aggressively mapped and overboosted during cold weather (anything above 30psi is past the limit of the map sensors). If it is not mapped, then possibly you have a leak in the wastegate control (from the pass side IC Vac hose which goes to the boost pressure control solenoid.)

Car hasn't been tuned to my knowledge, but it's interesting that Xentry shows that code as an overboost condition when other web resources says it's not related to anything pertaining to boost.

Anyway, cleared the code and drove the car several times since then in similar weather conditions and the code hasn't reappeared.

Quick question, but wouldn't that code in Xentry trigger the dash cluster CEL?

Wouldn't worry about it then, possibly a leaking waste gate line or sticky solenoid valve.

No that code doesn't log an engine light, only puts its in limp mode until throttle restart.