W203/M271 with P0020 fault

[Grasscutter]

Grateful to anyone who can help me with a CEL problem.

The car is a 2004 C180K with M271 engine. For some time the CEL light had been on with a circuit fault for the exhaust camshaft position sensor. Checking the output of the sensor with a 'scope confirmed it was faulty. However, replacing it didn't fix the problem until I finally 'scoped the new sensor to find the output was permanently high. Another new cam sensor has finally sorted that one, but in the meantime I find I've been getting a new error, P0020 "A" Camshaft Position Actuator Circuit.

I've checked the continuity of the wiring of the cam magnets back to the ECU. Unable to fully check the return as these go to "Circuit 87M2e connector sleeve" and I haven't a clue where that is. I was able to verify the returns (pin 2) of both cam magnets are connected together as the circuit diagram shows, so either they're both okay or neither connect back to 'circuit 87M2e connector sleeve'.

I noticed something else while trying to fault find this one. Having had the drivers door open with the engine running, the interior light was changing in intensity, but not as I expected. Bright at idle, dimming slightly as I increased the revs and bright again with the revs at steady state. This led me to measure the battery voltage: 13.7V at idle, 14.2V above idle, dipping to about 13.2V when blipping the throttle. I believe the regulator of the alternator is under engine ECU control. Is it programmed to back off the charge rate if rapid acceleration is called for?

Just for experiment I drove the car briefly with the alternator control wire disconnected. I got P0020 as a pending fault just once rather than bringing on the CEL quickly as it would have done before. Am I looking at a possible alternator fault or is the engine management advanced enough that it won't add another battery drain like the cam magnets if the alternator isn't charging? Alternator has decent brushes and maintains 14.2V at any revs I hold the engine at above idle. Its only moving up from idle or a rapid blip of the throttle that will cause the voltage to momentarily come down.

I have changed out both cam magnets, but the problem's still there. Now am completely stuck. Can anyone help?

Kind regards,

Mike

 

[BlackC55]

Measure the timing chain for stretch.

 

[Grasscutter]

Thanks for the suggestion BlackC55. I've just one other thread on the forum so far and that's about the timing chain. Having read horror stories about chain stretch and my mileage at 120K, coupled with noise from the cam adjusters on start up, I did look at the chain just recently. Timing for the inlet appeared spot on, but the exhaust cam was off slightly. I've got pictures on that thread showing by how much. Was hoping for some advice on that as I didn't understand how the inlet could be okay and the exhaust cam, 3 inches of chain further along, be off. Can wear inside the cam adjusters cause the timing to retard? I hope you're going to say no as I found the cam adjuster sprockets are around £800 a piece from MB!

 

[619]

Hi my name is Chris, I'm from Germany.
My car is a 2002 W203 C180 Kompressor. It also got the M271 motor.

Since two months I have the same problem. My engine light is still burning and a diagnostic tool shows the same error (P0020).

When my car is getting warm, it begans jerking when i stay at a traffic light or in a traffic jam. The car is shaking really bad.

How can I fix this problem?

 

[Grasscutter]

Gone full circle on this one and now solved it. Fitting a new timing chain I think was a worthwhile exercise, but it didn’t fix the P0020 errors. I then started getting the P0365 and P0366 errors again, those relate to circuit and performance of the exhaust camshaft position sensor. Having proved the original and a replacement cam sensor were faulty right at the start of all this and thinking I’d cleared those particular faults when a second new sensor was fitted, I was again in a situation where it looked like the sensor was bad or worse still it was getting wrecked by something. I should point out, the replacement sensors I was fitting were pattern ones at less than a third of the price of the MB OE part.

Refitting the original MB Bosch sensor, I confirmed with an oscilloscope that the output was erratic at idle, but cleaned up when I brought the revs up. Clearing the code with the engine above idle and it stayed clear. Let the engine idle and the fault code came up straight away. The replacement sensor did the opposite, no code at idle, bring the revs up and the code comes with it. This was enough to make me gamble £120 on a genuine MB supplied sensor and it proved to be money well spent. It stopped the PO365 and P0366 errors and no more P0020 error either. (I guess that one was just the engine management being confused by the bad signal from the exhaust cam position sensor).

Sadly it would seem in this case the pattern part just isn’t up to the job and I wish I’d bought the MB part in the first place. It certainly would have saved a lot of messing about, but then I’d probably not have changed the timing chain and found myself in an even bigger mess some time from now. I could also have gone down the route of fitting a new alternator regulator, but now think the way the alternator behaves is normal, so thankful I haven't wasted more dosh there.

To member '619', Chris, I doubt the problem I was seeing is the same as for you. None of the errors for me affected running, performance or fuel consumption.

 

[shorty]

Thanks for the update .
The cel has just come on in my car today , the cars driving fine with no power loss . Im gonna stick it on STAR tomorrow at work to see whats causing the problem . This tread could be very helpful

 

[Alex Crow]

Measure the timing chain for stretch.

#2 for that!

These codes point to imminent major engine surgery if the timing is not checked/chain replaced ASAP.

 

[colifecape]

Hi, I know the feeling. I`m in the middle of taking off my cylinder head to do valve repairs because of a worn chain skipping on the inlet cam. Wish I`d known about theses engines before, i`d defo changed the chain and guides etc.

Coli.

 

[shorty]

I had to change the chain and sprockets on my as well , it has skipped 2 teeth on the intake side , luckly no valves where damaged .

Then less than a week later the head gasket has gone , so the head has to come off anyway

 

[kevkanic]

Hi

I have a problem exactly the same as you guys have been discussing that I just cant seem to get to the bottom of.

We have an E class 2003 1.8 with the 271 engine. I have a returning fault code pointing to exhaust cam position. It does not set at idle, just in the 2-3k rev range normally. We have checked the cam timing and like the pictures posted on here the exhaust cam is fractionaly retarded and the inlet lines up spot on. I dont believe the fault to be a stretched chain as this would also cause the inlet timing to be incorrect.

We have tried swapping the VVC units from cam to cam and it also has new cam magnets (replaced due to oil leaks along with the wiring harness) and we have also replaced the cam postion sensor with a new OE one.

Is there something I am missing here ?

Any help would be greatly appreciated !

 

[Alex Crow]

Hi

I have a problem exactly the same as you guys have been discussing that I just cant seem to get to the bottom of.

We have an E class 2003 1.8 with the 271 engine. I have a returning fault code pointing to exhaust cam position. It does not set at idle, just in the 2-3k rev range normally. We have checked the cam timing and like the pictures posted on here the exhaust cam is fractionaly retarded and the inlet lines up spot on. I dont believe the fault to be a stretched chain as this would also cause the inlet timing to be incorrect.

We have tried swapping the VVC units from cam to cam and it also has new cam magnets (replaced due to oil leaks along with the wiring harness) and we have also replaced the cam postion sensor with a new OE one.

Is there something I am missing here ?

Any help would be greatly appreciated !

Just how retarded is that exhaust cam?

I suspect the exhaust cam has jumped its timing, could it be 1 whole tooth out?

 

[kevkanic]

We have checked and it is not sufficient to be a tooth out !

We have decided to replace the chain anyway now. i will let you know if it cures the fault.

 

[619]

Hi Kev,
do you have good news?

 

[madars.alvikis]

Did you find the problem?

Hi Kev,
do you have good news?

Hi 619.
Did you fix the problem. What was it? I think I have the same issues with my W203 2005 K 1.8 sport

 

[colifecape]

Hi 619.
Did you fix the problem. What was it? I think I have the same issues with my W203 2005 K 1.8 sport

Not a whole tooth out ? I compared chains length when mine went and the overall stretch was around 11 mm. Adds up over the 142 links.

Then again, my tensioner was in bits when I took it out

 

[Socket Set]

Just for the record - mine had jumped 3 teeth on the inlet cam and bent valves very slightly. Chain strech was 11mm over the new one, thats nearly one and a half pitch. The car is 03 with 97,000 and ran perfectly till starting one morning when the tensioner could do no more as the cam tried to push down the valve at cranking speed.These chains need treating like cam belt engines and changing at a whim as there is no prior warning. Nice car Mr Merc. but just shoot the designer of the single chain set up.

 

[walldgreat]

so p0365 gone with replacement of cam sensor magnet?

 

[naghtan]

Gone full circle on this one and now solved it. Fitting a new timing chain I think was a worthwhile exercise, but it didn’t fix the P0020 errors. I then started getting the P0365 and P0366 errors again, those relate to circuit and performance of the exhaust camshaft position sensor. Having proved the original and a replacement cam sensor were faulty right at the start of all this and thinking I’d cleared those particular faults when a second new sensor was fitted, I was again in a situation where it looked like the sensor was bad or worse still it was getting wrecked by something. I should point out, the replacement sensors I was fitting were pattern ones at less than a third of the price of the MB OE part.

Refitting the original MB Bosch sensor, I confirmed with an oscilloscope that the output was erratic at idle, but cleaned up when I brought the revs up. Clearing the code with the engine above idle and it stayed clear. Let the engine idle and the fault code came up straight away. The replacement sensor did the opposite, no code at idle, bring the revs up and the code comes with it. This was enough to make me gamble £120 on a genuine MB supplied sensor and it proved to be money well spent. It stopped the PO365 and P0366 errors and no more P0020 error either. (I guess that one was just the engine management being confused by the bad signal from the exhaust cam position sensor).

Sadly it would seem in this case the pattern part just isn’t up to the job and I wish I’d bought the MB part in the first place. It certainly would have saved a lot of messing about, but then I’d probably not have changed the timing chain and found myself in an even bigger mess some time from now. I could also have gone down the route of fitting a new alternator regulator, but now think the way the alternator behaves is normal, so thankful I haven't wasted more dosh there.

Sorry to bring up these... but I am into similar problem, and it is not so much info about the code P0020.
I am on M272, not exactly yours... but similar... I get P0025 code, related to one solenoid, make the fuel get waste, stop around 15l/100km. Change the solenoid come back nice... now, after serveral months, failure come back, same solenoid, then, change again... and engine come back to 10l/100km, but instant, became code P0020... and I thought it was a Hall position sensor, but it seem, the codes endend at P0019...

Do you think could be about alternator failure? or any other sensor?

Which one you changed? Solenoid A2720510177 or Hall Sensor A2729050043????

Im really a bit desperate...

thanks!

 

[ChrisJJ93]

Soo, after I swapped engine on a wrecked c180 K with a M271.946 engine I bought for around 400 bucks
Car wouldn't start.. faulty code on the knock sensor, exhaust cam posisition value unlikely
Took a compression test just to check after swapping sensors back and forth: very low compression cyl 2 and 3
then checked the timing on the chain; not as it were supposed to be

then timed up the chain again, and to my amazement the chain was not stretched or anything (Compression around 250 kpi on all cyl after) read up that in addition to chain stretch, tensioner giving after there is ALSO; weakness/problems with the variable timing adjusters :'D

Now the car runs smooth, allthough theres a worrying smell; and a lot of white smoke when i run high idle...
so took the obd tester just to check.. no faulty codes.. however I get the CL Fault on fuel system live data :O

this engine is obviously not for people who doesn't work at a workshop or as a car mechanic haha x)
but I do so, will update when the cars perfect!

best regards
- Chris

 

[ChrisJJ93]

*** 250 psi meant to say x)
did change the o2 sensor after the cat and problem fixed, all look good when I do an emission test