W251 R-Class EGR Issues

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  • Thread starterber5ien
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ber5ien
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I have constant problems with the EGR system. The car goes into limp mode. In winter everything was fine. In hot weather for some reason everything gets worse.

Replaced the back pressure sensor with a new one (OEM Mercedes).
Replaced cable to back pressure sensor (OEM Mercedes).
Replaced the EGR with an aftermarket one (no changes), installed the original back in (Mercedes OEM).
The mechanic checked the EGR, it opens/closes.
There were cracks in the rubber of the EGR pressure valve. This was fixed, but I probably did it myself during troubleshooting.
Checked the intake system with smoke (no problems, no leaks, all seals/gaskets are OK).

The car is a Mercedes R-Class 2011 OM642 350 CDI 263.

I suspect the cable that connects to the EGR is damaged, but I don't have any diagrams and I'm not sure what exactly to check.
Any ideas would be great.
 
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Does this sound like an electronic problem?
 
Check the chrome tube at the front of the engine for blockages and also check the EGR entry point into the intake manifold for positive deflection.
You also have an electrical fault with the EGR valve. Please provide your VIN so we can send you a circuit diagram.
 
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I cleaned both of these pipes and the connector.
There was a hole in the rubber tee and that was replaced too.
 
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At this moment I would like to check this 5-pin connector connection.
 
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I had the same problem, I can recommend removing EGR.
 
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I asked two tuners, both said it could be something else. Funny. Just want to fix it. Thanks for the info.
Did you use someone else's services or do it yourself?
What was the cost?
 
Here is the electrical circuit diagram if that helps.
 
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Here is the wiring diagram for the CDI unit that includes the EGR positioner Y27/9 with a 5-pin connector (page 6).
 
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You are right to focus on the 5-pin connector.
First, make sure none of the pins are damaged.
Then check if there is reference voltage between contacts 3 and 4 (this should be fine as it also powers the crankshaft sensor and others).
Finally, check the continuity to the CDI module N3/9 (pin 3 connects to pin 56 of N3/9, pin 5 to pin 18, pin 2 to pin 72 and pin 1 to pin 96).

I think pins 1 and 2 are negative and positive for the valve motor. Pin 5 is the valve position signal. Pins 3 and 4 are for reference voltage and are common to other sensors.
 

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