W251 R-Class EGR Issues

[ber5ien]

Disconnected the connector from the ECU and checked the integrity of the circuit.

EGR pin 3 ECU pin 56 - OK beep
EGR pin 5 ECU pin 18 - OK beep

EGR pin 3 ECU pin 18 - no beep
EGR pin 5 ECU pin 56 - no beep

 

[ber5ien]

Thank you very much for all your help, but I give up. I decided to disable it off by the tuner.
I unscrewed all the wiring from the ECU to the EGR.
I'm guessing some other part is causing the problem on that line.
EGR still stuck at 0%.

2 tested EGRs (both OEM), 1 new back pressure sensor, 1 cable to the back pressure sensor, oil leak in vacuum pump fixed (also checked connection to valve to make sure oil is present), checked the EGR valve solenoid (everything is fine, clicks).

STAR does not show any other errors except for the EGR valve and these two codes.

 

[Mersovod]

First I would check the accuracy of all sensors that the ECU uses to control the EGR system.

 

[ber5ien]

Thank you. I will get the readings of these.

• Left hot film air flow sensor (B2/6)
• Intake air temperature sensor (B2/6b1)
• Right hot film air flow sensor (B2/7)
• Intake air temperature sensor (B2/7b1)
• Boost pressure sensor (B5/1)
• Charge air temperature sensor (B17/8)
• Pressure sensor downstream of air filter (B28/5)
• Accelerator pedal sensor (B37)
• Crankshaft Hall sensor (B70)