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Hi, my name is***** you a technician? Do you have a Mercedes scan tool?
Yes the relay powers the purple wire. Have you replaced the relay yet?
You can test for power to the relay by removing the relay and putting your voltmeter between terminal 85 and 86 in the relay box then turning the key and checking for 12V when the key is turned to the start position.
Are you still with me?
Your test is done with the key in the start position NOT in the run position.
The starter relay is the green relay in the passenger side fuse and relay box under the hood.
If you aren't getting 12V to the relay in the start position try disconnecting the electrical connector at the front of the transmission and see if it will start.
I have schematics but I cannot post them here. I can send them to your private email for an additional service fee. Did you try disconnecting the electrical connector at the transmission then try starting the car?
The starter relay is part number 002 542 76 19. As long as you purchased the correct part number it shouldn't make any difference. The usual problem on this model when you have no power to the starter is either a bad electrics plate in the transmission or a bad gearshift assembly or a bad transmission control unit. Basically the ECU does not get the message that the car is in park therefore it will not engage the starter.
Yes it should start in park or in neutral. When turning the key to the start position you should have 12V across 85 and 86.