TECH TIP
2004 MERCEDES NO CRANK ISSUE
Nov. 12 2019
Nov. 12 2019

Vehicle: 2004 Mercedes Benz SL 500 (230.475), V8-5.0L (113.963), Automatic Transmission

Mileage: 198,009

Problem: The engine fails to crank over when the ignition is switched to the START position.

Details: The first thing the technician did was to connect a scan tool. He retrieved a B1829 (Starter battery circuit component error) diagnostic trouble code (DTC).

Next, he pulled the starter relay (see image for location) out of the fuse box and measured voltage between relay socket terminals 85 and 86 (control coil) while the ignition was in the crank position.

Mercedes Starter Relay

There was battery voltage at terminals 85 and 86, and on terminal 30. He connected a fused jumper wire to bridge terminal 30 to terminal 87. The starter engaged so he deduced that the relay was faulty.

Confirmed Repair: The technician replaced the starter relay and cleared the DTC. The new relay restored normal cranking, the engine started, and no code returned. Problem solved!

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