These suggestions and solutions for technical problems come from service bulletins and other technical information published by Mercedes-Benz, selected and rewritten for independent repair shops.

Rear Axle Noise

Model 199.376,

VIN 000018 to 000897

A grinding noise from the rear axle on these vehicles may be caused by inadequate clearance between the rear brakes and the backing plate. Check the clearance. If there is less than 0.4 mm space at any point between the brake disc and backing plate, the backing plate must be replaced.

Rough Idle, Code

P201A/B,

Model 203.040/740, with Engine No. Up To 271

###-30-677695

Rough idle, which may also set a Fault Code P201A/B, can be caused by carbon build-up on the exhaust valve stems, exhaust valve guide wear, or leaking valve seats.

1. Check for the fault code P201A/B (cylinder misfire).
2. Remove spark plugs and do a boroscope inspection of all cylinders. Turn the crank shaft until the exhaust valves are fully extended so that the valve stems and valve seats can be evaluated.
3. If the valve stems are only lightly covered with carbon, continue with steps 6 through 8.
4. If the valve stems are heavily covered with carbon, continue with steps 9 through 11.
5. If the exhaust valve seat(s) are worn, continue with steps 12 and 13.
6. Install spark plugs.
7. Free up the engine by revving the engine to approximately 4,000 rpm and hold at this engine speed for at least 10 minutes.
8. Update the engine control unit and perform SCN coding. Note: Use latest DAS release.
9. Using an air holder, remove/install/replace all exhaust valve springs with part numbers indicated in parts table. The exhaust valves do not have to be replaced.
10. Install spark plugs.
11. Update engine control unit and perform SCN coding.
12. Perform cylinder compression leakage test and compare the values of the individual cylinders.
13. If the exhaust valve seats are leaking and the loss between cylinders is greater than 20%, replace the cylinder head.

Power Outlet Failure

Model 203.052, VIN E019387-E021112

If the power outlet (cigarette lighter) doesn’t work, check for a missing relay in slot “F” and/or a missing 15A fuse in slot “12” of the Rear Signal Acquisition and Actuation Module (SAM). Install a new relay and/or fuse if either part is missing.