MERCEDES-BENZ CLK (C209) |
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Unstable idling. The vehicle displays the following faults codes: 3698, 3699, 0745 – P0171 and/or 0749. |
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SYMPTOMS:
CAUSE/S:
3698 – Fuel pressure, regulation. The lower limit has been reached, the rail pressure sensor has malfunctions.
3699 – Fuel pressure, regulation. The upper limit has been reached, the rail pressure sensor has malfunctions.
0745 – P0171 – Self-adjustment of mixture formation for enriching at idle for the right-hand cylinder bank is above the permissible limit.
0749 – Self-adjustment of mixture formation for enriching at idle for the left-hand cylinder bank is above the permissible limit.
Fault codes recorded in the engine control unit.
The vehicle displays one or several of the above-mentioned fault codes.
Engine warning light (MIL) ON.
Unstable idling.
NOTE: Fault codes 3698 and 3699 are displayed together with fault codes 0745 or 0749.
Possible causes:
• Defects in the engine sealing.
• Defects in the sealing of the intake air manifold assembly.
SOLUTION
Repair procedure:
• Read the fault codes recorded in the engine control unit using the diagnostic tool.
• Confirm that one or several of the fault codes that appear in the field symptoms of this bulletin are displayed.
• Confirm that the symptoms mentioned in the field symptoms of this bulletin are reproduced.
• Check if there is an additional air intake, with the engine running, spray a brake cleaner or a similar product on the parts which are especially susceptible to have an additional air intake and observe the lambda values or by using a low-pressure loss detector that generates smoke and a contrast agent. Repair the air intake if necessary.
Carry out the following checks if the defect has not been detected using the above-mentioned means:
• Check if the engine oil dipstick seats properly in the upper part of the guide tube.
• Check if the O-rings of the oil dipstick are not damaged. Replace the seals if necessary.
• Check if the guide tube of the oil dipstick in the oil pan is damaged or if it seats properly on its base. Replace the guide tube if necessary.
• Check if the vacuum connection for the air shutoff valve is installed correctly. Install and fasten the connection properly (See image 1-A).
• Check the O-ring of the vacuum hose connection with the brake servo. Replace the O-ring if necessary (See image 1-B).
• Check if the vacuum line at the connection piece for the intake pipe switching is fastened properly or if it does not seat correctly. Place or seat properly the line if necessary (See image 1-C).
• Check the seal between the intake manifold assembly and the engine. Replace the seal if necessary (See image 1-D).
• Check the seal between the upper and lower part of the intake manifold. Replace the seal if necessary (See image 1-E).
• Check if the seal between the air filter housing and the intake manifold is installed correctly or if it is damaged. Reposition correctly or replace the seal if necessary (See image 1-F).
• Check if the canister line is positioned properly. Reposition the line if necessary (See image 1-G).
• Check the leakage at the axle guide for the intake manifold switchover. Repair the leakage if necessary (See image 1-H).
• Check the circuit leakage and the vent lines of the engine ventilation. Repair the leakage or replace the lines if necessary (See image 2-A).
For model 164.177 up to VIN xA 185373, perform the following procedure:
• Check if the diameter of the fuel feed line to rail at the height of the metal weave is 13.6 mm. In case the diameter of the installed line is 11.0 mm, replace the fuel line with one with a larger diameter.
NOTE: It is recommended to replace the aluminum bolts of the intake manifold in case of disassembly.
IMAGE 1:
A – Vacuum fitting for shut-off valves.
B – O-ring of the vacuum hose connection.
C – Vacuum hose in the fastening part for the intake pipe switchover.
D – Sealing gasket between the intake manifold assembly and the engine.
E – Gasket between the top and bottom of the intake manifold.
F – Gasket between air cleaner housing and intake manifold.
G – Canister line.
H – Axle guide for intake manifold switchover.

IMAGE 2:
A – Engine ventilation circuit.

MERCEDES-BENZ CLK (C209) |
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Ralentí inestable. Vehículo presenta los siguientes códigos de avería: 3698, 3699, 0745 – P0171 y/o 0749 |
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MERCEDES-BENZ CLK (C209) |
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Ralenti instável. O veículo tem o seguintes códigos de falha: 3698, 3699, 0745 – P0171 e/ou 0749. |
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MERCEDES-BENZ CLK (C209) |
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Le ralenti est instable. Le véhicule présente les codes défauts suivants : 3698, 3699, 0745 – P0171 et/ou 0749. |
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MERCEDES-BENZ CLK (C209) |
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Instabiel stationair. Het voertuig registreert de volgende foutcodes: 3698, 3699, 0745 – P0171 en/of 0749. |
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