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2011 W221 S350 Bluetech experiencing intermittent non-start problem.


Grundysp

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To whoever it may concern,

I have been experiencing a persistent problem with my automobile for three years and have made some observations that might assist an expert in diagnosing the issue. Simply put, sometimes the automobile fails to start and does not even make a cranking noise when the key is turned all the way to the right.

Vehicle: Mercedes-Benz S350 Bluetech, 2011 model (W221)

Side note: When the automobile starts successfully (although occasionally after a delay, either on the first or second attempt), all problems vanish, and it operates smoothly as expected.

Symptoms: - Ignition key moved to the second position, but engine does not start, no cranking sound.
Two problems appear on the dashboard. Run-flat system malfunction, Electronic Stability Programme malfunction
The engine coolant temperature gauge remains static on the dashboard, regardless of the car's prior operation and expected temperature range of 60-80°C. The pre-ignition glow indicator does not illuminate even when the engine is cold. The compressor for the air suspension does not produce the expected hissing sound, indicating it is not functioning. The system is displaying two pending error codes. Error codes P0113 and P00AD indicate issues with Intake Air Temperature Sensor 1.

I have deduced that the issue is likely related to the battery voltage, since it consistently occurs during winter and cold weather. I have not seen it during the summer season. It seldom happens after the vehicle has been driven and warmed up. Keep in mind that voltage increases over a long period of use, indicating a greater level of battery charge.
When my battery voltage dropped below 12V, it took me an hour to start the vehicle by repeatedly twisting the key and hoping for it to start. When I replaced the battery with a fully charged one, an error may occur. However, after attempting to start the engine 2-3 times, I am able to switch it on. On another occasion, I attempted to jump-start the car from another running vehicle after 20 minutes of unsuccessful attempts to start it on its own. The car began promptly and no error was shown.

Despite having a new, fully charged 95Ah AGM batteries, I still have this message and sporadic starting problem.

Additionally, when the key is turned to position 2, several customers are activated. The air suspension compressor would initiate, pre-ignition glow, and air conditioning air, among other functions. Before attempting to start the engine, I see that the battery voltage decreases by around 0.5 volts. After fully charging a new battery, it reads 12.5V initially, but drops to 12.0V after turning the key twice. Occasionally, when turning the key to position 2, the glow plug briefly appears and the air suspension starts hissing, but then abruptly stops, displaying an error message on the dashboard and preventing the car from starting.

Could this issue be a short-circuit triggered by a component activated while the ignition is in position 2? When voltage decreases, some modules may fail, resulting in errors or the vehicle not starting. It is peculiar that the vehicle consistently starts, but it may sometimes need up to an hour, or locking the doors after an unsuccessful attempt and attempting again 20 minutes later.

Value accurate estimations.

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Can water cause damage to an ECU? Blocked drains at the windscreen base might cause water to pour into the battery compartment, potentially damaging the neighbouring ECU.

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Thank you, that may be the issue since the drains were plugged some time ago. The problem occurred at least twice with a heated engine when the automobile was exposed to water: once after washing the car with a jet wash and once after a lengthy drive in the rain.

It's frustrating because none of the garages, even Mercedes-Benz ones, inspect or clean the drains. I had to accept that I need to undertake this task on my own.

If the ECU is broken, will increasing the voltage still assist in starting the vehicle and resolving the errors? This morning, when I attempted to start the automobile, the same problems appeared. I used another battery, a 3-year-old authentic MB battery that I had just replaced with a brand new one, to lift the vehicle up. This action caused all errors to vanish, and the car started immediately.

Is my battery voltage within the standard range? A new 95Ah AGM Varta battery, with a slightly larger capacity than the original Mercedes-Benz battery, was fitted fully charged at 12.7V. After driving for 3 hours on the highway, the following morning the battery voltage was only displaying 12.2-12.3V. When I turn the key twice to start all consumers (air compression, pre-ignition light stuff), the voltage lowers by 0.5V to below 12V right before I start turning up the engine.

I would much appreciate any advice for a reputable independent garage in London

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The battery voltage should be around 14 volts while the engine is operating. If it is not, then the battery is not being charged.

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A voltage reduction on a fresh battery the following morning after a 3-hour run is unexpected. Consider testing for a parasitic current draw using an amp metre. Be cautious while doing so. Vehicles may take some time to completely shut down. Ideally, there should be no more than a 30mA draw when the vehicle is totally shut down.

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