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Water Damage

You drove through a flooded street: don't hook up the battery to test it

31 Aug 20266 min read

Connecting the battery after driving through a flooded street is the mistake that turns a roughly $500 preventive rescue into a dealer invoice over $4,500. The dealership calls it a total loss of the electrical system and demands a new engine computer, a new body module and a full harness. What matters here is that the flood didn't cause that jump in price: the attempt to start it afterward did.

Symptom bench

The drying illusion, step by step

Pick the symptom to see the likely cause

01 / 05

The carpets feel dry after two days in the sun

The water evaporated, but that says nothing about what it left behind inside the modules.

What the water leaves when it goes

Rainwater in Florida isn't pure: it carries asphalt residue, pollen and mineral salts. Under the sun the water disappears but the minerals crystallize into a highly conductive crust, lodged in the blind spaces under the BGA microprocessor — which is exactly where nobody looks and nothing dries.

On a modern platform like the 2019 Sprinter, engine management depends on a Bosch MD1CP001 run by an Infineon TriCore Aurix in a BGA package, with tight voltage tolerances. When you connect the battery, the module immediately receives an unswitched 12 volts on the +30 line. The mineral crust acts as a very low resistance bridge and those 12V cross straight into the 3.3V and 1.2V reference traces feeding the logic core. The fuse takes milliseconds to react; the silicon takes microseconds to perforate.

Test bench

Where the current crosses over

> critical module: bosch md1cp001, multilayer engine computer
> central processor: infineon tricore aurix, BGA package
✔ normal voltages: 1.2V logic core, 3.3V and 5.0V sensors, 12.6V power
⚠ mineral bridge: 12V from the +30 line reaches the 1.2V traces
⚠ mechanism: cross dielectric breakdown, irreversible
Codes read

If the processor half survives

P0606 — ECM/PCM Processor Fault: physical damage in the logic gates
U0100 — Lost Communication with ECM/PCM "A": CAN transceiver collapse
P068A — ECM/PCM Power Relay De-Energized: thermal protection cut
> if no code appears at all, the module no longer answers on the network

If your vehicle went through water, there's one rule: don't energize the chassis. Disconnect the battery immediately and don't turn the key to test it. Everything that can be saved gets saved before voltage is applied; after the snap, there's nothing left to clean.

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How a wet computer gets rescued

  1. Step 01

    Cold triage

    We remove the aluminum housing in an ESD environment and measure impedance on the main rails with a bench meter, looking for passive shorts before powering anything.

  2. Step 02

    Ultrasonic chemical cavitation at 40 kHz

    We submerge the board in non-alkaline dielectric solvents; the waves implode against the circuit and strip the salts and copper oxide hidden beneath the BGA processors.

  3. Step 03

    Structural dehydration

    We bake the module at 140 °F in a vacuum convection chamber to pull moisture trapped between the eight internal PCB layers.

  4. Step 04

    Bench regulation check

    We validate the Zener diodes and internal regulators, and power the unit from lab supplies with tight current limiting so the processor boots safely.

  5. Step 05

    Sealing and delivery

    The unit is closed to military spec against moisture and comes back ready to plug in.

Because we rescue your original hardware, the EEPROM holding the security algorithm — FBS4 on Mercedes-Benz, PATS on Ford — the VIN and the injector coding all stay intact. The vehicle starts with no tow to the dealership and no online programming sessions.

Did your car go through water? Write to us before you connect the battery, not after.

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