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Ford expert
Ford expert, ASE Certified Technician
Category: Ford
Satisfied Customers: 10370
Experience:  30 yrs,experience shop owner,
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2004 f150 will not start when it gets wet?

Resolved Question:

2004 f150 will not start when it gets wet?
Submitted: 5 years ago.
Category: Ford
Expert:  Ford expert replied 5 years ago.
Welcome to just I'm here to help you and your 100% satisfaction is my goal. This can be caused by a number of things but very commonly you'll find water damage were water is leaking down from the windshield into the gem module and the inside fuse box or otherwise known as a central junction box,Check fuse #102 20A in the interior fuse panel first. Verify the fuse is in
place and has battery voltage on both sides. Replace the fuse as needed. If the fuse is OK, access the ignition switch. Check the Light
Green/Violet wire for battery voltage at pin 4 from fuse #102. If
battery voltage is not present, repair the circuit between the interior fuse
panel and ignition switch. If battery voltage is present on the LG/VT
wire, leaving the ignition switch connected and in the RUN position, check for
battery voltage out of the ignition switch on the Dark Blue/Light Green
wire at pin 1, Black/Light Green wire at pin 6, and the Red/Light Green
wire at pin 7. If there is no voltage out on any of the wires, verify
the connections are OK. If the connections are good, suspect a faulty ignition
Customer: replied 5 years ago.

will not start when it gets wet under the truck. hand wash it's ok. take it in a car wash with a chassis wash, the truck will shut off. normal rain fall it's ok. flooded roads it will shut off. i'm thinking something on the bottom of the truck

Expert:  Ford expert replied 5 years ago.
i'm thinking crank sensor or sensor wiring When cranking the engine over, observe the check engine light. It should be on
Key On Engine Off but go out when cranking the engine. Cranking RPM can
also be monitored on scan tool data. If the light remains on when
cranking, this indicates that the Powertrain Control Module is not
receiving a Crankshaft Position Sensor signal. Disconnect the
CKP sensor and install an AC voltmeter between the 2 pins at the sensor. Crank the engine over and look for AC voltage output, typically
between .7 - 1.2 volts. If the sensor does not output any voltage,
replace the CKP sensor and retest. If the sensor does output good
voltage, check the Dark Blue wire and the Gray wire from the CKP to
pins 47 and 46 of C175e of the PCM for opens or shorts and service as
Customer: replied 5 years ago.
that idea did not work
Expert:  Ford expert replied 5 years ago.
Customer: replied 5 years ago.
5.4 3v
Expert:  Ford expert replied 5 years ago.
Check fuse #32 15, #33 15A, and #34 20A in the Central Junction Box
interior fuse panel with key on for full battery voltage from the Powertrain
Control Module PCM power relay. If none of the fuses have battery
voltage as they should, check fuse #28 5A for battery voltage with key on.
This fuse feeds the PCM power relay to turn it on with the key. If
fuse #28 is OK, remove the PCM power relay relay #203 and verify that there
are two terminals with full battery voltage with key on- one from fuse #28, the
other should be battery voltage at all times and is hard wired to the battery
voltage input to the CJB. If both terminals have battery voltage as they should,
swap the PCM power relay with either the Trailer Tow Parking Lamp Relay #201,
or the Fog Lamp Relay #202 and recheck operation. If fuses 32, 33, and 34 now
have battery voltage, verify the vehicle starts and runs and replace the PCM
power relay as needed.
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