WILL NOT START

HI/LO Freon switch is first or relay stays off line 5.7L V8 GAS OR DIESEL? 2 ARE DIESEL OF 3.
scan the PCM first. p0646?

THE PCM CUTS THE CLUTCH FOR MANY REASONS;
HI/LO SWITCH TRIPPED
CAB BLOWER DEAD
ENGINE OVERHEAT (OR SENSOR FOR THAT TELLING A BIG LIE)
ENGINE OVER LOADED RUNNING WOT.
EVAP CAR ICE UP SENSOR. TRIPPED.
FUSES.
NO SCANNING PCM WE MISS THE BOAT .
WAY TOO COLD OUTSIDE, SENSED.
ENGINE RAD FANS DETECTED DEAD.
CLUTCH IS BAD OR SHORT OR OPEN COIL
RELAY BAD.
THE NEW RELAY SHOWS 5 PINS. SO IS BIG CLUE THERE.
CAB FUSE BOX NOT ENGINE BAY
LEFT SIDE COLUMN OF RELAYS
TO9 LEFT SPARE RELAY,FOG, ASD ,CLUTCH
4 DOWN LEFT

Check the harness bulkhead connector at the firewall. If you have been driving in deep water, you will get corrosion here. This connector is where power enters the cab (kickpanel fuse block). Use conductive grease at connector after cleaning the pins

lower dash drivers side , cover/lid will give list of fuses etc, also fuse box in the engine compertment near to the battery

its not a relay problem if the starter is clicking it is a resistance problem check voltage on the big supply wire and on the small signal wire if either is lower than battery voltage start moving back on wire untill battery voltage is present, repair as necessary

have you checked the glow plugs

Fuse #2 in the fuse box behind the driver's knee panel is the 5amp "KAM" fuse. The others,in under the hood fuse box would not be a concern as without them being good the engine will not start and no code read would be possible.

I would start with having the starter checked and the wiring leading to it, if it is in fact not turning over a t all

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Relays will click when they're getting power to initiate them. They may not be getting power from their main source. Check under hood for a set of fusible links, if all your small fuses in fuse box are good.

check the large relay in the fuse box and push it down it works a number things