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&quot ; UH OH&
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Discussion Starter #1
It is very cold here in Kentucky so maybe the weather is causing this problem. I have a 03 6.0 powerstroke f-250 and the 4xlow will not engage nor will the light on the dash illuminate. The 4xhigh engages and illuminates on the dash just fine.
The 4xlow worked fine in the field saturday. Does the 4x low have a fuse somewhere? Can anyone help me with some diagnostics here?.........Tom
 

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There is not a dedicated fuse for low range functions, but you could always check all the fuses associated with the elec shift functions. they are all in the fuse box inside under the dash. You can check the fuses with a test light

Fuse numbers 31-(hot in start), 33-(hot in run/acc), 34-(hot all the time), 45-(hot in start/run).

Most electronic shift failures usually cause the associated indicator light to flash but not always.

What I have seen on a few trucks was a concern with the brake lamp switch. This is the same switch but not the same circuit that operates the brake lamps and is mounted on the brake pedal bracket, the switch is a dual contact switch. If you had a test light you can check the brake lamp switch for proper operation.

With test light, verify that the LB/BK (lt blue/black) wire is hot, next check the RD/LG (red/lt green) wire get power when you press the brake pedal down.

I know you probably already know this but,
FYI... For Low Range: the four-wheel drive (4WD) control module requires that the vehicle speed be less than 3 mph, the brake pedal be applied, and the transmission in NEUTRAL (automatic transmission) or the clutch pedal be depressed (manual transmission).
 
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