What is the ecu-b fuse for on a 2004 tundra 4wd 4.7

Did you let the vehicle sit for 30 min. before testing ? Modules need to time out (go to sleep - power down etc.. How are you testing ? Have a ammeter inline with battery negative cable and negative battery post . Have any doors open ( door switch closed ) Key out of ignition ? How much current ? 50 milliamps max !

Thread: 4 Wheel Drive just broke - Tundra Solutions

www.tundrasolutions.com/...driveshaft.../1419-4-wheel-drive-just-broke/
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Any Tundra owners had the blinking orange light 4WD problem

Four wheel drive actuator may me at fault, try park the truck on a slick surface like wet grass, set it in neutral and activate 4hi and 4lo back to 2wd a few times, if doesn't help try tapping on motor actuator located on transfer case while someone activates selector, park surface must be as level as possible, a good tip is to activate your four wheel drive once every few months to avoid it freezing up.If nothing helps then it needs to be diagnos by a tech. good luck

Have you checked the gear position sensor? That would be my first place to start.

PT 4wd, or AWD?

the car if PT 4wd must not be driving on dry pavement.
only dirt, ice or snow. the reason its called Part time is that fact.
so if PT, and you are on say ice, and the lamp is out.
then the leaver is not working, the lamp does not prove 4wd.
it only proves 1 gear moved to 4wd in the transfer case.
read the FSM on you car, it has all these test.

move car to dirt. grass or ice and try one more time
is the lamp on now, good.
if lamp is on now test 4wd now, id it working for real?

for 4wd Pt to work the XFR cases need to be in 4wd
and power leaving case to front axles.
and the front axle must lock up. the fsm has the test for each step.
RTM.

alldata.com might help, login and read the 4wd sections.

you probably have a vacume leak , there is a control harness that runs from the front axle up on the transmisson , usually with 4 little hoses attached and it plugs in at the transmission, that is where the vacume comes from , that is where I would start

4 wheel drive does not engage on a 2004 toyota tundra

Does the 4wd icon on the dash blink when you try? The most common problem I have seen is the 4wd actuator sticking. Its mounted towards the rear of the transfer case on the drivers side(US). It has about a 3inch electrical plug on it. Locate it and with the truck running have someone push the 4wd button while you lightly tap on the actuator motor. They can sometimes stick from lack of use. If it doesn't free up it may need to be replaced which is rather involved. The transfer case would need to be removed and opened up to replace.
Good luck.

Its possible the 4wd actuator on the transfer case is sticking from lack of use. Its a black plastic part located on your transfer case on the drivers side rear with a electrical connector attached. Tap on it lightly while someone activates the 4wd button. Have truck running in neutral with foot on brake. (dont get run over). If it goes into 4wd, then just remember to cycle it into 4wd and back again once or twice a month to keep it from sticking.
If all this doesn't work a dealer will need to look at it.