MY ALTIMA (2002 4 CYL) SHOWS ON THE SCANER 4*B ON BASE TIMING, THE TIMING CHAIN IS WELL INSTALLED ACCORDING TO THE MARKS, CAN SOMEONE GIVE ME AN ADVICE?

Everything blocking the timing chain cover needs to be removed. THEN REMOVE COVER AND REMOVE OLD CHAIN making sure your cam and crank marks align. install new chain

its use timing chain. and the mark is on the chain just follow the chain

Thomas is right. Due to the expense of repairing the engine, it is usually cheaper to locate a low mileage engine from a salvage yard and have it installed.

2001 , no such ani-mule !
"Introduced for the 2002 model year as a replacement for the Cherokee (XJ),"
you meant manufactures date not model and reg. date. sure.
2002 !
3.7L V6 (cop spark ) chain drive cams....
timing ( cam or spark?)
"Ignition timing is controlled by the Powertrain Control Module (PCM). No adjustment is possible"
so Cam timing (alldata.com covers this in detail)
why not post the context, Im doing what.?
im doing a 60k belt swap
or it slipped. or think id did.
or just put in a new head or cam? see , context is 100% important.
im here, going to there.....
im on line, and it shows 4 engines, i think that is wrong, but...

you must be asking chain cam sprocket timing.
im at alldata.com (or FSM)
there are 37 install steps, im not sure what step you want me
to pluck out. but here is my guess. step 8 ,9,10

1. Install both secondary chains onto the idler sprocket. Align two plated links on the secondary chains to be visible through the two lower openings on the idler sprocket (4 o'clock and 8 o'clock). Once the secondary timing chains are installed, position special tool 8429 to hold chains in place for installation.
2. Align primary chain double plated links with the timing mark at 12 o'clock on the idler sprocket.
3. Align the primary chain single plated link with the timing mark at 6 o'clock on the crankshaft sprocket.

step 12:
Install all chains, crankshaft sprocket, and idler sprocket as an assembly . After guiding both secondary chains through the block and cylinder head openings, affix chains with a elastic strap or equivalent. This will maintain tension on chains to aid in installation. Align the timing mark on the idler sprocket gear to the timing mark on the counterbalance shaft drive gear, then seat idler sprocket fully . Before installing idler sprocket bolt, lubricate washer with oil, and tighten idler sprocket assembly retaining bolt to 25 ft. lbs. (34 Nm).

step 13:

1. Align left camshaft sprocket "L" dot to plated link on chain.
2. Align right camshaft sprocket "R" dot to plated link on chain.

step 15/16

1. Remove Special Tool 8429, then attach both sprockets to camshafts. Remove excess oil from bolts, then Install sprocket bolts, but do not tighten at this time.
2. Verify that all plated links are aligned with the marks on all sprockets and the "V6" marks on camshaft sprockets are at the 12 o'clock position.

do ask questions, or login to alldata.com or mitchels
or get a real FSM.
its nothing trivial.

in fact get the book before the job. so are perpared.

I have the instructions but they are long and will not entirely fit in this forum. [email protected]

After 2002 Altima offers two types of engine: the new 4 cylinder 2.5 L QR model engine which is fairly powerful (175 horsepower) and, I believe, one of the best engine in its class the 3.5L V6 VQ model engine with 240 horsepower. The same V6 model as in in the Nissan Maxima, Pathfinder and Murano.
Both engines feature continuously variable valve timing using a silent chain instead of timing belt. Throttle cable is gone - the throttle operates electronically by wire based on gas pedal sensor readings. This design provides smoother transmission shifting and lower emission.
The 2007 Nissan Altima 3.5L Sedan, has a Timing Chain, and an Ignition Coil Pack. NO DISTRIBUTOR.

Didn't specify what engine but if its the 4 cyl water pump is pulley driven from a belt and is easily seen and changed. If you have the 6 cylinder you will be going into the timing chains as the pump is driven by a chain. Not a do-it-yourself job.

Hello! I have attatched a figure showing proper timing chain and gear orientation. Hope you find this information helpful!

timing belt!!

it will be a belt