How to replace a egr valve on a 2003 linclon navigator?

Lincoln nav.
well is the engine the same size ?
it sold new with 1 of 3 engines
4.6 and 5.4, 2v and 4v. 4v is DOHC twincam head
so is 3 unique engines there, day 1. new.
so of both cars have same engine ,
and the parts counter told me it is same on 5.4L
so did rockauto.com,
if still OEM stock that is, some 3rd party sold parts might say different.
vast those.

7.5 amp. Check this page out or your owner's manual for the fuse diagram: https://fuse-box.info/lincoln/lincoln-navigator-2003-2006-fuses-and-relay

Betty, Check the attached EGR links,instruction and guides, Good luck
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This is a problem in the EGR or EGR control solemoid. It is indicating the EGR valve is not in the proper position. It can be a stuck egr valve or lack of proper Egr vacuum pressure to position the valve.

Remove the air cleaner outlet tube. Detach the EGR tube (Fig. 1). Disconnect the EGR vacuum tube. Remove the EGR valve (Fig. 2). Remove and discard the EGR valve gasket. To aid instillation, loosen the EGR tube bolts at the exhaust manifold. Install a new EGR valve and gasket.

Hi thanks for your question' The electronic EGR valve and solenoid assembly is attached to the rear of the left cylinder head ,

1. Remove electrical connector (5) at top of EGR valve solenoid.
2. Remove tube mounting bolt (1) at intake manifold.

1. Remove two bolts (4) connecting EGR tube (1) to valve assembly.
2. Remove gasket located between EGR tube flange and EGR valve assembly.
3. Remove two EGR valve mounting bolts (5).
4. Separate valve assembly (3) from engine.
5. Remove and discard metal gasket located between cylinder head and valve assembly.

INSTALLATION

1. Clean area at rear of left cylinder head where it joins base of EGR valve.
2. Clean EGR tube where it joins EGR valve.
3. Position new gasket between EGR valve and cylinder head.
4. Position EGR valve to cylinder head. Install and tighten two bolts (5). Refer to Torque Specifications.
5. Position new gasket between EGR tube flange and EGR valve assembly.
6. Position EGR tube (1) to side of EGR valve and into intake manifold.
   1. Install EGR tube flange bolt (1) at intake manifold. Tighten bolt. Refer to Torque Specifications.
   2. Connect electrical connector (5) to top of EGR valve solenoid (2).Do a final tightening of two EGR tube bolts (4). Refer to Torque Specifications

you did not post what model of Linclon, but in any case the PO 0171 is fuel system to lean on bank 1.

look for a vacuum leak if no leak then you will need to test the fuel system, there are many idems that could set this code ( injector, vacuum leak, EGR valve, TPS sensor, ect.....) there is a test for the code but you will need to have a scanner to run the test, A SCANNER NOT A CODE READER. if you would like the test i will send it to you but it is many pages.

are you sure its bad? i've never had a bad one.

You may have to reset the error memory of the on board computer via a brand and model specific procedure. Some errors may be erased simply by turning the ignition on and off a particular number of times.

Check your codes, you might get an EGR code, Fords are notorius for bad breathing,
clean your throttle body also