Computer codes check engine light on, codes PO358 and PO403?

Tiny
NICK73
  • MEMBER
  • 2003 MERCURY MOUNTAINEER
  • 4.6L
  • V8
  • 4WD
  • AUTOMATIC
  • 154,550 MILES
Two codes came up; PO358 and PO403.
Sunday, April 2nd, 2023 AT 2:17 PM

1 Reply

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,724 POSTS
Hi,

Did both of these show up at the same time? I ask because the P0358 is related to an ignition coil issue. Are you feeling a misfire or does the vehicle seem to have lost power?

The P0403 is related to the EGR valve (exhaust gas recirculation).

Do me a favor. The EGR valve is mounted to the side of the intake manifold. (See pic 1 below).

I highlighted the component and have an arrow pointing to where there should be a vacuum hose. Make sure that it is good and there are no leaks present. If it appears good, check where it mounts (circled in red) and make sure there is no evidence of a leak at that point.

Let me know what you find.

Joe

See pic below.
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Sunday, April 2nd, 2023 AT 9:49 PM

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