P0476 on the 7.3L Power Stroke Diesel

Using a “VEEPEAK Mini OBDII Diagnostic Scanner” model VP01 and FORSCAN app on my iPAD for code reading and diagnostic tests.

In addition to reading codes, has a list of diagnostic tests.  Including the famous “buzz test”.  That alone makes it worth the price.  Not sure if it’s the app or the hardware flaking out, but lately I’ve been getting an “ELM not detected” error.

FORScan Lite for Ford vehicles

But, before it started flaking out, I ran the “Key On Engine Running On-Demand Self Test” and it threw a P0476 DTC (Diagnostic Trouble Code).  Here’s the service manual blurb:

DTC P0476 indicates an exhaust back pressure control valve performance malfunction was detected during KOER On-Demand Self Test.
Possible causes:
— stuck or damaged turbocharger wastegate valve
— misadjusted or damaged linkage
— restricted exhaust
— exhaust leaks
— damaged PCM
— EPR valve
— EBP sensor

Easiest things first.  I noted a seam on the bottom of the muffler was blown-out over 4″ about a 1/4″ wide, so I patched that up with some muffler cement and furnace tape.  It’ll do for now.  My next assignment is researching mufflers for this beast.  Any input on that is welcome.  I also need to get under the engine cowl and check the up-pipes. I’m sure they need replacing, and that’s my next big job.

Next, I checked the exhaust pressure valve, since there’s no record of that being serviced.  It was as expected; completely clogged with soot.  I mean packed solid.  I started cleaning it out with a little torx head driver and brake cleaner spray, but it was so bad I decided to replace it.  $80 at NAPA. Ouch.

The sensor opening is packed solid with soot. These little guys are easy to damage trying to scrape out the soot. Even the pressurized spray from brake cleaner can damage the internal diaphragm

You can clean the tube in place, but if you do, wrap some tape under the 5/8″ connector fitting up top before you loosen it, otherwise it’ll slide down the tube behind the alternator bracket to the lower manifold connector and you’ll have to pull the tube out to slide it back up.  In order to pull the tube, you need to remove the serpentine belt and pulley.  Actually, it’s a good idea to pull the belt and pulley anyway.  It frees up a lot more room to work.  The only reason not to pull the tube is that it’s kind of tricky feeding it back down behind the bracket.

I found this pic on a 7.3 PSD forum

For the upper connection, it’s tight and you’ll need shorty open end wrenches.  The lower connection at the manifold is tight, but also a long reach.  A long arm 5/8″ open end wrench works best.  It’s a good idea to hit both connections with PB Blaster Penetrating spray well beforehand.  The manifold connection was especially rusty.

Sensor removed, tube detached. Pulley in place, serpentine belt unfitted.

Some folks use speedometer cable or weed-wacker wire to clean the tube. I used an Otis Gun Cleaning cable and some brake cleaner.  Got lots of nasty black gunk out.  In addition to the cable and fluid, I fit a quick release connection to one end and blew it out with 120psi from my compressor.  I’m pretty sure that tube is clean.  I cleaned the bracket nuts with a gun cleaning rod and .22 caliber brush.  Works perfect at the upper location, and for the lower I bent the brush 90° to get into the exhaust manifold opening.

Believe it or not, after the sensor cleaning and replacement, the engine is warming up faster.  I’ve also noticed a marked increase in power and response.  Still more work and diagnostics to do.  Stay tuned!

See You Down the Road!



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