Recurring P0403 Issue - Diesel Forum -
6.0L Power Stroke Engine and Drivetrain Discussion of the 6.0L Power Stroke diesel engine and drivetrain in the 2003-Up Super Duties and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 6.0L Power Stroke engine.

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post #1 of 4 (permalink) Old 10-30-2017, 07:32 PM Thread Starter
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Recurring P0403 Issue

*I apologize in advance if the narrative is too descriptive. I just wanted folks to have all the information.*

In September I was on a camping trip in Northern Nevada. I took my stock 2006 F-250 SD w/ 90K miles and brand new pair of Interstate batteries on some grated roads as a chase vehicle in case one of the kids decided they were tired and didn't want to ride their motorcycles anymore. We reached our motorcycle destination without an incident and started making our 20 mile trek back to camp when I hit a dip in the dirt road a bit harder than I would have liked. At that point the CEL came on and I scanned it with my Scangauge II, P0403 - EGR circuit malfunction. At this point I did some research and reseated the connection to the EGR valve at the top of the engine. The truck ran fine and the CEL did not come back on the entire trip back to camp.

Two days later we started making our way back to California. After about 30 miles I was coming down a pretty good decent and when I reached the bottom the CEL came on. I scanned it again and the P0403 returned. Since I knew the code now and the suspect part, I opted to go into the closest Ford dealership to get a replacement EGR valve. I stopped to refuel and reset the code and the code returned almost immediately. I stopped for breakfast before the dealership, reset the code. Upon startup and take off towards the dealership the code returned. The dealership was closed but there was a Napa store open and they had the part in stock; Echlin EGR valve for $175. With a mixture of standard and metric tools and assortment of tiny levers I was able to remove and replace the EGR valve. The original valve was black and sooty but nothing out of the ordinary. I ran the truck for about 10 minutes and the CEL did not return. I towed the TT back to Northern California without incident, plenty of power and good mileage.

Since my return home the CEL comes on every now and again with the same P0403 code. I programmed the EGR Voltage code into the SGII and it seems to operate within the documented ranges of 0V-4V. Over the last few months I have gotten pretty good at being able to reproduce the problem on a fairly regular basis. The CEL will not come on so long as the truck has been started cold, left to warm up, and then drive for 10-100 miles. Here's where I can usually get the CEL to come on. If I stop for a bit such as for lunch or go into the grocery store for 10-30 minutes, I can start the truck and take off. If I accelrate such as from a stop sign and then either have to stop suddenly for traffic or the light turns red and I decelerate at a quick rate, the CEL tends to come on with regular frequency. During the deceleration I have witnessed th EGR Voltage go from 0-1 up to 4 and then 0 and CEL comes on. The voltage observations I can not guarantee but I have witnessed that behavior at least twice. FICM voltage is normal during operation at 47.5V~48V.

I'm tempted to get a new Motorcraft EGR valve but I also don't want to spend $250 to just part swap.

Any thoughts and advice are appreciated.
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post #2 of 4 (permalink) Old 10-31-2017, 12:01 PM
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Is the P0403 the ONLY code that comes up?

The typical operating voltage rage for the EGR valve position sensor you should reference is ~0.8V closed. A fully open valve should read ~3.8V maybe closer to 4.0. It should never be 0v or 5v or more. The P0403 means that the PCM has detected an open or short in the control circuits for the EGR valve. That valve sweep you have cited may be the PCM checking the valve and setting the code.

Though I always recommend OEM parts that does not automatically the aftermarket pat you installed is bad and even less of a coincidence would be that you have the EXACT same issue. I suspect a potential harness/connector issue or possibly a bad PCM. P0403 is not a common code.

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post #3 of 4 (permalink) Old 01-11-2019, 05:34 PM Thread Starter
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Thought I would update this thread on final resolution.

I took the truck into the Ford fleet center and they found that the Napa EGR was not operating within spec and replaced with a Motorcraft EGR. After a few days the problem returned. I took it back to the fleet center and after about an hour they were at a loss. I told them to keep the truck and gave them a low budget # to go through the wiring, not to exceed 3 hours of diagnostics. Wouldn't you know they found the wiring problem at hour 2.5. Apparently the aftermarket CAI box is rather large and part of the wiring harness had rubbed enough on one of the edges of the box to begin shorting out one of the wires to the EGR circuit. Technician repaired the wires and the problem has not returned after 1 year of driving.
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post #4 of 4 (permalink) Old 01-17-2019, 01:09 PM
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Thanks for the update!

2006 F250 Lariat Supercrew, ESOF 4x4, 18" tires, FX 4, HD Alt., block heater, Integrated Trailer Brake Controller, Upfitters, power rear window, cab lights - delivered 10/25/05

Ford Remote Start; High idle mod; Timbren load levelers, Scangauge II, Blue Spring upgrade, Quick Start 200 amp large frame alternator, 2 batteries January 2010; GPCM replace October 2011; 2 EGR valves; EGR Cooler replaced 12/30/11; Performance Machine & Mfg. coolant filter added 1/2/12; Rotella T6 5W40 oil; turned rotors, replaced brake pads for 1st time 1/7/12 101K miles; GPCM, both subharnesses and all 8 glowplugs replaced 1/5/13 at 118,000 miles; 2 Ford batteries replaced under battery warranty twice, the latest 9/18/2015; FICM power supply board replaced with Dorman board 11/20/13. Coolant flushed and replaced with Prestone ELC 9/27/14. STC fitting 10/19/14; Dummy Plugs 11/8/14; Turbo rebuilt 11/29/14; cold side CAC tube and boots replaced with metal tube 1/24/15; replaced hot side boots 1/30/16.
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