P1378 code ?? - Ford Powerstroke Diesel Forum
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post #1 of 2 Old 07-05-2012, 03:42 PM Thread Starter
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P1378 code ??

Just noticed today according to my gryphon ficm tuner I'm getting the p1378 code which means low voltage to ficm. I checked my ficm output and am getting no less than 48 volts even when cranking. My ficm input was reading 11-12.5 volts. Does the input seem normal ? The truck runs starts idles great. I'm getting great fuel mileage aswell no blue or white smoke. Just curious as to what's causing that code to keep popping up after I clear it.

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post #2 of 2 Old 06-20-2016, 03:48 PM
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I realize this post is nearly 4 years old, but I have the same issue.

Truck starts, idles and runs great. I recently decided to try and get to the bottom of my P1378 DTC that keeps rearing its ugly head. I went as far as replacing my batteries (previous ones were ~ 4 years old, but still worked great). I also replaced the FICM relay (F8OZ-14N089-AA).... but the P1378 keeps coming back.

AutoEnginuity reports my FICM Logic Power never drops below 10V... even then, the lowest voltage reading is during cranking with the glow-plugs still on and only for a fraction of a second. The always truck starts within 1 or 1.5 seconds of cranking, and FICM Logic Voltage jumps up to 11.5V-12V right away. FICM Main Power stays steady at 48V at all times...

The FICM Tech Guide (https://swampsdiesel.com/files/Fordficm.pdf) seems to indicate that P1378 is only triggered when FICM Logic Power drops to less than 7 volts. This is not happening on my truck... or at least AE doesn't see it.

Only thing on the PCM out of the ordinary is a Edge Platinum Juice with Attitude module. Not sure if this could be a factor.

I apologize in advance if this has already been explored and answered...

Thanks guys!

vitamin joe

2004 Ford F-350 Lariat FX4 4x4 SRW
301686 km (187459 miles) as of August 8, 2016
15.20 avg mpg

Delo ELC - CAT EC-1 . EGR Cooler Deleted . Edge Juice Platinum with Attitude . Blue Spring Upgrade . Sinister Diesel Coolant Filter. AFE Magnum FORCE PRO 5R Stage-2 CAI . Warn Premium Locking Hubs
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