P0628 FCA control

biggy238

biggy238

Active member
I'm starting this thread to keep the hardware issue out of the EFI thread.

P0628 Fuel Pump Control Circuit Low

I've ohmed from C1-6 to C1-19, with FCA connected. Wires have the minimum ohm load, 0.2. With the new FCA plugged in, that jumps to 3ohms, which is the resistance of the solenoid.

With an oscilloscope connected between the circuit and ground, I have between 6-7V constant. There is no pulse width taking place.

Paper clipping across the connector got me a P0251.

Pins on the ECM are ok. Sockets in the connector are seated.

I'm to the point that I think the ECM has a defect on the low side driver.

I'm also suspicious I have a problem on the MAP. It refuses to read ambient, and last time I looked, it was showing 5psi boost even aftert he sensor was re-scaled.

Anyone seen this before?
 
Both, running and not running.

Scope should be fast enough. I would have to look at the rate on it to be specific.

I didn't take a Pic of the computer screen

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fca0c19ea6f1cb6d2c12a14898bed506.jpg
 
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Not uncommon to see ECMs do a slow, random fail.
The 2nd gens and CM2100s are notorious for it.

The 849s are a better ecm, but age is the enemy on electronics.

Jus curious, but which RPS are you running?

Mark.
 
6.7L rail.
That was the basis for the other thread. I thought I had missed something in the file that was causing the ecm to be unhappy.

The truck will start and run at 26kpsi until I give it a significant throttle input. Then, the RP will drop to 11k and maintain that. It has a strong fuel knock in either case.



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Just throwing things out there, but aren't the pressure values different between a 6.7 and 5.9 RPS?

Mark.
 
Mark Nixon said:
Just throwing things out there, but aren't the pressure values different between a 6.7 and 5.9 RPS?

Mark.
Click to expand...
They are. I posted the other thread to make sure I was hitting all of the places in the software that need to change. I'm new to EFI, and the way that the PID works for the diag related to rail pressure.



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Well, unless I missed something, I'm sticking a fork in the ecm. The only check I hadn't done was put a headlamp in place of the fca to see if it would light. It will not.

C1-6 to FCA2 is 0.2ohm
C1-19 to FCA1 is 0.2ohm
FCA is 2.8ohm
C1-6 to C1-19 with FCA connected is 3.0ohm

Monitored voltage on C1-19 to FCA1 and had 7V constant with no pwm as seen with an oscilloscope and fluke.

Manual says disconnect the connector and install a lamp in place of the fca. I did that and have no light.

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I updated the file to use all of the fuel control PID's from an 08 engine.

It hit 28k cranking and immediately dropped back to 12Kpsi and idled there.

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Aaaaand. I transfered the rest of the data from the 08 fuel pressure file. I went out and flashed what I had done. Logged it, started the engine. 28kpsi.

Im done with this fora little while.

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ECM has a failed driver. Hung a test ecm, dialed right down to 7k and displays full mA output. Was at 14.7 constant before

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Mark Nixon said:
Like I have said, ECMs failing present some strange issues.

Glad you sorted it out. :cool:



Mark.
Click to expand...
They certainly do. This failure was more on the normal side for me, I just needed to be sure that I hadn't self-inflicted by using the 6.7 fuel system.

I had a cat ecm one time with an internal clock error. The engine would start and run on decreasing time intervals, the frequency of the ecm would change and everything would go nuts. Good times.

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