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24. Most FICMs fail with cold start issues, but my 6.0 has warm start issues. FICM cause this?


There could be a logic board issue with the FICM, but more common with warm start trouble is an issue with the high pressure oil pump or the plumbing that connects to it. The pumps typically fail around 140,000 to 180,000 miles in the 03's and early 04's and sadly are a bear to replace. What happens in these earlier models is that a leak occurs in the system (from a popped out check ball or other failure) and then the pump loses the volume in the system necessary to fire the injectors. New versions of these oil pumps substitute a plug in lieu of a check ball.

The other pieces and parts that fail are the snap to connect (STC) fitting from the pump to the plumbing, the standpipes (accessible under the valve covers), or the dummy plugs on the oil rail (also under the valve covers). If you have a late 2004 or newer truck, this is nearly certainly where you'll want to check.

Most with high pressure oil system issues have symptoms including rough idle, hard to start warm (10-12 seconds is common), lack of typical acceleration, bucking and jerking at lower RPMs when driving down the road (when the pump is spinning more slowly), and a complete elimination of issues when the accelerator is pressed down enough to cause a downshift (since the oil pump now spins faster thus building up more oil volume). Also common with HPOP failures is for misfires to jump from one cylinder to the next.

Key to the diagnosis is also that HPOP issues have a tendency to come and go with changes in engine RPM, versus FICM issues which are consistent at given operating temperatures. A collection of videos on the diagnosis using an air test can be found on YouTube. Part 2 is here with the wrapup here. An air test showing the leak at the fitting is here.

Of course, if you have a way to measure your IPR duty cycles and see 85% oo during cranking, this is a sure fire way to know that you've got a leak. If you don't see 500psi or more build-up of Injection Control Pressure (ICP) during cranking, then the ECM won't give the green light to allow a start either. The IPR should be close to 24 at hot idle and and 27 or so at cold idle.

If you don't have guages to measure ICP, you can use a digital volt meter to convert the voltage to PSI, as follows:

Press Sensor 
(PSI) (MPA) Voltage 
0 0 .02v 
200 1.5 .4v 
400 3 0.73v 
600 4 .96v 
800 5.5 1.2v 
1000 7 1.4v 
1200 8 1.6v 
1400 9.7 1.9v 
1600 11 2.1v 
1800 12.4 2.3v 
2000 13.8 2.6v 
2200 15.2 2.8v 
2400 16.5 3v 
2600 18 3.3v 
2800 19.3 3.5v 
3000 20.6 3.8v

Most see 1.3V-1.5V during cranking (900-1100psi).

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