First, the ICP is easy to get to (left head, at the front, by the Filter Housing) and easy to change. Look for evidence that engine oil is leaking through it by inspecting its electrical plug for oil. Also, you can simply unplug the ICP and the PCM will set a default value for the IPR to run with as a test too.
Next, the 1211 is ALL ABOUT the Hi-Pres oil system and can have several causes. Here's a good write-up;
P1211, P1212 Ford Powerstroke Diesel
Ford Diesels use oil pressure to drive the high pressure fuel injection system. The engine oil pump not only pumps oil to lubricate engine components, but also pumps oil into a reservoir to be used by the high pressure oil pump.
The high pressure oil pump pulls oil from the reservoir and raises the pressure to the point where it can pop open the injectors. The high pressure pump also increases the pressure of the diesel fuel so it can inject into the cylinders and vaporize quickly.
The oil pressure generated by the high pressure oil pump is regulated by an electric solenoid that is pulsed by the PCM. As this Injection Pressure Regulator (IPR) solenoid is powered and de-powered, a small shaft moves back and forth, allowing spurts of oil to flow into the high pressure oil lines The IPR can regulate pressures in excess of 3,000psi. The high pressure oil moves from the pump to the cylinder head through braided steel lines.
The PCM fires the diesel fuel injectors by energizing a solenoid coil in the injector. Unlike gas fuel injectors where the solenoid lifts a pintle off a seat to allow pressurized fuel to flow into the cylinder, the solenoid in Ford diesel fuel injectors allows high pressure oil to flow. Think of this like a doctor’s syringe. The pressurized oil pushes on the plunger of the syringe to “inject” the fuel through the injector and into the cylinder. Since the minimum psi required to open the injectors is 400psi, the PCM monitors the actual pressure of the oil going to the injector with an Injection Control Pressure (ICP) sensor. Using data from the ICP sensor, the PCM can adjust the pulse rate to the IPR.
Since the IPR operates off of a pulsed voltage, the amount of ON time versus OFF time is referred to as “duty cycle.” The high pressure pump can easily achieve pressures in excess of 3,000psi. But it’s up to the IPR to regulate the amount of pressure going to the injectors. The IPR can regulate a 3,000 psi reading with no more than a 12% duty cycle. Yet, the PCM is capable of providing up to a 60% duty cycle to the IPR. However, once it reaches 50%, the PCM sets a trouble code P1211 or P1212 for “ICP above/below normal.
If you receive this code, your first step is to check the oil level in the crankcase. Since the entire high pressure system depends on having enough oil in the reservoir, a drop in oil level of 3 or more quarts can bring the system to a quick stop. Unlike a gasoline engine where the oil pressure sending unit is located in the engine block in an oil gallery, the oil pressure sending unit on a Ford Diesel is located in the top of the high pressure oil reservoir. In other words, Ford wants to make sure the high pressure oil reservoir is getting good oil pressure. If the oil “idiot” light does not go out the high pressure oil reservoir isn’t getting enough pressure. The high pressure pump cannot produce high pressure if it’s not getting enough oil from the engine oil pump. If the oil level checks out and the oil pressure light goes out, move on to the rest of the checks.
The PCM monitors RPM during cranking. As soon as RPMs reach 150, the PCM activates the IPR to begin regulating oil pressure. At the same time, the PCM starts monitoring the ICP sensor to double check oil pressure buildup. As mentioned earlier, the PCM can command up to a 60% duty cycle for the IPR. But if the PCM is providing maximum duty cycle and the ICP reports either less than 400psi or 2,000-2,500psi, and the engine is not running, it concludes there is a problem (a reading of 2,000-2,500 is a programmed “default” reading the PCM provides on the scan tool when it believes there’s a fault in the ICP). If you see 2,000-2,500psi on the ICP scan tool readout AND the engine isn’t running, you should suspect a bad ICP sensor.
If the engine won’t start, you can conclude there’s a problem in the high pressure system. Either the high pressure pump isn’t working, IPR is faulty, or there’s a large leak somewhere in the system that’s preventing pressure buildup. To eliminate a cylinder head leak from the troubleshooting process, remove the high pressure line from the right side head and cap it with a plug that can hold 3,000psi. Then remove the high pressure line from the left side cylinder head and attach a high pressure (3,000psi or more) gauge to the line. Then crank the engine and watch the pressure gauge. If you get a low reading, the problem is either a faulty high pressure pump or a bad IPR. First you must replace the IPR. If the problem still exists, replace the high pressure pump.
A P1211 can be related to several things, not just a chip. Some examples are...
1. Weak HPOP (Extremely common in high-milers)
2. Clogged screen (Also pretty common in poorly maintained vehicles)
3. Leaking ICP sensor (Causes ICP to read lower than expected)
4. Weak IPR solenoid (Difficulty maintaining ICP)
5. Stuck IPR valve (Causes excessive ICP)
6. Excessive Pulsewidth in chip calibration (Very common with aggressive tuning)
7. Inadequate IPR control in chip calibration (Also very common in aggressive tuning)
P1316, P1282, P1211 on Ford Powerstroke Diesel
Owners report trouble codes P1316, P1282, P1211 on Ford Powerstroke Diesel along with skipping or misfire symptoms. Install a scan tool to read the “duty cycle” specs for the Injection Pressure Regulator (IPR) and the Injection Control Pressure (ICP) sensor. The high pressure oil pump is capable of putting out more than 3,000psi. But the IPR regulates the amount of pressure with a solenoid that is pulsed open and closed by the PCM. The PCM reads the oil pressure from the ICP and commands the IPR on and off. The IPR can regulate 3,000psi with only a 12% duty cycle. So you should check both the ICP and IPR readings on the scan tool. If the psi reading on the ICP goes up while the IPR duty cycle goes down (12% or lower), that indicates a faulty or sticking IPR. The reason is that the PCM can no longer shut down the duty cycle enough to properly regulate the oil pressure. The IPR has a reasonably high failure rate.