Troubleshooting this diesel "no-start" can be done from the front seat.electrical systems repair shop training technician training A/C training automotive aftermarket diesel FICM
This fine piece of Detroit engineering arrived at the shop on a tow strap, dead in the water. The battery voltage is very low, due to the owner cranking the engine trying to get it started. At this point, what would you do? Close your toolbox, lock it or jump up and down with joy with the anticipation of another challenge in your bay and money in your wallet?
When one of these money pits land in your bay, consider it a blessing. These vehicles are money; the real secret is being able to communicate with this machine and get it to give up its deep-down secrets.
The complaint on this truck is a cranks/no-start condition. Interviewing the vehicle owner did not get much information, other than he had parked the truck the night before and the next morning it would not start. The engine has been cranked and the battery voltage is so low the starter will only turn the engine very slowly. The batteries were charged and tested; the engine will crank, try to start, but will not complete the task. Hooking up a scan tool found several Diagnostic Trouble Codes (DTCs) stored in memory.
- P0335 = CKP circuit A fault
- P0340 = CMP circuit A fault
- P1378 = FICM voltage low
- P1379 = System voltage out of range
- U0105= Lost comm. with FICM
- P0611 = FICM performance fault
One objective in any diagnostic process is to get to the finish line in a quick and efficient manner. On the surface, this looks like a very complex problem. When I see several codes stored like this, I try to simplify the problem. I like to put the codes into a few different categories. Many times, this turns one large job into two or three small jobs, which can make the big job lighter and more fun.
Another thing I suggest is to make every diagnostic problem into a game like a murder mystery. As you are working your way through the problem or problems, you are picking up clues. You put your clues into files, and when you have enough evidence, you put the pieces of the puzzle together to prosecute the case. In this case, the P0335 and the P0340 codes can be set by extended cranking, so I will not pursue them at this time. These codes go into the "not needed at this time" file. The P1378 and the P1379 can be set by the low battery voltage; these codes go to the "not needed at this time file."
This only leaves two codes to start the diagnostic process with, the U0105 and the P0611. Both of these codes are FICM-related, and I feel these are the place to start our quest for information.
Before we get too far along with the diagnostic process, I think it would be good to discuss the theory of operation of this system, and find out what it takes to make one of these engines run. Knowing this will aid in making the diagnostic process quicker and more accurate.
The engine uses a Hydraulic Electronic Unit Injector (HEUI) fuel injection system. The system is built around the High Pressure Oil Pump (HPOP) that sits in the engine valley right under the turbocharger, which is located at the rear of the engine. High-pressure oil piping consisting of a Y pipe, branch tubes, stand pipes and injector rails carries the high-pressure oil between the HPOP and the fuel injectors. The high oil pressure that operates the fuel injectors is controlled with the Injector Pressure Regulator (IPR). It's mounted in the HPOP, and is a pulse width controlled valve controlled by the PCM.
The high-pressure oil is monitored by the Injector Control Pressure sensor (ICP), which gives the high-pressure rail feedback to the PCM. This can be considered a closed loop system. The engine is managed with a Powertrain Control Module (PCM) and the Fuel Injection Control Module (FICM). These two modules communicate with each other on a high-speed Controller Area Network (CAN) line. This engine uses a CKP and a CMP to report crankshaft position and camshaft position to the PCM. The engine will not start if these two signals are not in proper synchronization.
The FICM and the PCM communicate together to operate the injectors. These injectors are operated from a 48-volt power source that the FICM generates. The nice part about this system is that all of the needed information for engine operation is available on the scan tool, and can be seen in the PCM datastream.
For some of us guys and gals who love using a lab scope to figure out problems like this, we will be going through withdrawal symptoms, since the lab scope is not needed for this operation.
Standing at the front of the vehicle with the hood open, you might scratch your head wondering where things like the PCM and the FICM are. The FICM sits down under the engine cowl, behind the air filter and under the coolant degas bottle. The FICM is bolted to the top rear of the left valve cover using rubber grommets to isolate the module from engine vibration. With the degas bottle removed, you can see the FICM. The air filter is also easy to remove, and will make access to the FICM a lot easier.
With this information, there are two ways to go. You can pull up data on your scan tool, and give the engine a crank, or you can go to the DTCs that are saved to get a direction. I prefer looking at some of the DTCs and try to eliminate as many things as I can before I start cranking on the engine. I would suggest starting with the communication code U0105 and the P0611. The code description for the U0105 code is "lost communication with the FICM," and the P0611 code is "FICM performance." I have put these two codes together because both codes are for module performance and module communication, and both codes deal with the FICM module.
There are two basic things that all modules need to work properly: the proper power and the proper ground. Missing either one will cause a communication code in almost any module on a vehicle. Because I like to do the simple things first, I want to test the power and ground to the FICM. Looking at the engine compartment makes this job appear a little intimidating. The FICM is covered up with the degas bottle and the air filter. Even if these two parts were removed, it is very hard to gain access to the three plugs on the FICM to back pin the powers and grounds.
Earlier, I was talking about scanner PIDS. There are several voltage PIDS that will display on the scan tool. To make this job easier, we can use the scan tool from the front seat of the vehicle to do our initial module analysis. If the proper voltages are displayed on the scan tool, I can see no need to start digging around in that black dirty hole trying to back pin a connector that you can't even see. There is also another way to verify proper module operation, a bidirectional test of the module. The flowchart for troubleshooting the U0105 DTC directs the tech to clear the codes and run the KOEO (key off-engine off) injector buzz test. If this test passes, there is a pretty good chance that the FICM has the power and ground that it needs for proper operation.
The codes were cleared from the PCM memory and the KOEO injector buzz test was performed.
Codes set with the Injector Buzz Test were:
- P0261 = Injector No. 1 circuit low
- P0264 = Injector No. 2 circuit low
- P0267 = Injector No. 3 circuit low
- P0270 = Injector No. 4 circuit low
- P0273 = Injector No. 5 circuit low
- P0276 = Injector No. 6 circuit low
- P0279 = Injector No. 7 circuit low
- P0282 = Injector No. 8 circuit low
Harness problems are quite common on this engine, but I really doubt that there is a harness problem to all of the injectors. As we move through the diagnostic process, my mind keeps turning to a FICM with a problem.
When doing a cranks/no start diagnosis on this engine, you will need to be watching these data PIDs: FICM SYNC and SYNC. These PIDS tell you that the PCM and FICM are in proper synchronization, and that the CKP and CMP are properly synchronized. Both of these should display a YES while cranking. There are three FICM voltage PIDs that you should also monitor. They are FICM LPWR, FICM MPWR and FICM VWPR. The data displayed on the first two PIDs should be more than 10.5 volts, while the FICM MPWR should display very close to 48 volts during cranking. RPM should display around 150, ICP volts a minimum of 0.8 volts and IPR more than 30 percent.
The next test I like to run is to graph some engine data and crank the engine to see exactly what is going on with the hydraulic injection system, the CMP and CPM and the FICM. I selected FICM SYNC, SYNC, FICM VPWR, FICM MWPR, FICM LWPR, RPM, ICP volts, and IPR percentage on the scan tool screen, then the engine was cranked for a few seconds.
A note of caution when using PIDs "ICP desired pressure" and "ICP pressure": Both are calculated PIDs, and the pressure information can be wrong, especially on an extended cranks/no-start, so please keep this in mind. Concentrate on the ICP voltage PID. This voltage PID is always the data that the PCM is getting. There is nothing more frustrating than watching bad data, such as seeing 2500 psi of ICP and the engine not starting — all the while the ICP voltage is only reading 0.5 or 0.6 volts. The PCM will not pulse the fuel injectors until 0.8 volts of ICP are reached.
While cranking, all the data looked good except the FICM MPWR. The voltage starts off at 48 volts, but starts declining as the engine is cranked over. This dropping voltage proves that the FICM module is defective because it is the source of the voltage. By watching the other data that is displayed, I can tell that the high-pressure side of the injection system is working properly and the FICM has the proper power supply. At this point, a new FICM was ordered and the vehicle owner called to inform him of the needed repairs.
The degas bottle and the air filter were removed to gain access to the FICM, and a new module was installed. The IDS scan tool was used to program the new FICM, the PCM and the TCM. Now the engine starts and runs smoothly. The "after the repair" data proves out the new FICM has fixed the problem.
Albin Moore spent the first 21 years of his working life in the logging industry. In 1992, he made the transition to shop ownership and opened Big Wrench Repair in Dryden, Wash. Since opening the shop, he has moved the business to specialize in drivability problem analysis, both with gasoline and diesel vehicles. Albin is an ASE CMAT L1 technician, and brings with him 40 years of analyzing and fixing mechanical and electrical problems.