knkreb
11-05-2006, 09:16 PM
Electronics issues
Since we are owners of the first ever designed “electronic” diesel, we have the privilege to become experts on these engines. Since dealership support has faded out, and finding someone with knowledge about these engines is getting harder and harder, we have a deal for you… this thread, free of charge.
The ECM (Engine Control Module) or PCM (Powertrain Control Module) is the computer. Both terms are used somewhat interchangeably, but the 6.5L Diesel version is officially factory-designated as the PCM. It is at the mercy of several different factors, one of which is electricity (in DC) provided to it, others being the inputs and outputs related to it.
There have been a few PCM failures along the way, but for the most part, they are very reliable. Once in a great while someone will post a failure, but it is not that common.
There are some things that you can do to help with electronic problems that creep up. Here’s a listing of things to point you in the right direction.
Battery cables and connections. – Diesels are very hard on the electrical system. This is due to the fact that it takes so much torque to actually start the engine and add in glow plugs too, it becomes a significant electrical draw. Weak and mis-matched batteries create poor voltage, poor charging, and low cranking speed. Cranking speed is critical to getting an engine to start in a diesel application. Minimum RPM is 100.
Battery cables may look okay on the outside, but below the insulation surface, acid may have wicked it’s way down the cable, creating a very poor conductor.
Poor grounding
Several ground points are critical to PCM operation. Firewall to passenger head is a critical one, as well as the ground near the alternator to the injection pump.
Connections in general – Poor connections may appear fine from the outside. However, removal, cleaning and retightening may show a great improvement on the quality of the connection.
A failed connector will cause the same symptoms as failure of the device it is connecting to or from.
Chafed wires – these are hard to find. With a maze of wiring in all different directions, to be able to pin point an exact point of chafing is difficult, at best. Although these don’t seem to get posted as often as other problems, they do occur from time to time.
Chafed\loose wiring can also give symptom of device failure
Connectors – sometimes simply removing and reconnecting connectors will end up cleaning the connection and improving it’s performance. These connectors can be either directly connected to the PCM or elsewhere in the wiring harness.
Again, connector failure symptoms can be mistaken for device failure
The computer will not spit out a code for a PMD failure usually. There are a great many diagnostics built into the computer, but that was not one of them. Read up on PMD’s in the FAQ listing, or follow the link here.
Optical sensor problems (High resolution timing codes etc) The optical sensor resides on the top of the injection pump. Some may have the optical sensor filter harness on their pump. If you are having any codes that are indicating optical sensor codes, high resolution timing, etc, etc. try removing this filter harness from the top of the pump and plug the electrical wiring harness directly into the pump, less the filter. This may or may not resolve the issue.
Sometimes fuel supply issues can cause what appears to be an electronic issue. Sometimes you’ll see things that indicate a failing injection pump (injection pump related codes) Before thinking the worst, insure that all systems are properly operating. Poor fuel supply can create what appear to be other problems. Work out the easy stuff first, then work your way up to the more expensive things as needed. No need in spending $1200 when you only have a $100 lift pump problem
There is a thread in the FAQ's that talks about how to understand PCM codes (http://dieselplace.com/forum/showthread.php?t=82807) Read up on it to understand what the computer sees and how it reacts. The code number is not the end all solution. It's just an indicator, not a diagnosis.
Since we are owners of the first ever designed “electronic” diesel, we have the privilege to become experts on these engines. Since dealership support has faded out, and finding someone with knowledge about these engines is getting harder and harder, we have a deal for you… this thread, free of charge.
The ECM (Engine Control Module) or PCM (Powertrain Control Module) is the computer. Both terms are used somewhat interchangeably, but the 6.5L Diesel version is officially factory-designated as the PCM. It is at the mercy of several different factors, one of which is electricity (in DC) provided to it, others being the inputs and outputs related to it.
There have been a few PCM failures along the way, but for the most part, they are very reliable. Once in a great while someone will post a failure, but it is not that common.
There are some things that you can do to help with electronic problems that creep up. Here’s a listing of things to point you in the right direction.
Battery cables and connections. – Diesels are very hard on the electrical system. This is due to the fact that it takes so much torque to actually start the engine and add in glow plugs too, it becomes a significant electrical draw. Weak and mis-matched batteries create poor voltage, poor charging, and low cranking speed. Cranking speed is critical to getting an engine to start in a diesel application. Minimum RPM is 100.
Battery cables may look okay on the outside, but below the insulation surface, acid may have wicked it’s way down the cable, creating a very poor conductor.
Poor grounding
Several ground points are critical to PCM operation. Firewall to passenger head is a critical one, as well as the ground near the alternator to the injection pump.
Connections in general – Poor connections may appear fine from the outside. However, removal, cleaning and retightening may show a great improvement on the quality of the connection.
A failed connector will cause the same symptoms as failure of the device it is connecting to or from.
Chafed wires – these are hard to find. With a maze of wiring in all different directions, to be able to pin point an exact point of chafing is difficult, at best. Although these don’t seem to get posted as often as other problems, they do occur from time to time.
Chafed\loose wiring can also give symptom of device failure
Connectors – sometimes simply removing and reconnecting connectors will end up cleaning the connection and improving it’s performance. These connectors can be either directly connected to the PCM or elsewhere in the wiring harness.
Again, connector failure symptoms can be mistaken for device failure
The computer will not spit out a code for a PMD failure usually. There are a great many diagnostics built into the computer, but that was not one of them. Read up on PMD’s in the FAQ listing, or follow the link here.
Optical sensor problems (High resolution timing codes etc) The optical sensor resides on the top of the injection pump. Some may have the optical sensor filter harness on their pump. If you are having any codes that are indicating optical sensor codes, high resolution timing, etc, etc. try removing this filter harness from the top of the pump and plug the electrical wiring harness directly into the pump, less the filter. This may or may not resolve the issue.
Sometimes fuel supply issues can cause what appears to be an electronic issue. Sometimes you’ll see things that indicate a failing injection pump (injection pump related codes) Before thinking the worst, insure that all systems are properly operating. Poor fuel supply can create what appear to be other problems. Work out the easy stuff first, then work your way up to the more expensive things as needed. No need in spending $1200 when you only have a $100 lift pump problem
There is a thread in the FAQ's that talks about how to understand PCM codes (http://dieselplace.com/forum/showthread.php?t=82807) Read up on it to understand what the computer sees and how it reacts. The code number is not the end all solution. It's just an indicator, not a diagnosis.