Medium and Heavy Trucks
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Hi my name is***** will be glad to help. Tha fault is for ECM power or loss of communication from your ECM. What model chassis is this?
Hi, Thanks for the update. I understand. It is the same for me here actually. We can post back and forth as needed.
Start at the battery box and look for corrosion in the harness and connectors and for faulty inline fuses between the battery box and ECM. Check the battery to starter connections including all grounds.
Thanks for the update... check your relays too including the IDM relay.... they are known for problems and corrosion
ICP sensor ? Is that 254 fault still active? Check the IDM and IDM relay and harness for problems if so
Click here for the diagrams.
The IDM will be on the firewall engine drivers side. Click here and see PDF page 57 Id try bypassing or changing the IDM relay and confirm power to the IDM or you have a possibly faulty IDM or ECM if the harness and relays check ok and there is good power and ground. See if you can access a test IDM or ECM from a possible salvage yard etc....
There should be power to it with the IGN switch on. If not then go to the IDM relay and check it or try bypassing it
Possibly faulty IDM relay or harness problem
The relay should be on the firewall near the IDM. There should be two or 3 there.... The schematics will help identifying the correct one.
Pleasure to help
It will not read the module if there is no power and ground to the module and is not powered up. Verify your power and grounds first.... If ok and wont read or communicate, try a test module or have bench tested and reflashed to see if it will take a reflash or needs replacement.
Check the connections in the battery box. There should be some inline fuses coming off the POS cable for ECM power...... Test power to the engine ECM and verify ground and switched power. If ok and no communication, you have a bad ECM
go to pdf page 55
Ok Ignoring the wire numbers, lets try the PINS on the connector... See the schematic... Bat power leads to pin 25 switched power leads to pin 24........... 21, 22, and 41 are all on the power side of the circuit depending on the ECM relay position whether they are energized.
Grounds lead to 1,2,23, 42
Thanks for the update. that means the ECM had problems for sure from low voltage or other reasons but you have an intermittent power issue or grounds to the ECM still.... Possible short, corroded harness/poor connections or ignition power/ charging system issues.
Test all your batteries with a digital tester for dead cells etc, clean/inspect/tighten all cable connections and grounds from batteries to starter and chassis grounds. Test the charging system for any problems and for shorts or draws. If ok inspect the engine and ECM harness thoroughly and the connector pins in the harness and through the firewall for corrosion, etc.
sounds like you are gaining and it is likely the voltage issue caused the first ECM to fail over time.
Investigate further into that problem and circuit.
No gauge response at all? No power to the gauges or the gauges cycle with key on but do not work? Which ECM is hooked up? If the test one, Try having it programmed for your truck VIN and see if everything works.
But likely worked with the other ECM..... Have the ECM reflashed and tested by the dealer. Sounds like an ECM problem, harness/datalink or ESC cab controller problem. If they work with the other ECM it would have to be a problem with the ECM.
Thanks for the update. Let me know.