Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSDODGE AND RAM2005MAGNUM V6-2.7L VIN RREPAIR AND DIAGNOSISA L L DIAGNOSTIC TROUBLE CODES ( DTC )TESTING AND INSPECTIONU CODE CHARTSU0100BODY CONTROL SYSTEM
2005 Dodge and Ram Magnum V6-2.7L VIN R
Body Control System
2005 Dodge and Ram Magnum V6-2.7L VIN RSECTION Body Control System
U0100-LOST COMMUNICATION WITH ECM/PCM
WHEN MONITORED
- With the ignition on
- Battery voltage between 10 and 16 volts
- IOD fuse installed
- FCM is configured correctly
SET CONDITION
Bus messages not received from the ECM/PCM for approximately 500ms.
POSSIBLE CAUSES
- CAN B or CAN C BUS circuits open or shorted
- DTCs related to battery voltage, ignition, or VIN messages
- FCM not configured correctly
- ECM/PCM
- ECM/PCM power and ground
- Module that set this DTC
DIAGNOSTIC TEST
1. VERIFY DTC IS ACTIVE
NOTE: Ensure the IOD fuse is installed and battery voltage is between 10 and 16 volts before proceeding.
With the scan tool, read active DTCs.
Q: Is this DTC active?
YES: Go To 2
NO: Refer to the Stored Lost Communication test procedure. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
2. CHECK FOR ANY OF THE FOLLOWING ACTIVE DTCs
With the scan tool, read all active DTCs from all modules.
NOTE: Check for FCM configuration, CAN B or C hardware electrical, VIN Missing/Mismatch, battery or ignition related DTCs.
Q: Does the scan tool display any active DTCs to the conditions listed above?
YES: Diagnose and repair the DTC. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 3
3. VERIFY THAT THE ECM/PCM IS ACTIVE ON THE BUS
Turn the ignition on.
With the scan tool, select Network Diagnostics.
Verify that the ECM/PCM is active on the bus.
Q: Is the ECM/PCM active on the bus?
YES: Go To 4
NO: Refer to Manufacturer Code Charts / Communication. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
4. CHECK FOR ADDITIONAL COMMUNICATION RELATED DTCs
With the scan tool, select Network Diagnostics.
Q: Is there more than one module with active DTCs "Logged Against" the ECM/PCM?
YES: Replace/update the ECM/PCM. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Replace/update the module that set this DTC. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
U0100-Lost Communication With ECM/PCM:
WHEN MONITORED
- With the ignition on
- Battery voltage between 10 and 16 volts
- IOD fuse installed
- FCM is configured correctly
SET CONDITION
Bus messages not received from the ECM/PCM for approximately 500ms.
POSSIBLE CAUSES
- CAN B or CAN C BUS circuits open or shorted
- DTCs related to battery voltage, ignition, or VIN messages
- FCM not configured correctly
- ECM/PCM
- ECM/PCM power and ground
- Module that set this DTC
DIAGNOSTIC TEST
1. VERIFY DTC IS ACTIVE
NOTE: Ensure the IOD fuse is installed and battery voltage is between 10 and 16 volts before proceeding.
With the scan tool, read active DTCs.
Q: Is this DTC active?
YES: Go To 2
NO: Refer to the Stored Lost Communication test procedure. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
2. CHECK FOR ANY OF THE FOLLOWING ACTIVE DTCs
With the scan tool, read all active DTCs from all modules.
NOTE: Check for FCM configuration, CAN B or C hardware electrical, VIN Missing/Mismatch, battery or ignition related DTCs.
Q: Does the scan tool display any active DTCs to the conditions listed above?
YES: Diagnose and repair the DTC. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 3
3. VERIFY THAT THE ECM/PCM IS ACTIVE ON THE BUS
Turn the ignition on.
With the scan tool, select Network Diagnostics.
Verify that the ECM/PCM is active on the bus.
Q: Is the ECM/PCM active on the bus?
YES: Go To 4
NO: Refer to Manufacturer Code Charts / Communication. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
4. CHECK FOR ADDITIONAL COMMUNICATION RELATED DTCs
With the scan tool, select Network Diagnostics.
Q: Is there more than one module with active DTCs "Logged Against" the ECM/PCM?
YES: Replace/update the ECM/PCM. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Replace/update the module that set this DTC. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
RENDER: 1.0x
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.