U1198: Lost Communication with Door Module
The U1198 code indicates that the Body Control Module (BCM/GEM) has detected a loss of communication or invalid data on the SCP (J1850 VPW) bus from the driver or passenger door module (DDM/PDM). This fault prevents the operation of external access systems such as power door locks, folding mirrors, entry lighting, and perimeter alarms associated with the doors.
1. Commonly Affected Makes
2. Most Common Causes
- Faulty or unpowered door control module (DDM/PDM)
- Open or short circuit in the SCP bus wires (orange/black or orange/white) leading to the door
- Damaged, corroded, or loose terminals in the door boot harness connector
- Low battery voltage or excessive voltage drop during engine start
- Internal communication failure in the BCM/GEM
3. Symptoms You Will Notice
- Power door locks inoperative
- Folding mirrors not working
- Entry lighting and perimeter alarm malfunction
4. Step-by-Step Diagnosis
Check battery voltage and charging system; ensure voltage is stable above 12.6V and no excessive drop during cranking.
Inspect the door boot harness and connector for corrosion, broken wires, or loose terminals; repair as needed.
Test the SCP bus wires (orange/black and orange/white) for continuity and shorts to ground or power.
Verify power and ground at the door module (DDM/PDM); if missing, trace the circuit.
If all wiring and power are good, suspect a faulty door module or BCM; perform a network test with a scan tool.
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, the vehicle is generally safe to drive, but you may lose power door lock and entry functions. Have it diagnosed soon to avoid battery drain or further issues.
How much does it cost to fix?▼
Depending on the cause, repair costs range from $100 for a wiring repair to $500 or more for a door module replacement.