What Does U1798 Mean?
The module monitoring external door access (door ajar sensors, handle switches) is not acknowledging network messages. The system cannot confirm receipt of door status information.
Common Causes
35%
Failed door module or door ajar sensor module
30%
Damaged or broken wiring in door harness at hinge flex area
20%
Corroded or water-damaged door module or sensor connector
10%
Failed door ajar switch or latch assembly with integrated sensor
5%
Body control module or network communication fault
Diagnostic Steps
1
Step 1: Check power and ground circuits to door module and door ajar sensor
2
Step 2: Flex door wiring at hinge area while monitoring for intermittent loss of continuity or signal
3
Step 3: Remove door panel and inspect all connectors for corrosion, water damage, or terminal issues
4
Step 4: Use scan tool to monitor door ajar status in real-time while opening/closing door to verify sensor function
5
Step 5: Test SCP communication signals at door module to verify proper network operation
Estimated Repair Cost
$120 - $650
Parts + labor, varies by vehicle and location
The module monitoring external door access (door ajar sensors, handle switches) is not acknowledging network messages. The system cannot confirm receipt of door status information.
The most common cause of U1798 (SCP (J1850) Lack of Acknowledgment for External Access (Doors)) is: Failed door module or door ajar sensor module
Typical repair costs for U1798 range from $120 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
May prevent interior lights from activating or cause false door ajar warnings. Could mask actual open door conditions while driving, posing safety risk.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U1798 to identify the root cause.
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Quick Info
Category
Network
System
Door Monitoring / Entry System
Difficulty
Type
Manufacturer
Recommended Tools
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