Vehicle: 2014 Chrysler Town & Country Limited 2.8L Diesel (RHD)
Concern: Repeated dead battery / overnight discharge
The Customer Complaint: “The Battery Keeps Going Flat”
The owner reported:
- Repeated flat battery
- Vehicle sometimes fine, sometimes dead in the morning
- Alarm horn disconnected due to random night-time activations
This is a classic phantom drain scenario, often misdiagnosed as:
- Faulty battery
- Alternator failure
- Random electrical glitch
However, proper diagnostics told a very different story.
Step 1: Charging System & Base Electrical Health Verified
Before chasing parasitic drain, the fundamentals were confirmed.
Charging System:
- Engine running voltage: 14.05 – 14.1V
- Alternator output stable
- No charging faults present
Static Parasitic Draw:
- Measured at 0.03A
- Within normal sleep-mode specification
This immediately ruled out:
- Alternator fault
- Excessive constant drain
- Immediate hard short
The system behaved correctly when asleep.
That was the key.
Step 2: System-Wide Low Voltage History Found
A full system scan revealed widespread stored low-voltage DTCs across multiple modules:
- P0562 – System Voltage Low (PCM & TCM)
- B210D – Battery Voltage Low
- B210A – System Voltage Low
- Additional voltage-related codes in ABS, AMP, door modules, TPMS
This confirmed repeated historical deep-discharge events.
Important distinction: These were stored faults, not active faults.
The vehicle had been suffering battery drain episodes, but not due to a constant static load.
Step 3: The Only Active Fault – U110D
After clearing codes and rechecking, only one critical fault remained active:
U110D – Lost Communication With Security Siren
Located in the Intrusion Transceiver Module (ITM)
This was the breakthrough.
Why U110D Matters More Than It Looks
The security siren on this model contains:
- Its own internal backup battery
- Internal electronics
- A communication link to the alarm module
When the siren’s internal battery fails (very common on this platform), it can:
- Leak internally
- Cause communication failure
- Trigger false alarm events
- Prevent the CAN network from entering deep sleep
The vehicle then experiences:
- Random network wake-ups
- Module activation spikes
- High current draw during alarm-trigger events
Since the horn was disconnected to stop night-time noise, the only visible symptom was: A dead battery the next morning.
Why Static Drain Testing Didn’t Show the Fault
Static parasitic draw was normal at 0.03A.
That’s because the drain was event-based, not constant.
When phantom alarm triggers occur:
- The CAN network wakes up
- Multiple modules activate
- Current draw spikes significantly
- Battery discharges rapidly
Once the system returns to sleep, readings appear normal again.
This is why intermittent alarm-related drains are often misdiagnosed.
Hood Switch & Sensor Inputs Verified
To rule out false triggers:
- Hood ajar switch tested correctly
- Voltage reading within specification
- No abnormal input signals detected
The siren communication fault remained the only active network issue.
Root Cause Identified
The diagnostic evidence confirms:
- Charging system operating correctly
- Static parasitic draw within limits
- Repeated historical deep discharge
- Active U110D communication failure
- Phantom alarm wake-up behaviour
The most probable root cause: Internal failure of the alarm siren unit.
On RHD 2014 Chrysler Town & Country models, the siren is typically located:
- Behind the left front wheel arch liner
- Between the inner arch and front bumper cavity
Access requires partial removal of the wheel arch liner.
Why Battery Replacement Alone Won’t Fix It
The vehicle battery has experienced repeated deep discharge events.
Even though charging is correct:
- Internal battery health is likely compromised
- Capacity may be reduced
- Reliability will suffer
Two actions are required:
- Replace or repair the security siren
- Replace the vehicle battery
Fixing one without the other risks recurrence.
Why This Case Study Matters
This job highlights several key points:
- Normal static parasitic draw does not rule out intermittent drain
- Alarm sirens with internal batteries commonly fail
- Phantom alarm wake-ups can drain a battery overnight
- U110D is not just a communication fault, it can cause network instability
- Deep sleep failures on CAN systems are often security-related
Without structured diagnostics, this would have resulted in:
- Multiple battery replacements
- Continued breakdowns
- Ongoing frustration
Instead, the root cause was isolated correctly.