OBD-II Code U1216: Network Communication Failure

What Does U1216 Mean?

U1216 is a network communication code indicating a specific computer module is not talking to the rest of the vehicle. For Chrysler, Dodge, Jeep, and Ram vehicles, it means the Driver Assistance System Module (DASM) lost communication, disabling adaptive cruise control and automatic braking. For Nissan vehicles, it indicates a fault in the 4WD system's indicator light circuit.

Technical definition: The formal SAE/OBD-II definition for code U1216 is manufacturer-specific. Common definitions include: "Lost Communication With DASM (Driver Assistance System Module)" (Chrysler/Dodge/Jeep/Ram) and "Four Wheel Drive Low Range (4LO) Indicator Circuit" (Nissan).

Can I Drive With U1216?

⚠️Yes, But With Caution. You can drive, but limit trips to short, low-speed drives to a repair shop. U1216 disables critical safety features like Anti-lock Brakes (ABS) and Electronic Stability Control (ESC). In an emergency stop, your wheels will lock up, causing an uncontrollable skid. Continued driving does not cause direct component damage, but the collision risk is severe.

Common Causes

• Software Glitch / Outdated Module Firmware (Very Common) — Module software bugs cause communication dropouts. Ram 1500s have a massive recall (24V-653) specifically for an ABS software flaw that triggers U1216 and disables safety systems.
• Damaged or Corroded CAN Bus Wiring (Very Common) — CAN bus wires chafe, short, or corrode. Water intrusion from leaking windshields or clogged sunroof drains saturates harnesses, causing green copper corrosion that blocks network signals.
🎬 Watch: A master technician explains how to troubleshoot CAN bus faults.
• Low Voltage or Charging System Failure (Common) — Sensitive electronic modules require stable voltage above 12.4V. A dying battery or a failing alternator producing excessive AC ripple corrupts CAN bus data and drops modules offline.
• Faulty Control Module (e.g., DASM) (Common) — The module itself fails internally due to thermal stress or component degradation. Only suspect the module after verifying wiring, power, grounds, and network termination.
• Failed CAN Bus Terminating Resistor (Common) — The CAN bus requires two 120-ohm resistors at its physical ends to prevent signal echoes. If one fails, network resistance jumps to 120 ohms, causing total communication failure.
• Poor Ground Connection (Common) — Modules require a solid ground to function. A loose or rusty ground strap creates high resistance, causing intermittent communication errors.
• Connector Pin Fitment Issues (Less Common) — Female terminals inside a connector spread or loosen over time. This poor 'pin drag' creates an intermittent open circuit highly sensitive to road vibration.
• Blown Module Fuse (Less Common) — A blown power supply fuse instantly takes the module offline. This is usually a symptom of an underlying short circuit.

Symptoms

• Disabled Driver-Assist Features — Chrysler/Jeep displays show "ACC Unavailable Service Required 🎬 Watch: Diagnosing lost communication with modules on Chrysler and Jeep vehicles." or "AEB Unavailable". Adaptive cruise control and automatic emergency braking cease functioning.
• Multiple Dashboard Warning Lights — The Check Engine Light illuminates alongside ABS, traction control, and stability control warnings.
• 4WD System Warning Lights — On affected Nissan models, the 4WD warning light illuminates, preventing switching between 2WD and 4WD modes.
• Erratic Gauge Behavior — Instrument cluster gauges sweep randomly and dash lights flicker during widespread network crashes.
• Vehicle Stuck in Limp Mode — The ECU restricts engine power and locks the transmission into a single gear to prevent drivetrain damage.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this code.

Common Fixes & Costs

• Update Module Software (Recall/TSB) — Parts: $0, Labor: $0-$150, ~1.0 hr book time (Professional)
• Repair Damaged CAN Bus Wiring or Connectors — Parts: $10-$100, Labor: $250-$1200, ~3.0 hr book time (Professional)
• Replace the Driver Assistance System Module (DASM) — Parts: $500-$900, Labor: $250-$500, ~2.5 hr book time (Professional)
• Replace a Blown Fuse and Diagnose the Short — Parts: $1-$5, Labor: $125-$250, ~1.5 hr book time (DIY)

DIY vs Professional

• Update Module Software — Beginner:
• Repair Damaged CAN Bus Wiring — Beginner:
• Replace the DASM — Beginner:
• Replace a Blown Fuse — Beginner:

Used vs. New Parts: Buying Guide

When a used part is worth it: For safety-critical ADAS modules, favor new OEM parts. Used modules require expensive dealer programming and carry a high risk of internal failure.

Donor-vehicle mileage cap: roughly under 50000 miles for the part to have meaningful remaining life.

Donor quality checklist:

• Verify the donor vehicle's VIN to check its history for accidents or flood damage.
• Match the part number exactly. Superseded numbers may not always be backward compatible.
• Ask the seller if the part comes with any warranty (typically 30-90 days).

Decision logic:

• If The part is a safety-critical ADAS module like a DASM → Favor new OEM parts. The cost savings of a used part are erased by diagnostic and calibration issues.
• If The vehicle is over 10 years old and the budget is extremely tight → A used module is a viable risk, but factor in the potential cost of it failing to program.
• If You do not have access to a dealership or a qualified independent shop → Buy a new part. Many shops refuse to install customer-supplied used electronics.

Warranty tradeoff: Used parts typically have a 30-90 day parts-only warranty. A new OEM part installed by a dealer usually carries a 1-2 year warranty on both the part and the labor.

Worst-case if a used part fails: $500-$1000 if a used module fails to program, requiring repeat labor and the purchase of a new module anyway.

What Happens If You Wait — Timeline

1. Immediate: Critical safety systems (ABS, ESC) disable, drastically increasing the risk of an uncontrollable skid. (MPG impact: 0%% · Added cost: $0 (Safety risk is the primary cost))
2. 0-3 months: Unstable voltage from a failing alternator damages other sensitive electronic modules. (MPG impact: 0-5%% · Added cost: $200-$800)
3. 3-6 months: Unaddressed water leaks cause widespread harness corrosion, affecting multiple circuits. (MPG impact: 0%% · Added cost: $800-$1500)
4. 6+ months: Catastrophic harness failure requires complete dash removal and replacement. (MPG impact: N/A% · Added cost: $2000-$5000+)

Cost of Not Fixing It

• Immediate: Critical safety systems (ABS, ESC) disable, drastically increasing the risk of an uncontrollable skid. (Added cost: N/A (Safety Risk))
• 0-3 months: Unstable voltage from a failing alternator damages other sensitive electronic modules. (Added cost: $200-$800)
• 3+ months: Unaddressed water leaks cause widespread harness corrosion, requiring complete dash removal. (Added cost: $2000-$5000+)

Diagnosis Steps

1. Check for Other Trouble Codes
   Scan all modules. A general network code like U0001 indicates a bus-wide fault, while U0121 points to a specific ABS communication failure.
   Tools: OBD-II Scanner (capable of reading all modules) (Beginner)
2. Inspect Battery and Fuses
   Verify battery voltage exceeds 12.4V. Locate the fuse for the non-communicating module (e.g., DASM) and check for a blown filament.
   Tools: Multimeter, Basic Hand Tools (Beginner)
3. Perform a Visual Inspection of Wiring
   Inspect the harness leading to the affected module. On Chrysler/Jeep vehicles, check wiring near the DASM behind the rearview mirror and inspect footwells for water intrusion.
   Tools: Flashlight, Inspection Mirror (Intermediate)
4. Test CAN Bus Network Resistance
   Disconnect the battery. Measure resistance between OBD-II Pin 6 (CAN High) and Pin 14 (CAN Low). A healthy network reads 60 ohms. 120 ohms indicates an open circuit; 0 ohms indicates a short.
   Tools: Multimeter (Intermediate)
5. Check for Power and Ground at the Module
   Unplug the suspect module. Use a multimeter to verify battery voltage on the power pins and ensure ground resistance is under 0.5 ohms to the negative battery terminal.
   Tools: Multimeter, Wiring Diagram (Advanced)
6. Check CAN Bus Voltages at the Module
   With the ignition on, measure DC voltage at the module connector. A healthy bus shows 2.6V-2.7V on CAN High and 2.3V-2.4V on CAN Low. Missing voltages confirm a wiring fault.
   Tools: Multimeter, Wiring Diagram (Advanced)
7. Isolate the Faulty Module
   If CAN resistance is incorrect, unplug modules one by one. When resistance returns to 60 ohms, the last unplugged module is internally shorted.
   Tools: Multimeter, Basic Hand Tools (Advanced)
8. Perform a 'Pin Drag' Test
   Test female terminals in the module connector for proper tension using a correctly sized male test pin. Terminals offering zero resistance must be replaced.
   Tools: Terminal Pin Test Kit (Advanced)
9. Check for AC Ripple Voltage
   With the engine running at 2000 RPM, measure AC Volts across the battery terminals. Readings above 0.5V indicate a failing alternator corrupting the network.
   Tools: Multimeter (Advanced)
10. Perform Oscilloscope Waveform Analysis
    Connect a two-channel scope to CAN High and Low. A healthy bus shows a clean, mirror-image square wave. This definitively identifies signal interference and shorts.
    Tools: Automotive Oscilloscope, Back-probe Pins (Professional)

When This Code Triggers (Freeze-Frame Conditions)

• Engine Coolant Temp: 180-200°F (82-93°C) (Sets when the vehicle is fully warmed up, often exposing thermal expansion faults in wiring or modules.)
• Vehicle Speed: 35-55 mph (56-88 km/h) (Logged during steady-state driving when the ECU expects continuous communication from active modules.)
• RPM: 1500-2500 (The fault is frequently logged during normal cruise or steady throttle application.)
• Control Module Voltage: 13.5-14.5V (Captures system voltage at the moment of failure; values below 12.4V point directly to a battery or alternator issue.)

Related Codes

• U0001 — High Speed CAN Communication Bus. Indicates a network-wide fault, not an isolated module issue.
• U0121 — Lost Communication With ABS. Often triggers alongside U1216 due to shared network architecture or software bugs (e.g., Ram recall).
• C0089 — Adaptive Cruise Control Cancel Switch. Appears when ACC fails due to lost DASM communication.
• U0403 — Invalid Data Received From Transfer Case Control Module. Appears on 4WD vehicles during network-wide communication drops.

Climate & Environmental Factors

• High Humidity / Rain: Moisture seeps into compromised wire insulation or connectors, causing shorts and high resistance that block CAN bus signals.
• Road Salt (Winter Climates): Corrosive salt brine accelerates the degradation of wiring, connectors, and ground points, leading to rapid communication failures.
• Extreme Heat: High temperatures expand electrical components, exposing micro-fractures in solder joints within control modules and causing intermittent faults.
• Extreme Cold: Freezing temperatures make wiring insulation brittle and prone to cracking, while also disrupting the timing oscillators inside control modules.

How to Talk to a Mechanic About This Code

Say this: "I'm scheduling a diagnostic for a U1216 network code. Please authorize one hour to test CAN bus resistance, module power, and grounds before recommending any part replacements."

This signals to the shop that you understand this is a complex electrical issue, not a simple part swap. It directs them to perform a logical diagnostic process.

Avoid saying:

• 'My check engine light is on, can you fix it?' (Too vague, invites upselling)
• 'I think I need a new computer.' (Don't diagnose the car for them)
• 'Just do whatever it takes to fix it.' (Invites a blank check)

Questions to ask before authorizing the repair:

• What specific tests did you perform to isolate the failure?
• Did you verify power, ground, and network signals at the module's connector?
• Can you show me the damaged wiring or explain the test results that condemn the module?
• Does the quote include mandatory ADAS calibration?

Where to Take It: Dealer vs Independent vs Chain

• Dealer: Recommended, especially if ADAS calibration is needed. They have manufacturer-specific tools and information.
  Best for: Vehicles under warranty, Known recall-related issues (e.g., Ram 1500 software update), Complex ADAS calibration is required after the fix
  Downsides: Highest labor rates, May be less willing to perform intricate wiring repairs and favor module replacement (Typical cost: +50% vs. baseline)
• Independent Shop: Best fit, but ONLY if you find a shop that specializes in automotive electrical and CAN bus diagnostics.
  Best for: Out-of-warranty vehicles where cost is a major factor, Shops with a known reputation for excellent electrical diagnostics
  Downsides: Quality and expertise vary widely. Must be vetted carefully., May not have the expensive, specialized equipment for ADAS calibration. (Typical cost: +0% vs. baseline)
• Chain Shop: AVOID. This type of repair is far outside their business model and expertise.
  Best for: Simple, unrelated maintenance like oil changes or tires.
  Downsides: Technicians lack training and equipment for complex network tracing., High pressure to sell parts and services quickly. (Typical cost: -10% vs. baseline)

When to Walk Away From the Repair

If the estimated repair cost exceeds 40-50% of the car's Kelley Blue Book (KBB) private-party value, consider selling.

• Car worth $3500, fix is $2200: Walk away. The repair cost is over 60% of the vehicle's value. This is a classic 'mechanic special' to sell as-is.
• Car worth $18000, fix is $1500: Fix it. The repair cost is less than 10% of the vehicle's value and restores critical safety features.
• Car worth $8000, fix is $3500: Borderline. At 44% of the car's value, this is a tough call. Get a second opinion and evaluate the car's overall condition before proceeding.

What Scan Tool You Need for This Code

Minimum: A scanner that can perform a 'full system scan' or 'all module scan'. It must be able to read manufacturer-specific codes from the ABS, BCM, and other modules, not just generic engine codes.

A basic $20 code reader only communicates with the Engine Control Module (ECM) for emissions-related codes. It cannot see other modules like the DASM or ABS, making it completely blind to the source of a U1216 code.

Budget: BlueDriver Pro (~$99) — Performs full system scans to identify the non-communicating module.

Mid-range: Autel MK808 / Foxwell NT510 Elite (~$150-350) — Offers bidirectional controls to command components and verify wiring integrity.

Professional: Autel MK808BT / Launch X431 Series (~$450-1200) — Provides advanced diagnostics, special routines, and ADAS calibration initiation.

Rent vs buy: Auto parts store rental scanners are typically basic code readers and will NOT be sufficient for this code. If you are serious about diagnosing this yourself, you must buy a scanner with 'all system' capabilities.

How to Clear the Code After You Fix It

1. Reconnect the battery if it was disconnected for repairs.
2. Use an OBD-II scan tool to perform a 'Clear Codes' function on all modules.
3. Perform a complete drive cycle to allow the vehicle's readiness monitors to run their self-tests.

Drive cycle (~30 minutes): Cold start (sat 8+ hours). Idle 3 minutes. Drive 20 minutes mixed city/highway, including 5 minutes steady at 55 mph. Cool down completely.

Readiness monitors affected: Comprehensive Component Monitor, CAN Communication

Before emissions retest: drive at least 100 miles to fully set monitors.

Watch out for:

• Disconnecting the battery resets readiness monitors to 'Not Ready', causing an automatic emissions failure.
• The code returns immediately if the broken wire or loose pin isn't fixed.

Will This Fail Emissions / State Inspection?

Yes — this code typically fails an OBD-II emissions inspection.

• California: Illuminated Check Engine Light is an automatic failure. Readiness monitors must be set post-repair.
• New York: Illuminated Check Engine Light is an automatic failure. Readiness monitors must be set post-repair.
• Texas: Illuminated Check Engine Light is an automatic failure. Readiness monitors must be set post-repair.

Most Commonly Affected Vehicles

• Ram 1500 (2019-2024) — Highly prone to DASM communication failures. Recall 24V-653 fixes an ABS software bug that disables ESC and triggers U1216.
• Jeep Grand Cherokee (2021-2024) — Subject to multiple TSBs for communication codes and DASM calibration failures.
• Dodge Challenger (2016-2023) — U1216 specifically defines as 'Lost Communication with DASM', frequently caused by front-end wiring damage.
• Chrysler Pacifica (2017-2024) — Experiences U1216 with 'AEB/ACC Unavailable' messages, pointing directly to DASM or network wiring issues.
• Nissan Armada (2017-2024) — U1216 refers to a 'Four Wheel Drive Low Range (4LO) Indicator Circuit' fault within the Transfer Case Control Module.

Manufacturer-Specific Notes

• Chrysler/Dodge/Jeep/Ram: Windshield replacement requires DASM recalibration. Failure to calibrate triggers U1216.
• Ram: Recall 24V-653 fixes an ABS software bug causing U1216 in 2019-2024 Ram 1500s.
• Nissan: Low Intelligent Key fob battery keeps the BCM awake, draining the main battery and triggering communication codes.
• General (All): Thermal expansion causes intermittent failures. Solder joint micro-fractures fail when hot and work when cold.

Real Owner Stories

2021 Ram 1500 at 45K miles

Multiple dash lights (ABS, ESC, ACC) appeared at startup. Adaptive cruise and emergency braking were unavailable.

What they tried:

1. Owner checked battery and fuses, which were all good.
2. Took vehicle to the dealer.

Outcome: Dealer diagnosed the issue as FCA Recall 75B (NHTSA 24V-653). They performed a free software update on the ABS module, resolving all codes. Total cost was $0.

Lesson: For late-model Ram trucks, always check for recalls first. Symptoms perfectly mimic a hardware failure, but the fix is a free software flash.

2018 Chrysler Pacifica at 70K miles

Intermittent 'ACC/AEB Unavailable' message on hot days. Code U1216 was stored.

What they tried:

1. A general repair shop quoted $1,400 for DASM replacement and calibration.
2. Owner sought a second opinion at an electrical diagnostic shop.

Outcome: The second shop performed a wiggle test on the harness near the DASM and found a loose pin in the main connector. Repairing the pin tension cost $350. The DASM was perfectly fine.

Lesson: Never replace an expensive module without verifying its connections. Intermittent, heat-related issues almost always point to wiring.

2020 Jeep Grand Cherokee at 60K miles

U1216 appeared immediately after the windshield was replaced by a third-party glass company.

What they tried:

1. The glass company claimed they performed a calibration.
2. Owner took the vehicle to the Jeep dealership.

Outcome: The dealership found the DASM calibration had failed. They re-ran the ADAS calibration procedure for $450. The glass company's equipment was inadequate.

Lesson: After a windshield replacement, insist on a successful ADAS calibration report. If codes appear, you must visit a dealer or certified ADAS shop.

2019 Dodge Durango at 85K miles

Vehicle had damp passenger carpets. Weeks later, the dash lit up with multiple warnings and U1216.

What they tried:

1. DIY diagnosis found green corrosion inside a large wiring connector in the kick panel.

Outcome: A professional shop replaced several corroded wires and the connector. The source was a clogged sunroof drain. Wiring repair cost $800; fixing the drain cost $150.

Lesson: Address water leaks immediately. By the time electrical symptoms appear, expensive corrosion damage has already occurred.

How to Prevent This Code From Triggering

• Periodically clean sunroof and A-pillar drains (Once per year (spring/fall)) — Clogged drains cause water intrusion, which corrodes wiring harnesses and control modules in the kick panels.
• Apply dielectric grease to critical connectors (When performing other repairs in the area) — A thin layer of dielectric grease blocks moisture and oxygen, preventing pin corrosion that causes high resistance.
• Inspect and clean main battery and chassis ground points (Every 30,000 miles or during battery service) — A rusty ground connection creates unstable voltage for all modules. Removing corrosion prevents random communication codes.
• Avoid splicing aftermarket accessories into CAN bus wires (Always) — Improperly tapping into CAN bus wiring introduces electrical noise, corrupts data, and provides a path for water to enter the harness.
• Test battery health annually (Once per year (before winter)) — A weak battery providing unstable voltage is a primary cause of multiple communication codes.

Frequently Asked Questions

Can I fix a U1216 code myself?

Fixing U1216 is extremely difficult for a DIYer. Diagnosing network wiring requires specialized tools like an oscilloscope and advanced electrical knowledge. It is best left to a professional diagnostic technician.

What are common misdiagnosis mistakes with U1216?

The most common mistake is replacing an expensive control module without verifying its power, ground, and network connections. A broken wire or corroded ground is a much more frequent and cheaper cause than a failed module.

What is a CAN bus terminating resistor and why does it matter?

The CAN bus network requires a 120-ohm resistor at both physical ends to absorb signal energy and prevent data-corrupting electrical echoes. With two resistors in parallel, a healthy network measures exactly 60 ohms.

My scanner shows 120 ohms on the CAN bus. Is that good or bad?

Yes, a 120-ohm reading means one of the two terminating resistors is disconnected or failed. This guarantees severe communication problems and points directly to a broken wire or a faulty terminating module.

How much does it cost to diagnose a U1216 code?

Shops typically charge a diagnostic fee of $125 to $200 for the first hour. Complex network wiring issues often require 2 to 3 hours of tracing, pushing initial diagnostic costs to $300-$500.

My adaptive cruise control stopped working after I got a new windshield. Is this related?

The forward-facing camera (DASM) is mounted to the windshield and requires mandatory recalibration after replacement. If the glass installer skipped this step or the calibration failed, it triggers U1216 and disables the system.

Can aftermarket accessories like a remote starter or stereo cause a U1216 code?

Yes. Improperly splicing aftermarket accessories into the CAN bus introduces electrical noise and corrupts network data. It also creates entry points for water, leading to harness corrosion.

Key Takeaways

• Code U1216 indicates a network communication failure, most commonly pointing to a disconnected Driver Assistance System Module (DASM) in Chrysler, Dodge, and Jeep vehicles.
• Always check for manufacturer recalls first; Ram 1500s (2019-2024) have a free software update (Recall 24V-653) that permanently fixes this code.
• A healthy CAN bus measures exactly 60 ohms; a reading of 120 ohms guarantees a broken wire or missing terminating resistor.
• Never replace an $800 control module without first verifying it receives stable battery voltage (above 12.4V) and has a ground resistance under 0.5 ohms.