U015A – Lost Communication With Collision Avoidance Module

System: Network | Standard: ISO/SAE Controlled | Fault type: General

Definition source: SAE J2012/J2012DA (industry standard)

DTC U015A indicates a network communication problem involving the collision avoidance module. In plain terms, one or more other modules on the vehicle network have stopped receiving expected messages from that module, or they cannot exchange data with it reliably. Because vehicles differ in network layouts, module naming, and the exact conditions that set communication faults, the way U015A is detected (and what other codes appear with it) can vary by vehicle. Always confirm the affected module, network path, and diagnostic flow in the appropriate service information before replacing any parts. Treat U015A as an electrical/network-level fault until testing proves a specific hardware or software cause.

What Does U015A Mean?

U015A means Lost Communication With Collision Avoidance Module. Under the SAE J2012 DTC framework, a “U” code is a network-related diagnostic trouble code. For U015A, the reporting module has determined that communication with the collision avoidance module is not occurring as required—typically because the expected network messages are missing, invalid, or not acknowledged within the monitor’s criteria. This code does not, by itself, prove the collision avoidance module has failed; it only confirms a communication loss condition that must be isolated to the network, power/ground supply, connectors, or the module itself using test-driven checks.

Quick Reference

• Subsystem: Vehicle network communications path to/from the collision avoidance module (data bus and related power/ground support).
• Common triggers: Module stops transmitting, network bus disruption, module reset due to power/ground interruption, or connector/wiring faults causing message loss.
• Likely root-cause buckets: Harness/connector issues; network bus faults; power/ground supply problems; module internal fault; configuration/software issues (varies by vehicle).
• Severity: Potential safety-system impact; collision avoidance features may be limited or disabled, and warnings may be present.
• First checks: Scan for related U-codes, verify module presence on the scan tool, check battery health and fuses, inspect network connectors and grounds, and look for recent electrical work.
• Common mistakes: Replacing the collision avoidance module without verifying network integrity, ignoring power/ground to the module, or overlooking a shared splice/connector affecting multiple modules.

Theory of Operation

The collision avoidance module typically communicates with other modules over the vehicle data bus, sharing status, sensor interpretations, and coordination messages used for driver alerts and assistance functions. Other controllers rely on these periodic messages to confirm the module is online and operating, and they may also request information or send commands depending on vehicle design.

U015A sets when the monitoring module detects that expected communication with the collision avoidance module is missing or consistently invalid. Common pathways include an interruption of power or ground to the collision avoidance module (so it stops talking), a bus wiring fault (so messages cannot travel), or a connector issue creating intermittent network contact. Some vehicles may also set the code after a module reset event, low system voltage, or network congestion, so confirmation with testing and service information is essential.

Symptoms

• Warning message: Driver information display may show a collision avoidance/assist system warning or “system unavailable” notice.
• Indicator light: One or more assistance/safety indicators may illuminate depending on how features are grouped.
• Feature disabled: Collision avoidance-related functions may be reduced, limited, or switched off as a failsafe.
• Multiple U-codes: Additional network communication DTCs may appear in other modules, especially those sharing the same bus segment.
• Intermittent behavior: Alerts may come and go, often correlating with vibration, harness movement, or electrical load changes.
• No symptoms: The code may store as history if communication was briefly lost during low voltage, a reset, or a transient network disturbance.

Common Causes

• Open, high-resistance, or intermittent connection on the network wiring between the Collision Avoidance Module and the rest of the network (varies by vehicle)
• Connector issues at the Collision Avoidance Module: loose seating, poor terminal tension, corrosion, bent pins, or backed-out terminals
• Power feed fault to the Collision Avoidance Module (blown fuse, faulty relay, open in the supply circuit, or excessive voltage drop under load)
• Ground circuit fault for the Collision Avoidance Module (open ground, loose fastener, corrosion at ground point, or excessive voltage drop)
• Network circuit short to ground, short to power, or short between network lines that disrupts message traffic
• Aftermarket wiring changes or improper repairs that disturb network integrity or module power/ground
• Collision Avoidance Module internal fault or software issue (consider only after verifying network, power, and ground)
• Another module on the same network segment failing and preventing normal communication (bus-off condition or network-wide disruption)

Diagnosis Steps

Tools typically needed include a scan tool capable of full-module network scanning and reading communication status, a digital multimeter for voltage-drop and continuity checks, and vehicle-specific service information for connector pinouts and network topology. A breakout lead kit or back-probing pins can help with non-intrusive testing. If available, a data logger function in the scan tool is useful for capturing intermittent dropouts.

1. Verify the complaint and record data. Confirm U015A is present. Save freeze-frame/event data and note whether the code is current or stored. Document all other DTCs, especially network-related codes, low-voltage codes, and any codes indicating module resets.
2. Run a full network scan. Attempt to communicate directly with the Collision Avoidance Module using the scan tool. Note whether it is “no response/offline” or communicates intermittently. Identify if multiple modules are offline, which may indicate a network segment issue rather than a single module fault.
3. Check battery/charging status indicators. Without quoting specifications, verify system voltage is stable and the vehicle does not show signs of low-voltage events (recent battery disconnect, weak battery, charging system warnings). Network communication is sensitive to supply instability; correct power issues before deeper network diagnostics.
4. Perform a visual inspection of the module and harness. Locate the Collision Avoidance Module (location varies by vehicle). Inspect for harness strain, chafing, crushed wiring, signs of previous repairs, and connectors that are not fully seated. Pay close attention to areas near brackets, sharp edges, and moving components.
5. Inspect connectors and terminals carefully. Key off and follow service information for safe connector handling. Disconnect the module connector(s) and check for corrosion, moisture intrusion, bent pins, pushed-out terminals, and poor pin fit. Repair terminal issues as needed, then reconnect and ensure positive locking.
6. Verify module power feeds under load. With the module connected when possible (back-probing per service info), check that the module’s B+ and ignition/enable feeds are present. Perform voltage-drop testing across the feed path (from source to module pin) while the circuit is loaded; excessive drop indicates resistance in fuses, relays, splices, or wiring.
7. Verify module grounds with voltage-drop testing. Check ground integrity by measuring voltage drop from the module ground pin to the battery negative while the module is powered. If excessive, inspect and service the ground point (clean/tighten), then re-test. Grounds that look intact can still have high resistance.
8. Evaluate the network circuit integrity at the module. Using service information for the correct network type and pins (varies by vehicle), inspect for opens and shorts. With key off where required, perform continuity checks between the module connector and the next accessible network point; check for short-to-ground and short-to-power conditions on the network circuits.
9. Check for network disruption from other components. If multiple communication codes exist, isolate by disconnecting suspected modules on the affected network segment one at a time (following service info procedures) to see if communication returns. This can help identify a module or branch circuit pulling the network down.
10. Wiggle test for intermittent faults. With the scan tool observing module online/offline status or U015A status, gently wiggle the harness, connector, and nearby splices while monitoring for dropouts. If the fault toggles, focus on the area that induces the change and repair the wiring/terminal issue.
11. Clear codes and validate with a road test and logging. After repairs, clear DTCs and run a drive cycle appropriate to the vehicle while logging network/module status. Confirm the Collision Avoidance Module remains reachable and U015A does not return. If U015A returns and power/ground/network circuits test good, consider module software updates or module replacement per service procedures.

Professional tip: Treat U015A as a communication symptom first, not a confirmation of a failed module. Prove power, ground, and network integrity with voltage-drop testing and repeatable isolation steps before condemning the Collision Avoidance Module, and always re-check for additional network DTCs that can point to a shared splice, ground point, or a different module pulling the network down.

Possible Fixes & Repair Costs

Repair costs for U015A can vary widely because the fix depends on whether the collision avoidance module is actually offline, the network has a wiring/connector issue, or the problem is power/ground related. Labor and parts needs also vary by vehicle and access.

• Restore power and ground to the collision avoidance module: Verify and repair the module’s battery feed, ignition feed (if used), grounds, and related fuses/relays only after testing confirms a supply issue.
• Repair the network circuit fault: Fix opens, shorts, high resistance, or poor pin fit in the communication lines between the module and the rest of the network (exact circuits vary by vehicle).
• Service connectors: Clean, dry, and secure connectors; correct terminal tension/pin fit issues; repair damaged seals; and ensure proper connector locking where testing indicates intermittent contact.
• Correct harness routing damage: Repair chafing, crushed sections, or tension points that cause intermittent communication loss during vibration or steering/suspension movement.
• Module reset and configuration verification: After restoring stable power/network integrity, clear codes and perform any required network re-learn/setup procedures per service information (varies by vehicle).
• Replace the collision avoidance module only after confirmation: Consider replacement only if power/ground and network wiring are verified good and the module still fails to communicate during directed testing.

Can I Still Drive With U015A?

You may be able to drive with U015A, but treat it as a safety-related warning because collision avoidance features can be limited or disabled when the module is not communicating. If you also have brake/steering warnings, multiple network codes, a no-start, stalling, or reduced-power behavior, avoid driving and have the vehicle inspected promptly. Even when the vehicle seems to drive normally, increased following distance and cautious driving are recommended until the communication fault is repaired and verified.

What Happens If You Ignore U015A?

Ignoring U015A can leave collision avoidance functions unavailable or inconsistent, which may increase risk in situations where driver-assistance features would normally intervene or warn. The fault may also spread into additional network-related DTCs as other modules time out waiting for messages, complicating diagnosis later. Intermittent communication issues often worsen over time if caused by harness damage, poor terminal contact, or marginal power/ground integrity, potentially leading to repeated warnings and reduced system functionality.

Last updated: March 15, 2026

Vehicles Commonly Affected by U015A

• Vehicles equipped with forward-looking driver-assistance that includes collision avoidance functions.
• Platforms using a shared vehicle network where multiple modules exchange safety-related messages.
• Vehicles with front-end repairs or impacts that may disturb harness routing, connectors, or module mounting.
• Vehicles with recent battery service or low-voltage events where module power supply stability may be marginal.
• Vehicles operated in harsh environments that can accelerate connector corrosion or water intrusion (design and exposure vary by vehicle).
• Vehicles with aftermarket electrical additions that may affect power distribution, grounding, or network wiring if improperly installed.
• High-mileage vehicles where vibration and heat cycling can contribute to terminal fretting and intermittent contact.
• Vehicles with prior wiring repairs where splices or routing may create resistance, intermittents, or chafing points.

Always verify the final repair by confirming stable module communication across multiple key cycles and a road test, then re-scan the vehicle to ensure U015A and related network codes do not return.