U0284

Code

Generic U — Network/User

Lost Communication With Active Grille Air Shutter Module A

Brand: Generic

Type: U — Network/User

Views: UK: 61 EN: 436 RU: 142

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Page language: EN

Open or shorted CAN/LIN wiring to the Active Grille Air Shutter Module A
Poor or missing module power or ground (fuse, relay, connector issue)
Corroded, loose or damaged connectors at the module or harness
Failed Active Grille Air Shutter Module A (internal fault)
Faulty or missing CAN bus termination(s) or short between CAN high/low and power/ground
Software/configuration mismatch or module programming error

Related diagnostic trouble code stored (U0284) and possibly MIL or network message
Active grille shutters inoperative, stuck open or closed
Reduced fuel economy or engine cooling anomalies if shutters remain closed or open
On-screen message or system warning about grille shutter or network communication
Other modules on the same bus reporting communication errors or multiple U-codes

Read and record freeze frame and all stored U-codes and pending codes with a capable scan tool
Perform a visual inspection of the grille shutter module, connectors and nearby wiring for corrosion, damage or moisture
Check fuses and relays related to the grille shutter module power feed
Verify module power and ground with a DVOM at the module connector
Check for continuity and shorts between CAN High/Low and battery/ground for the harness to the module
Scan the CAN network to see if other modules respond and check for bus-off conditions or excessive errors

Typical CAN idle voltages: CAN High ≈ 2.5 V, CAN Low ≈ 2.5 V (recessive). Dominant state: CAN H ≈ 3.5–4.5 V, CAN L ≈ 0.5–1.5 V (vehicle dependent)
Typical CAN bus termination: ~60 ohms measured between CAN High and CAN Low (two 120Ω resistors in parallel)
Common CAN baud rates: 250 kb/s or 500 kb/s (verify vehicle-specific rate with scan tool)
Module supply voltage: vehicle battery voltage at module power pin (approx 12 V with key on)

Verify the code and gather context: record freeze frame, number of occurrences and whether code is current or historical
Perform a visual inspection of the module, harness and connector for damage, corrosion, water entry or pin damage
Check fuses and relays for the grille shutter module circuit; restore any blown fuses and retest communication
With the ignition on (or as specified), verify module power and ground at the module connector using a DVOM
Using a scan tool, attempt to communicate with the module. If the tool cannot connect, note any other network modules that are non-responsive
Measure CAN bus voltages at the module connector: verify idle voltages and then wiggle harness to reproduce the fault; if abnormal, isolate wiring and repair
Check termination resistance across CAN High and CAN Low with the key off; expected about 60 ohms. If not present, trace to missing/failed termination resistor or connector
If wiring and power/ground are good but the module is non-responsive, disconnect the module and measure for shorts to battery or ground on CAN lines; repair wiring as needed
If wiring and network are verified good and the module still does not respond, attempt module software update/reprogramming if available; if no change, replace the module
After any repair, clear codes and perform a road test or operation cycle to confirm the grille shutter functions and the U0284 code does not return