Code
U2199
Generic
U — Network/User
Lost Communication With Unknown Control Module
Views:
UK: 0
EN: 1
RU: 0
AI status
Completed
Completed
100%
Causes
- Disconnected or corroded connector for the unknown module
- Power or ground circuit fault to the module
- Damaged wiring harness or short on the vehicle communication bus (CAN/LIN)
- Missing or improperly configured module (aftermarket, removed, or not programmed)
- Faulty control module (internal failure)
- Bus wiring short to battery or ground or open circuit
Symptoms
- MIL or network-related warning lamps illuminated
- One or more vehicle systems inoperative or intermittent (depends on which module is missing)
- Other modules reporting multiple U-codes or network errors
- Inability of scan tool to identify a module or to communicate with all expected nodes
- Intermittent faults or faults present after recent wiring or module work
What to check
- Use a capable scan tool to read all stored U-codes and freeze frame data
- Perform a network node scan/discovery to list modules present on each bus
- Inspect connectors, pins and wiring for the suspected module/bus (corrosion, bent pins, disconnected plugs)
- Verify battery voltage and chassis/engine grounds at the module connector
- Measure CAN/LIN bus voltages with a multimeter or better with a lab scope
- Check termination resistor across CAN H and CAN L (~60 ohms total)
Signal parameters
- CAN bus idle voltages: CAN High ≈ 2.5 V, CAN Low ≈ 2.5 V (differential ~0 V idle)
- CAN dominant state: CANH ≈ 3.5 V, CANL ≈ 1.5 V (differential ≈ 2.0 V)
- Expected termination resistance: ~60 ohms measured between CAN H and CAN L with battery disconnected
- Battery supply to module: ~12–14.5 V with engine running or key on
- Ground resistance to chassis: low/near 0 ohms (verify continuity)
- LIN bus idle: pulled up to VBAT (approx battery voltage) and should show expected serial frames when active
Diagnostic algorithm
- Connect a professional scan tool and save all codes and freeze frame; note occurrence conditions and other U-codes.
- Identify which network (CAN, LIN, FlexRay) reported U2199 and list modules expected on that bus using wiring diagrams or OEM data.
- Perform a visual inspection of connectors, splice points, and harness along that network for damage, corrosion or aftermarket taps.
- With ignition ON, verify battery voltage and module power/ground at the suspect module connector pins; repair any power/ground faults.
- Check CAN bus health: measure CAN H and CAN L voltages with key ON and while cranking. Confirm termination by measuring resistance between CAN H and CAN L (~60 ohms).
- If possible, use a scope or data logger to view CAN differential signals for noise, missing recessive/dominant transitions, or bus flooding.
- Attempt to poll modules on the bus with the scan tool. If a single module causes bus off or flooding, disconnect that module and re-check bus communications.
- If a module is present but not responding, check for software updates or reflash possibilities per manufacturer procedures.
- If wiring and power/ground are good and the module still does not appear/respond, consider replacing the unresponsive module after verifying part/programming requirements.
- After repair, clear codes, perform relearn or reprogramming as required, and road test to confirm the fault does not return.
Likely causes
- Open or corroded connector or damaged wiring on the data bus
- Power/ground supply missing to the unknown module
- Short or open in CAN High or CAN Low wiring or poor termination
- Module not responding due to internal failure or not programmed
Fault status
Status
Lost communication with unknown control module — module not responding or not detected on network.
Repair difficulty: Medium
Diagnostic time: 1.5-3.0 hours
Similar codes
Workshop Manuals
Available brands with manuals
2
AUDI 11
6-speed manual gearbox 0B1, front-wheel drive — Workshop Manual (Edition 05.2014)
Workshop ManualAudi A3 (1997) – 1.6L 4-cylinder (2‑valve) Engine Mechanical Components Service Manual (AEH, AKL, APF) – Edition 07.2002
Workshop ManualAUDI A3 (2004) Workshop Manual — 2.0L FSI Turbo (4‑cyl, 4‑valve) Engine, Mechanics — Edition 03.2017
Workshop ManualAudi A3 2004 — Electrical System (Workshop Manual, Edition 02.2018)
Workshop ManualAudi A4 / A4 Cabriolet – 4.2 l V8 (5‑valve, timing chains) – Workshop Manual (Mechanics) – Edition 04.2007
Workshop ManualAudi A4 / A4 Cabriolet — Auxiliary Heater Workshop Manual (Edition 08.2004)
Workshop ManualAudi A4 / A4 Cabriolet (1.8T 4‑cyl turbo) — Motronic Injection & Ignition System Service Manual (Edition 01.2015)
Workshop ManualAudi A8 (2003) — Electrical System Workshop Manual (Edition 08.2014)
Workshop ManualAudi Q4 e-tron (Type F4) - Self-study Programme SSP 685
Workshop ManualAudi Q8 (2018) — Electrical System Workshop Manual (Edition 05.2019)
Workshop ManualAudi Servicing Manual — 7‑Speed Dual Clutch Transmission 0CJ / 0CL / 0CK / 0DN / 0DP / 0HL (Edition 05.2018)
Workshop ManualLAND ROVER 3
Land Rover Defender 300Tdi — Workshop Manual (1996 model year)
Workshop ManualLand Rover Defender Workshop Manual Supplement & Body Repair Manual (1999 & 2002 MY)
Workshop ManualLand Rover Range Rover — Electrical Library (LRL 0453ENG, 2002)
Workshop ManualYour experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email
Code
U2199
LAND ROVER
U — Network/User
Temperature data of invalid engine coolant
Views:
UK: 7
EN: 11
RU: 5
AI status
Completed
Completed
100%
Causes
- Disconnected or corroded connector for the unknown module
- Power or ground circuit fault to the module
- Damaged wiring harness or short on the vehicle communication bus (CAN/LIN)
- Missing or improperly configured module (aftermarket, removed, or not programmed)
- Faulty control module (internal failure)
- Bus wiring short to battery or ground or open circuit
Symptoms
- MIL or network-related warning lamps illuminated
- One or more vehicle systems inoperative or intermittent (depends on which module is missing)
- Other modules reporting multiple U-codes or network errors
- Inability of scan tool to identify a module or to communicate with all expected nodes
- Intermittent faults or faults present after recent wiring or module work
What to check
- Use a capable scan tool to read all stored U-codes and freeze frame data
- Perform a network node scan/discovery to list modules present on each bus
- Inspect connectors, pins and wiring for the suspected module/bus (corrosion, bent pins, disconnected plugs)
- Verify battery voltage and chassis/engine grounds at the module connector
- Measure CAN/LIN bus voltages with a multimeter or better with a lab scope
- Check termination resistor across CAN H and CAN L (~60 ohms total)
Signal parameters
- CAN bus idle voltages: CAN High ≈ 2.5 V, CAN Low ≈ 2.5 V (differential ~0 V idle)
- CAN dominant state: CANH ≈ 3.5 V, CANL ≈ 1.5 V (differential ≈ 2.0 V)
- Expected termination resistance: ~60 ohms measured between CAN H and CAN L with battery disconnected
- Battery supply to module: ~12–14.5 V with engine running or key on
- Ground resistance to chassis: low/near 0 ohms (verify continuity)
- LIN bus idle: pulled up to VBAT (approx battery voltage) and should show expected serial frames when active
Diagnostic algorithm
- Connect a professional scan tool and save all codes and freeze frame; note occurrence conditions and other U-codes.
- Identify which network (CAN, LIN, FlexRay) reported U2199 and list modules expected on that bus using wiring diagrams or OEM data.
- Perform a visual inspection of connectors, splice points, and harness along that network for damage, corrosion or aftermarket taps.
- With ignition ON, verify battery voltage and module power/ground at the suspect module connector pins; repair any power/ground faults.
- Check CAN bus health: measure CAN H and CAN L voltages with key ON and while cranking. Confirm termination by measuring resistance between CAN H and CAN L (~60 ohms).
- If possible, use a scope or data logger to view CAN differential signals for noise, missing recessive/dominant transitions, or bus flooding.
- Attempt to poll modules on the bus with the scan tool. If a single module causes bus off or flooding, disconnect that module and re-check bus communications.
- If a module is present but not responding, check for software updates or reflash possibilities per manufacturer procedures.
- If wiring and power/ground are good and the module still does not appear/respond, consider replacing the unresponsive module after verifying part/programming requirements.
- After repair, clear codes, perform relearn or reprogramming as required, and road test to confirm the fault does not return.
Likely causes
- Open or corroded connector or damaged wiring on the data bus
- Power/ground supply missing to the unknown module
- Short or open in CAN High or CAN Low wiring or poor termination
- Module not responding due to internal failure or not programmed
Fault status
Status
Lost communication with unknown control module — module not responding or not detected on network.
Repair difficulty: Medium
Diagnostic time: 1.5-3.0 hours
Similar codes
Workshop Manuals
Repair manuals for LAND ROVER
3
Land Rover Defender 300Tdi — Workshop Manual (1996 model year)
Workshop ManualLand Rover Defender Workshop Manual Supplement & Body Repair Manual (1999 & 2002 MY)
Workshop ManualLand Rover Range Rover — Electrical Library (LRL 0453ENG, 2002)
Workshop ManualYour experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email