Code
U0243
Generic
U — Network/User
Lost Communication With Parking Assist Control Module B
Views:
UK: 21
EN: 33
RU: 27
AI status
Completed
Completed
100%
Causes
- Faulty or unpowered Parking Assist Control Module B
- Open, shorted, or high-resistance wiring or damaged connector to the module
- Blown fuse or faulty power/ground to the module
- CAN bus wiring fault (short to voltage/ground or open circuit)
- Missing or failed termination resistor on the CAN bus
- Another module holding the bus off or causing heavy bus traffic/errors
Symptoms
- Dash message or lamp: Parking Assist Unavailable / Service Parking Assist
- No audible beeps or visual distance guidance from parking sensors
- Parking assist buttons disabled or non-responsive
- Related driver aids (cross-traffic alert, park assist) may be limited or inoperative
- Multiple network communication DTCs present on scan tool
What to check
- Connect a capable scan tool; read all U-codes and freeze-frame data, note any related module codes
- Verify battery voltage stable (12.4–13.0 V engine off, ~13.5–14.5 V charging with engine running)
- Visually inspect connectors and wiring at Parking Assist Control Module B for damage, corrosion, or water intrusion
- Check fuses/relays that supply the parking assist module
- Using a multimeter/oscilloscope, measure CAN_H and CAN_L voltages at the module connector with ignition ON and engine running
- Measure resistance between CAN_H and CAN_L with ignition off to verify ~60 ohms (two 120-ohm terminations in parallel) across the bus
Signal parameters
- CAN bus recessive state: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (both lines near mid-rail)
- CAN bus dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
- Typical termination: ≈ 60 ohms measured across CAN_H and CAN_L (two 120-ohm terminators in parallel)
- Common data rates: 250 kbps or 500 kbps for vehicle CAN networks (verify vehicle-specific rate)
- Expected: periodic messages from parking assist module when active; absence of messages suggests module offline or bus fault
Diagnostic algorithm
- Record all DTCs and vehicle conditions (freeze frame). Note if codes are permanent or intermittent.
- Attempt to communicate with Parking Assist Control Module B with a factory-level or bi-directional scan tool. If the module responds, check software/version; update if required.
- If the module does not respond, inspect and verify module power and ground circuits (battery voltage at power pin,
- Visually inspect module connector and harness for bent pins, corrosion, water intrusion, chaffing, or recent repair points. Repair connector faults as needed.
- Measure CAN_H and CAN_L at the module connector with key ON: verify recessive voltages ~2.5 V and dominant swings when bus is active. If voltages are out of range, trace wiring for short to battery or ground.
- With ignition off, measure resistance across CAN_H and CAN_L at multiple points to confirm proper termination (~60 ohms). Remove modules or connectors as needed to isolate an intermittent termination fault.
- Isolate the network segment: disconnect suspected modules one at a time (or remove connectors downstream) to locate source of bus fault. Observe when communication returns or codes clear.
- If wiring and bus are good but module still does not communicate, consider reprogramming or replacement of the parking assist module per manufacturer procedures. After replacement, ensure module is configured and coded to the vehicle.
- After repairs, clear codes and validate repair by exercising parking assist functions and re-scanning; road test and monitor for reappearance of the code.
Likely causes
- Disconnected/damaged connector or corroded pins at the parking assist module
- Loss of module power or ground (fuse/relay/harness issue)
- CAN_H/CAN_L short, open, or incorrect termination in the network segment
- Failed parking assist control module
- A different control module on the same CAN segment pulling the network down
Fault status
Status
Lost Communication With Parking Assist Control Module B — Parking assist functions may be disabled.
Repair difficulty: Medium
Diagnostic time: 1.0-3.5 hours
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Code
U0243
HYUNDAI
U — Network/User
Lost Communication With Parking Assist Control Module “B”
Views:
UK: 18
EN: 27
RU: 21
AI status
Completed
Completed
100%
Causes
- Faulty or unpowered Parking Assist Control Module B
- Open, shorted, or high-resistance wiring or damaged connector to the module
- Blown fuse or faulty power/ground to the module
- CAN bus wiring fault (short to voltage/ground or open circuit)
- Missing or failed termination resistor on the CAN bus
- Another module holding the bus off or causing heavy bus traffic/errors
Symptoms
- Dash message or lamp: Parking Assist Unavailable / Service Parking Assist
- No audible beeps or visual distance guidance from parking sensors
- Parking assist buttons disabled or non-responsive
- Related driver aids (cross-traffic alert, park assist) may be limited or inoperative
- Multiple network communication DTCs present on scan tool
What to check
- Connect a capable scan tool; read all U-codes and freeze-frame data, note any related module codes
- Verify battery voltage stable (12.4–13.0 V engine off, ~13.5–14.5 V charging with engine running)
- Visually inspect connectors and wiring at Parking Assist Control Module B for damage, corrosion, or water intrusion
- Check fuses/relays that supply the parking assist module
- Using a multimeter/oscilloscope, measure CAN_H and CAN_L voltages at the module connector with ignition ON and engine running
- Measure resistance between CAN_H and CAN_L with ignition off to verify ~60 ohms (two 120-ohm terminations in parallel) across the bus
Signal parameters
- CAN bus recessive state: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (both lines near mid-rail)
- CAN bus dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
- Typical termination: ≈ 60 ohms measured across CAN_H and CAN_L (two 120-ohm terminators in parallel)
- Common data rates: 250 kbps or 500 kbps for vehicle CAN networks (verify vehicle-specific rate)
- Expected: periodic messages from parking assist module when active; absence of messages suggests module offline or bus fault
Diagnostic algorithm
- Record all DTCs and vehicle conditions (freeze frame). Note if codes are permanent or intermittent.
- Attempt to communicate with Parking Assist Control Module B with a factory-level or bi-directional scan tool. If the module responds, check software/version; update if required.
- If the module does not respond, inspect and verify module power and ground circuits (battery voltage at power pin,
- Visually inspect module connector and harness for bent pins, corrosion, water intrusion, chaffing, or recent repair points. Repair connector faults as needed.
- Measure CAN_H and CAN_L at the module connector with key ON: verify recessive voltages ~2.5 V and dominant swings when bus is active. If voltages are out of range, trace wiring for short to battery or ground.
- With ignition off, measure resistance across CAN_H and CAN_L at multiple points to confirm proper termination (~60 ohms). Remove modules or connectors as needed to isolate an intermittent termination fault.
- Isolate the network segment: disconnect suspected modules one at a time (or remove connectors downstream) to locate source of bus fault. Observe when communication returns or codes clear.
- If wiring and bus are good but module still does not communicate, consider reprogramming or replacement of the parking assist module per manufacturer procedures. After replacement, ensure module is configured and coded to the vehicle.
- After repairs, clear codes and validate repair by exercising parking assist functions and re-scanning; road test and monitor for reappearance of the code.
Likely causes
- Disconnected/damaged connector or corroded pins at the parking assist module
- Loss of module power or ground (fuse/relay/harness issue)
- CAN_H/CAN_L short, open, or incorrect termination in the network segment
- Failed parking assist control module
- A different control module on the same CAN segment pulling the network down
Fault status
Status
Lost Communication With Parking Assist Control Module B — Parking assist functions may be disabled.
Repair difficulty: Medium
Diagnostic time: 1.0-3.5 hours
Similar codes
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