U068C

Code

Generic U — Network/User

Lost Communication With Turbocharger/Supercharger Inlet Pressure Sensor B

Brand: Generic

Type: U — Network/User

Views: UK: 25 EN: 31 RU: 22

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Page language: EN

Causes

Damaged or disconnected sensor connector or wiring harness (open/short/intermittent)
Failed inlet pressure sensor (internal electronic failure)
Loss of sensor supply voltage or ground
CAN/LIN/serial bus fault, missing termination, or high bus error rate
Faulty gateway/module or ECU that reads the sensor data
Corroded pins or water intrusion at connectors

Symptoms

Malfunction Indicator Lamp (MIL) or network warning illuminated
Loss of boost pressure reading for sensor B in live data or frozen/stale values
Reduced engine performance, turbo control faults, or limp mode depending on vehicle strategy
Multiple network communication related DTCs present
Intermittent drivability issues tied to vibration or weather conditions

What to check

Read and record freeze frame and full DTC list; note if code is permanent or intermittent
Check for other network/U-codes that indicate a wider bus problem
Visually inspect sensor B connector, wiring harness and nearby components for damage, chafing, corrosion or water entry
Check fuses/relays feeding the sensor and gateway modules
With ignition ON (engine off) backprobe sensor connector: verify reference voltage, ground continuity and signal presence per vehicle specification
Scan for live data from both inlet pressure sensors (A and B) and monitor for updates, time stamps, or implausible/stuck values

Signal parameters

Typical sensor supply/reference: 5 V (check vehicle spec)
Typical sensor signal: ~0.5–4.5 V (0 kPa to max range) for analog sensors — smart sensors may use digital protocols (SENT/LIN/CAN)
CAN bus idle: CAN_H ≈ 2.5–3.5 V, CAN_L ≈ 1.5–2.5 V (differential ~0 V idle; differential ~2.5 V during dominant bit) — verify against vehicle spec
Expected sensor current draw: low, typically
Termination resistance across CAN_H and CAN_L at network level: ~60 ohms (two 120 ohm terminators in parallel)

Diagnostic algorithm

Retrieve all codes and live data; note if code is present only after certain conditions and if other U-codes exist.
Perform visual inspection of sensor B and associated harness for damage, corrosion or water ingress; repair any obvious defects.
Verify power and ground at the sensor connector with key ON: check reference voltage and ground continuity to chassis and ECU ground.
Check the sensor signal line: if analog, backprobe and observe signal with key ON and while cranking/idle to confirm changing voltage; if digital, observe protocol activity with a scope or appropriate bus tool.
Check CAN/LIN bus integrity: measure CAN_H/CAN_L idle voltages, check for short to battery/ground, and measure termination resistance.
Perform wiggle/stress test of harness and connector while monitoring live data to find intermittent opens or shorts.
If wiring and bus look good, swap sensor B with sensor A (if identical and practical) or replace sensor with known-good unit to confirm sensor failure.
Repair or replace faulty wiring, connector, fuse, or sensor as indicated. Reprogram or update module software if manufacturer bulletin advises.
Clear codes and perform functional test and road test to verify the fault does not return.
If fault persists after sensor/wiring replacement, investigate gateway/module or vehicle ECU as potential cause (advanced module diagnostics may be required).

Likely causes

Broken/shorted wiring or poor connector at sensor B
Failed inlet pressure sensor B (internal communications electronics)
CAN/LIN bus wiring fault, missing termination resistor, or bus short to battery/chassis
Faulty power/ground to the sensor (fuse, connector, or splice)

Fault status

⚠️ Status

Control module has lost or failed to receive valid communication or signal from Turbocharger/Supercharger Inlet Pressure Sensor B. Check sensor B, associated wiring/connectors, supply/ground and vehicle communication bus (CAN/LIN).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours