U068A

Code

Generic U — Network/User

Lost Communication With Barometric Pressure Sensor C

Brand: Generic

Type: U — Network/User

Views: UK: 21 EN: 32 RU: 23

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Page language: EN

MIL (Check Engine Light) or warning lamp illuminated
Stored U068A (and possibly related communication or sensor codes)
Engine may use default barometric pressure value causing rough idle, poor fuel trim or reduced performance
Hard starting or extended crank time in some conditions
Related sensors/ECUs may show no data for BARO C on a scan tool

Read and record scan tool data: confirm U068A and note freeze frame and accompanying codes
Check for additional communication codes (U0100, U0121, etc.)
Visually inspect sensor C connector and wiring for damage, corrosion, insulation wear, or water intrusion
Verify battery voltage and engine ground connections
Backprobe sensor connector to verify supply voltage and ground
Using scan tool, check whether BARO C data is present, updating and within plausible range

Analog sensors typically output ~0.5–4.5 V proportional to pressure
Expected barometric pressure range ~300–1100 mbar (hPa); typical engine bay values ~900–1050 mbar at sea level
Digital sensors may transmit on CAN/LIN/SPI/I2C — periodic update typically 1–10 Hz (varies by manufacturer)
Reference supply 5 V or 3.3 V depending on vehicle; ground reference required
Idle/default value may appear in PID if sensor communication lost

Connect a scan tool and read all stored and pending codes; record freeze frame and live BARO C PID if present.
Check for related communication codes (U0100, U0121, etc.) to determine scope of communication loss.
Inspect sensor C connector and wiring for corrosion, bent pins, water, or damage; repair as needed.
With ignition on, backprobe the sensor connector: verify supply voltage (battery or 3.3/5 V reference) and good ground. Replace or repair wiring if supply/ground missing.
If analog: measure sensor output voltage while varying engine load/altitude (or blow/suck on intake where applicable) to see if voltage changes plausibly.
If digital: use a scope or CAN/LIN bus tool to confirm the sensor’s message on the bus and check bus voltages (CANH/CANL idle ~2.5 V). Look for missing or corrupted messages.
Perform a wiggle test on wiring while monitoring live data to find intermittent faults.
Check continuity/resistance from sensor connector to control module connector; repair any opens/shorts.
Inspect and test related fuses and relays; confirm proper module wake-up and power sequencing.
If wiring and power are good but no communication from the sensor, substitute a known-good sensor (if available) or replace the sensor.
After repair, clear codes, perform a road test and re-scan to ensure code does not return. If problem persists and wiring is good, consider module/gateway fault and consult manufacturer resources for reflash or replacement.