U0611

Code

Generic U — Network/User

Lost Communication With Intake Air Temperature Sensor 1 Bank 1

Brand: Generic

Type: U — Network/User

Views: UK: 30 EN: 174 RU: 27

AI status

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Page language: EN

Causes

Open or short in IAT sensor wiring (signal, reference or ground)
Corroded, loose or damaged connector at the sensor or PCM
Failed IAT sensor (thermistor or integrated module)
Shared-sensor failure (IAT integrated in MAF or intake module)
Missing reference voltage or ground from PCM
CAN or LIN bus physical-layer fault (if the sensor reports digitally)

Symptoms

MIL / Check Engine Light ON with U0611 stored
No or invalid IAT PID reading on a scan tool (flatlined, erratic, or ‘‘no data’’)
Poor driveability (incorrect fueling/idle) when PCM lacks air temperature input
Reduced fuel economy or unstable idle under certain conditions
Related codes present (other sensor communication or network codes)
Cold/hot start performance affected if PCM uses IAT for enrichment

What to check

Connect a capable scan tool; record freeze frame data and live IAT PID behavior
Check for additional U- or P-codes that indicate wiring or module issues
Visually inspect sensor, connector, and wiring for damage, corrosion, heat or oil contamination
Verify connector pins are straight, clean and fully seated
With ignition ON (engine off) backprobe the sensor connector: check for reference voltage (if present) and ground
Measure IAT signal voltage while varying intake air temperature (blowing cold air or warming sensor) and note changes

Signal parameters

Typical IAT thermistor behavior: resistance decreases as temperature increases (NTC). Example reference values (vary by part): ~200–300 ohms at high temperatures (~100°C), ~2–3 kohm at ~20–25°C, and >50–100 kohm at very low temperatures (−40°C). Use OEM chart for exact values.
Expected sensor voltage (analog thermistor output to PCM) typically ranges ~0.1–4.8 V depending on air temperature; ~2.0–3.0 V near ambient is common. Values must change as temperature changes.
If IAT is integrated in MAF: the combined MAF/IAT sensor will show correlated changes in MAF frequency/voltage and IAT voltage/PID.
If the IAT is reported digitally (LIN/CAN): check message frequency and payload in manufacturer documentation. CAN physical-layer idle voltages: CAN_H ≈ 2.5–3.5 V, CAN_L ≈ 1.5–2.5 V (recessive); dominant states move ~1–2 V from idle. LIN idle ≈ battery voltage on master, data pulses to ground. Verify bus voltages/termination with oscilloscope or appropriate diagnostic tool.

Diagnostic algorithm

Retrieve all codes and freeze-frame data with a scan tool. Note IAT PID value and whether it updates. Check for other network codes.
Visually inspect sensor, wiring, and connector for damage, corrosion, or contamination. Repair visible damage.
With ignition ON (engine off), backprobe the sensor connector: verify presence of reference voltage (if applicable), signal voltage, and good ground. Compare to expected ranges.
Gently change intake temperature (blow cool air from a canned duster inverted or warm with a heat source held safely) while watching PID/signal voltage — a working thermistor will change smoothly.
Measure sensor resistance with connector disconnected (engine cold): compare to OEM resistance-vs-temperature chart. If resistance doesn't change with temperature or is outside expected range, suspect the sensor.
Perform continuity/resistance checks between sensor pins and PCM pins (engine off) to detect opens/shorts/high resistance. Check for short to battery or ground.
If the sensor is on a data bus: check CAN/LIN physical layer — measure CAN_H and CAN_L idle voltages, check termination resistors, and look for other modules reporting errors. Use oscilloscope to view message frames if available.
Wiggle harness and connectors while monitoring live data to catch intermittent failures.
If wiring, connector, or sensor repairs are made, clear codes and perform test drive to confirm code does not return.
If wiring and sensor check good, consider PCM/module communication fault; verify software level and consult manufacturer guidance before replacing modules.