P0116 - Engine Coolant Temperature Sensor (ECT) Sensor '1' Range/Performance
System
Powertrain (Engine & Gearbox)
Technical Description
The control module has detected a fault in the Engine Coolant Temperature Sensor (ECT) Sensor '1' Range/Performance (P0116). The reported signal is electrically valid but disagrees with other operating parameters (RPM, load, or other sensors). Pertains to upstream oxygen sensor (pre-catalyst regulation sensor) governing real-time closed-loop air-fuel ratio.
Multimeter Test Points & Nominal Values
| Test Point / Component | Measurement | Nominal Target Range | Test Condition |
|---|---|---|---|
| Engine Coolant Temperature Sensor (ECT) Sensor '1' Range/Performance – Resistance at 20 °C | Resistance (kΩ) | 2.0 - 3.0 kΩ | Sensor disconnected, cold engine |
| Engine Coolant Temperature Sensor (ECT) Sensor '1' Range/Performance – Resistance at 80 °C | Resistance (Ω) | 250 - 400 Ω | Sensor disconnected, at operating temp |
| Engine Coolant Temperature Sensor (ECT) Sensor '1' Range/Performance – Signal Voltage | Voltage (V) | 0.3 - 4.5 V (falls as temperature rises) | Ignition ON, sensor connected |
| 5 V Reference / Signal Ground | Voltage (V) | 4.95 - 5.05 V / < 0.05 V | At sensor connector |
Sensor disconnected, cold engine
Sensor disconnected, at operating temp
Ignition ON, sensor connected
At sensor connector
Oscilloscope Waveform Analysis
30 s/div, 1 V/divPossible Causes
Engine Coolant Temperature Sensor (ECT) Sensor '1' Range/Performance is electrically operational but performing outside calibrated tolerance
Sensor 1 (Upstream pre-cat):Directly exposed to raw exhaust gases. Check for carbon fouling or pre-sensor manifold exhaust leaks.
Chafed or pinched wiring harness along the signal path to Engine Coolant Temperature Sensor (ECT) Sensor '1' Range/Performance
Poor ground connection or excessive voltage drop (> 0.1 V) at the ground point for Engine Coolant Temperature Sensor (ECT) Sensor '1' Range/Performance
Defective internal output driver or reference circuit in the control module for Engine Coolant Temperature Sensor (ECT) Sensor '1' Range/Performance
Symptoms
5
Recommended Solution
Observe closed-loop sensor voltage switching at 2500 RPM (0.1–0.9 V at 1–3 Hz). Check STFT and LTFT fuel trims.
Log component live data across varying load points and verify plausibility against engine target model.
Verify loaded supply voltage and harness terminal pins at Engine Coolant Temperature Sensor (ECT) Sensor '1' Range/Performance.
Check circuit continuity and ground-side voltage drop (< 0.05 V) for Engine Coolant Temperature Sensor (ECT) Sensor '1' Range/Performance.
Replace the sensor if resistance is off-curve, otherwise repair wiring/connector.
Mechanic's Tip
Jumper the sensor connector and watch the scan tool: the value must peg to max temp instantly. Short it to ground and it must peg to min. If the value sweeps freely the sensor is at fault — otherwise the wiring or module is.
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