P0116

Engine Coolant Temperature Sensor Circuit 1 Range/Performance Problem

P0116 is a generic OBD-II powertrain diagnostic trouble code: Engine Coolant Temperature Sensor Circuit 1 Range/Performance Problem. It is logged by the engine control unit when the coolant monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P0116
Group
Powertrain
System
Coolant
Severity
moderate
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What P0116 means

P0116 is a performance code set when the powertrain control module (PCM) detects that the Engine Coolant Temperature (ECT) sensor's output signal is implausible, erratic, or inconsistent with expected engine behaviour during a warm-up cycle. The ECT sensor is a critical NTC thermistor: at low temperatures its resistance is high (producing a high voltage at the PCM input), and as the engine warms up the resistance drops, pulling the signal voltage toward 0.5 V. The PCM expects a smooth, monotonic rise in temperature from cold start to the thermostat's opening point; any sudden jumps, flat-line readings, or values that conflict with intake air temperature or run-time data will trigger P0116.

The ECT sensor directly influences fuel injection quantity and timing, idle speed, fan control, EGR operation, and transmission shift points. A faulty sensor reading can therefore cause excessive fuel consumption (the PCM believes the engine is perpetually cold and enriches the mixture), overheating (the cooling fan does not activate correctly), poor idle quality, and rough shifts in automatic transmission vehicles.

A particularly insidious failure mode is an intermittent open circuit caused by connector corrosion — the sensor reads plausibly at rest but drops out momentarily under vibration or thermal expansion, causing the PCM to see a sudden, impossible temperature jump. This type of fault is often only reproduced by wiggling the connector while monitoring live data. Coolant leaks that expose the sensor tip to air rather than liquid coolant can produce similar erratic behaviour.

P0116 should be distinguished from P0117 (signal low) and P0118 (signal high), which indicate fixed out-of-range voltages rather than dynamic performance issues. On vehicles with two coolant temperature sensors (some diesel engines and hybrids), verify which sensor — sensor 1 (primary, near thermostat) or sensor 2 (downstream) — the code refers to before starting diagnosis.

Common causes

Most-frequently reported root causes when P0116 is logged.

  • 1
    Faulty ECT sensor (internal thermistor degradation or sticking)
  • 2
    Corroded, damaged, or intermittent ECT sensor connector
  • 3
    Low coolant level causing the sensor tip to contact air rather than coolant
  • 4
    Cooling system air pockets trapping the sensor
  • 5
    Stuck-open or stuck-closed thermostat (engine never reaches or exceeds normal temp)
  • 6
    Damaged or open-circuit signal or ground wire to the sensor
  • 7
    Engine overheating causing sensor to briefly exceed its measurement range
  • 8
    PCM fault or damaged analog input circuit

Symptoms drivers notice

MIL (check engine light) illuminated
Erratic or incorrect coolant temperature gauge reading
Hard or extended cold starts
Excessive fuel consumption (engine runs in cold-start enrichment for too long)
Rough idle during warm-up
Cooling fan activating incorrectly (too early, too late, or not at all)
Automatic transmission harsh or delayed shifts

How to diagnose P0116

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool and observe live ECT sensor voltage during a cold-start warm-up; the voltage should decrease smoothly from approximately 3.5–4.5 V cold to 0.5–0.8 V at normal operating temperature
  2. 2
    Compare the ECT reading against intake air temperature at cold start — on a fully cold engine they should be within 5 °C of each other
  3. 3
    Check the coolant level; a low system can expose the sensor tip to air and produce erratic readings
  4. 4
    Inspect the ECT sensor connector for corrosion, moisture, or damaged pins; wiggle the harness while monitoring live ECT data to detect intermittent open circuits
  5. 5
    With the sensor disconnected, measure resistance across the sensor terminals and compare to the manufacturer's temperature-resistance chart — a sticking or open reading indicates sensor failure
  6. 6
    Verify thermostat operation: if the engine reaches normal temperature on the gauge but the ECT sensor voltage stays high (reading cold), the sensor is faulty; if the engine genuinely runs cold, the thermostat may be stuck open
  7. 7
    Clear the code and perform a full warm-up drive cycle; if P0116 returns after sensor and wiring checks pass, investigate the cooling system for air locks or thermostat failure

Vehicles where we've handled P0116

Platforms in our catalogue with confirmed P0116 coverage.

AUDI A6
2015
AUDI A7 30D
AUDI A6 30D
2015
AUDI A7

Related powertrain codes

Frequently asked questions

Is P0116 dangerous to drive with?

Potentially. If the sensor is reading colder than actual, the PCM may not activate the cooling fan promptly, risking genuine overheating. Watch the temperature gauge independently and do not ignore rising temperatures while the fault is present.

Can a stuck thermostat cause P0116?

Yes. A thermostat stuck open will prevent the engine from reaching normal operating temperature. The PCM expects the ECT to reach a threshold within a defined time; if it never does, P0116 can set even if the sensor itself is perfect.

Why is my coolant gauge showing normal but I still have P0116?

The dashboard gauge is often driven by a separate sender unit, not the ECT sensor the PCM uses. A faulty ECT sensor can feed incorrect data to the PCM while the gauge sender reads correctly, explaining why the gauge looks normal but the code is present.

How is P0116 different from P0117 or P0118?

P0117 and P0118 flag a fixed, static out-of-range voltage (always too low or always too high). P0116 fires when the signal is within the voltage range but behaves erratically or implausibly — for example, changing too quickly or not changing at all during a warm-up cycle.

Can air in the cooling system cause P0116?

Yes. Air trapped at the ECT sensor location will cause the sensor to measure air temperature instead of coolant temperature, producing erratic or unrealistically low readings. Bleeding the cooling system properly after coolant changes or repairs can resolve the fault without replacing any parts.

Disabling P0116 in software

RaceTune can permanently disable P0116 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

ECUs with a P0116 disable in our catalogue

Confirmed coverage from our recipe database — we support many more families. Upload your file and our identifier will match it automatically.

  • Bosch EDC17CP44 verified 1 software version

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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