P0115Generic code

P0115 Code: Engine Coolant Temperature Circuit Malfunction

The P0115 code means there is an electrical fault in the ECT sensor circuit: the computer is getting an impossible signal or none at all. The usual culprits are a damaged connector, a cut wire or the sensor itself.

Severity
Medium
Can I keep driving?
Yes, but with caution
Estimated cost
$15 to $250
Difficulty
Easy
System
Air and Fuel
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0115 code means

The engine coolant temperature (ECT) sensor sits in the cylinder head or in the thermostat housing, in contact with the coolant. The computer relies on it because it decides cold enrichment, idle speed, when to enter closed loop, the radiator fan and, on automatic transmissions, torque converter lockup.

The computer watches to make sure the ECT signal always stays within the possible electrical limits. The P0115 code means it detected a fault in the circuit: the signal disappeared, went out of range, or does not correspond to any physically possible value. It is a generic code that some manufacturers use in place of the specific low and high signal codes.

Remember that the code points to the circuit where the computer saw the anomaly, not necessarily the failed part. Check the wiring before you replace the sensor, and test the ECT sensor step by step as described below.

P0115 code symptoms

  • Check engine light on steadily.
  • Radiator fan running continuously.
  • Erratic temperature gauge on vehicles where the dash uses this sensor.
  • Companion codes for the same sensor may appear (low signal, high signal or intermittent).

Likely causes of the P0115 code

  1. Damaged, loose or corroded connector, the most frequent cause.
  2. Wiring cut or shorted between the sensor and the computer.
  3. Failed sensor, open or shorted inside.
  4. Supply reference missing, 5 V or 12 V depending on the sensor design.
  5. Computer failure, very uncommon, so rule out everything above first.
  6. Complementary check: a low coolant level leaves the sensor surrounded by air and gives erratic readings, so top off and bleed the system before you diagnose.

How to diagnose the P0115 code step by step

  1. Read the sensor live data and compare it with what is expected. With a cold engine after a full night, the ECT should match the IAT. After starting, the temperature should climb steadily to 85 to 105 °C (185 to 221 °F).
  2. Inspect the connector. Unplug it, look for green, backed-out or oily pins, and plug it back in firmly.
  3. With the key on and the sensor unplugged, measure the reference at the connector. There should be about 5 V between the signal and ground.
  4. Jumper test. With the sensor unplugged, the scan tool should show about -40 °C (-40 °F). When you join the two connector pins with a wire, it should jump to more than 120 °C (248 °F). If it does, the wiring is fine and the problem is the sensor.
  5. Measure the sensor resistance and compare it with the technical data table at the current temperature.
  6. Do the wiggle test with the engine running. Move the harness and the connector while you watch the live data, because a jump shows you where the fault is.
  7. Check the continuity of each wire between the sensor connector and the computer connector with the key off.

How to fix the P0115 code

  • Repair the connector or the damaged wiring.
  • If the supply, ground and wiring are good, replace the sensor.
  • Clear the codes and check that they do not return.
  • Use a quality original or equivalent sensor, because cheap generic ones often have different response curves.
  • Clear the codes, drive one full cycle and check in live data that the reading makes sense.

Technical reference data

  • Approximate resistance: about 2,500 ohms at 20 °C (68 °F) and 200 to 300 ohms at 90 °C (194 °F).
  • Approximate signal voltage: 3 to 3.5 V cold and 0.5 to 1 V with the engine hot.
  • Normal operating temperature: 85 to 105 °C (185 to 221 °F).
  • Open circuit on the scan tool: about -40 °C (-40 °F). Short to ground: more than 130 °C (266 °F).
  • Values are approximate, so check the manufacturer data for your engine.

Brand-specific notes

Many engines have two sensors: one for the computer and one for the dash gauge. A gauge that reads correctly does not rule out an ECT fault, which is worth remembering with any P0115 code.

P0115 on Renault

On some Renault engines the sensor is dual, with two signals in one body.

P0115 on Peugeot

On some Peugeot engines the sensor is dual, with two signals in one body.

P0115 on Volkswagen

On some Volkswagen engines the sensor is dual, with two signals in one body.

Frequently asked questions about P0115

Can I drive with a P0115 code?
With caution and only for a short time. The engine runs on substitute values, so it may lose power or use more fuel and, in some cases, go into limp mode.
Does the P0115 code always mean replacing the ECT sensor?
No. In most cases the fault is in the connector or the wiring. Do the power, ground and continuity tests first.
What is the difference between low signal and high signal?
On a thermistor, a low signal means an impossibly high temperature (a short circuit) and a high signal means an impossibly low temperature (an open circuit).
How much does it cost to fix P0115?
Roughly $15 to $250. The cheapest repair is fixing a connector and the most expensive is replacing the sensor with labor. It varies by shop and region.
What does the P0115 code mean?
It is a generic OBD2 code that means the engine coolant temperature sensor circuit has an electrical fault. The computer sees a signal that is impossible or missing.
What is the most common cause of P0115?
A damaged, loose or corroded connector. A low coolant level can also give erratic readings, so top off and bleed the system before you diagnose.

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