DTC P0116: Engine Coolant Temperature (ECT) Sensor Performance Problem

1999 Saab 9-3 Base, 2D Hatchback, AutomaticSECTION DTC P0116: Engine Coolant Temperature (ECT) Sensor Performance Problem
NOTE: DTC P0116 indicates that ECT value received by ECM was compared to a calculated substitute value and found to be at least 68°F (20°C) below or 118°F (48°C) above normal range.
  1. Check coolant for proper level and concentration. Check thermostat operation and ensure that cooling system is working properly. If no cooling system problems were found, go to DTC P0117-P0118: ENGINE COOLANT TEMPERATURE (ECT) SENSOR CIRCUIT . If problems were found, repair cooling system. If referred here from DTC P0125, go to next step. Otherwise, go to step  3.
  2. Ensure that both intake air and coolant temperatures exceed 50°F (10°C). Start engine and allow it to idle for at least 4 minutes. Check scan tool display. If OK is displayed, use scan tool to clear all system DTCs. If NOT READY is displayed, back up to INITIATING DIAGNOSTICS on scan tool and retest. If DTC P0125 is still present, substitute known good ECM and retest system. See ENGINE CONTROL MODULE (ECM) under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION article.
  3. Measure external cylinder head temperature with a thermometer. Compare with temperature displayed on scan tool. Check readings when engine is both cold and hot. Readings should not vary more than 50°F (10°C). If readings are as specified, Clear all system DTCs. If readings are not as specified, problem is still present.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
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