Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC P0116/16500 - ECT Sensor CKT Range/Performance Problem
1996 Audi A4 Base, StandardSECTION DTC P0116/16500 - ECT Sensor CKT Range/Performance Problem
NOTE:
DTC is set as soon as coolant temperature is less than 131°F (55°C) after engine start, but 18 minutes later temperature has not risen to more than 158°F (55°C).
- Inspect Engine Coolant Temperature (ECT) sensor connector for looseness and/or corrosion. Repair sensor connector as necessary. If sensor connector was not repaired, go to next step. If sensor connector was repaired, erase DTC memory and test drive vehicle.
- Turn ignition off. Disconnect ECT sensor connector. Using a DVOM, check resistance between ECT sensor terminals No. 1 (signal) and 3 (ground). See ECT SENSOR RESISTANCE table. If resistance is to specification, go to next step. If resistance is not to specification, replace ECT sensor. Erase DTC memory and test drive vehicle.ECT SENSOR RESISTANCE
Temperature Ohms 68°F (20°C) Approx. 2500 176°F (80°C) Approx. 330 - Turn ignition off. Disconnect Powertrain Control Module (PCM) connectors. Connect VAG 1598/19 test box to PCM wiring harness. Terminal assignments of test box are identical to PCM connectors "A", "B", "C", "D" and "E".
- Using DVOM, check resistance between ECT sensor connector terminal No. 3 and engine ground. Resistance should be a maximum of one ohm. If resistance reading is within specification, go to next step. If resistance reading is not within specification, repair open or short circuit between ECT sensor connector terminal No. 3 and engine ground. Erase DTC memory and test drive vehicle.
- Using DVOM, check resistance between ECT sensor connector terminal No. 1 and test box socket 16A. Resistance should be a maximum of one ohm. If resistance reading is within specification, go to next step. If resistance reading is not within specification, repair open or short circuit between ECT sensor connector terminal No. 1 and PCM connector "A" terminal No. 16. Erase DTC memory and test drive vehicle.
- Check ECT sensor connector terminals No. 1 and 3 for shorting to each other. If circuits are shorting to each other, repair as necessary. Erase DTC memory and test drive vehicle. If circuits are not shorting to each other, replace faulty PCM. Code new PCM and test drive vehicle. See PCM CODING in this article.
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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.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.