17664 on 1996-2001 Audi A4 — Engine Coolant Temperature Circuit (G62): Open / Short to B+
1 vehicles · 1 makes · $30-$180 repair
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Audi A4 · 1996–2001
The original black-housing dual coolant temperature sensor (G62) mounted in the coolant flange at the back of the cylinder head develops cracks and fails internally. The temperature sensor G2 (also known as G62) for the gauge has likely failed and is relatively easy to fix; it is located in the coolant flange at the back of the cylinder head and the early square-connector style and later elongated D-shaped black connector sensors are known problematic units. When it fails the ECU sees an implausible coolant temperature, leading to cold starting difficulties at low temperatures, poor idle and acceleration during warm up as well as an erratic or dead temperature gauge.
Common Symptoms
- erratic or dead coolant temperature gauge
- hard cold starts
- rough idle during warm-up
- poor fuel economy
- rich-running condition
- check engine light
How to Fix
Scan with VAG-COM/VCDS for fault 17664 / 16502 (P0118) and bench-test the sensor's resistance. From Bentley, the G62 test procedure: allow engine to cool to room temp (68F/20C), disconnect ECT sensor, connect multimeter to terminals 1 and 2; resistance must be 1500 to 3000 ohms — if not, replace the ECT. Replace with the updated green-top OEM sensor (part 059 919 501A) along with the retaining clip (032 121 142) and O-ring; replacing this sensor resolves running issues for many owners who are still using the original black sensor which had a high failure rate. Part is ~$25-40, DIY 30 minutes; shop labor brings total to ~$80-180.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Engine Coolant Temperature SensorCross-refTSE 1D
Fitment confirmed against the ShowMeTheParts catalog for this vehicle's year and engine.
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Sources for this issue (1)
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17664 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does 17664 mean?
17664 stands for "Engine Coolant Temperature Circuit (G62): Open / Short to B+." This VAG-specific fault code (OBD-II equivalent P1256) indicates the engine control module has detected an electrical fault in the Engine Coolant Temperature Sensor (G62) circuit — either an open circuit or a short to positive (B+). Because the ECM relies on coolant temperature to manage fuel delivery, ignition timing, and glow plug operation, a bad signal causes the engine to run on incorrect temperature data. Common symptoms include hard cold starts, high or irregular idle (1200–3000 RPM), poor warm-up acceleration, and erratic temperature gauge behavior.
What are the most common causes of 17664?
The most common causes of 17664 are: Faulty Engine Coolant Temperature Sensor (G62) — original black sensors on 1995–2002 VWs are a known failure point, replaced by green units, Open or broken wiring between the sensor and the ECM, Short to positive (B+) in the sensor wiring, Corroded, loose, or damaged sensor connector, Wiring harness chafing or insulation damage near the sensor. The specific cause varies by vehicle.
How much does it cost to fix 17664?
Repair costs for 17664 range from $30 to $180, depending on the vehicle and root cause.
Which vehicles are affected by 17664?
Au7o has documented 17664 across 1 vehicle models from 1 manufacturers: Audi.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.