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P1255 Code in 2001 VW Cabrio: Engine Coolant Temperature Sensor Short to Ground - Diagnosis & Repair Advice

Model: VW Cabrio Fault Code: P1255 Posted: 2006-08-28 08:21

My daughter drives a 2001 Volkswagen Cabrio with only 60,000 miles. The vehicle consistently displays the P1255 diagnostic trouble code — 'Engine Coolant Temperature Sensor Short to Ground'. I've reset this code three times in the past week, but it returns each time. I took the car to a local repair shop that charged $360 for replacing the mass air flow (MAF) sensor and spark plugs. They claimed these were the components associated with the P1255 code based on their scanner reading. However, after the replacement and reset, the engine still exhibits irregular behavior: it lurches during idle, produces a small surge followed by a clicking noise, and the P1255 light reappears. The driver reports that at times the engine idles as low as 300 RPM — nearly stalling — before recovering to around 900 RPM. On other occasions, the engine races briefly before settling back into idle. I've been unable to find a repair shop that charges less than $300 for such work. I recently purchased an Actron 9125 scanner and performed a resistance test on terminals 1 and 3 of the coolant temperature sensor as recommended in the Haynes Manual. The readings varied slightly when cold versus warm, but were not definitive. Given this behavior, I'm wondering: should I replace the engine coolant temperature sensor? Or could there be another underlying issue — such as a wiring fault or grounding problem — that I haven't identified? Any experience with P1255 on 2001 VW Cabrio models? What are common causes and proper diagnostic steps? Mark

Related fault codes

P1255

Comments (3)

Anonymous 2006-08-28 15:30

You're asking whether you're experiencing the same symptoms after the MAF replacement — did you know what the original code was before the repair shop worked on it? This is a critical detail. Many shops don't list the actual diagnostic trouble code on their invoices, and that can lead to incorrect diagnoses. It's possible your shop has an outdated scanner or misreads the code — for example, their reference book might list MAF as the issue while your manual points to the coolant sensor. If it were my car, I'd contact a Volkswagen dealership to confirm what P1255 actually means. Also, please verify that the coolant level is correct and that the rest of the cooling system (radiator, hoses, thermostat) is functioning properly. Best of luck — keep us updated! Jeff

Anonymous 2006-09-01 15:12

I recently checked the most up-to-date diagnostic codes from a trusted automotive resource and took my vehicle to an independent shop because the VW dealer is prohibitively expensive. I've found that while the car runs reasonably well, it still experiences occasional idle fluctuations — especially when idling at low speeds. The coolant level is correct, and there are no visible signs of overheating or cooling system failure. If these issues persist, my next step will be to visit a certified Volkswagen dealership for professional diagnosis and repair.

Anonymous 2006-09-01 15:59

Try unplugging the engine coolant temperature sensor and observing if the idle instability improves. This simple test can help determine whether the sensor itself is faulty or if the issue lies in wiring or grounding connections.