P0720 means the transmission control module is not receiving a proper signal from the output speed sensor. This sensor measures how fast the transmission output shaft rotates, which determines vehicle speed and helps the TCM calculate gear ratios and shift points.
DTC/P0720·Opel
P0720 on Opel: Causes, Symptoms and Fix Cost
Quick Answer
High SeverityNot safe to driveOpel
P0720 on a Opel means the transmission control module is not receiving a proper signal from the output speed sensor. This sensor measures how fast the transmission output shaft rotates, which determines vehicle speed and helps the TCM calculate gear ratios and shift points.
Repair cost on Opel€68 - €280
What does P0720 mean on a Opel?
Opel Astra
2004-2023The Astra H and J with the Aisin AF17/AF22 automatic transmission trigger P0720 due to the output speed sensor failing from heat exposure. The sensor is located at the bottom of the transmission and is easy to access. A straightforward and inexpensive repair on these models.
What causes P0720 on a Opel?
Beyond the generic causes listed on the main P0720 page, these are the Opel-specific patterns we see most often:
Opel AstraAF17/AF22 output speed sensor heat degradation
Opel AstraSensor connector corrosion from road spray
How to diagnose P0720 on a Opel with OBD2
Follow these steps to pinpoint the root cause of P0720:
- Check if the speedometer is working. A dead speedometer alongside P0720 strongly points to the output speed sensor, since both the transmission and instrument cluster rely on this signal.
- Locate the output speed sensor on the transmission housing (typically near the tail shaft or differential housing). Inspect the connector for corrosion, loose pins, or damage.
- Measure sensor resistance with a multimeter and compare to manufacturer specifications (typically 300-1200 ohms). Also check for signal voltage while spinning the sensor manually if accessible.
- Use a scanner to monitor live data and compare input speed versus output speed readings. The output speed should correlate with vehicle speed and the current gear ratio.
- If the sensor and wiring test normal, inspect the transmission fluid for metal contamination. Debris on the magnetic sensor tip can cause signal distortion.
How much does P0720 cost to fix on a Opel? (EUR)
Estimated repair costs on a Opel (Opel parts and labour typically run 20% below the average for this code).
Prices estimated as of May 2026. Costs vary by region, vehicle, and shop.
Related codes that often appear with P0720 on Opel
These codes commonly cluster with P0720 on Opel vehicles:
FAQ: P0720 on Opel
What does P0720 mean?
P0720 means the output speed sensor on your transmission is not sending a valid signal. This sensor measures how fast the output shaft spins, which tells the car its road speed and helps the transmission decide when to shift.
Can P0720 cause my speedometer to stop working?
Yes. Many vehicles use the output speed sensor signal for the speedometer. If the sensor fails, your speedometer may read zero or fluctuate wildly, and cruise control will stop working.
Is the output speed sensor easy to replace?
On most vehicles, yes. The sensor is externally mounted on the transmission case and can be replaced with basic tools. The part costs 25-120 EUR and replacement takes 30-60 minutes for a competent DIYer.
Can P0720 affect ABS and traction control?
Yes. The ABS and stability control systems use vehicle speed data. A faulty output speed sensor can trigger ABS and ESP warning lights because the system detects conflicting speed signals.
What is the difference between P0715 and P0720?
P0715 relates to the input (turbine) speed sensor at the front of the transmission, while P0720 relates to the output speed sensor at the rear. The input sensor measures engine-side speed, the output sensor measures wheel-side speed.
Looking for the full P0720 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0720 guideSkanyx · Opel
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