C1278: Test mode: RL sensor interval
Short answer: C1278 means “Test mode: RL sensor interval”. Below is what it means on each of the 2 cars we cover, with a link to the full page for each car.
C1278 on each car
| Car | Meaning on this car | Confidence |
|---|---|---|
| Toyota Passo (1st gen) | Test mode: RL sensor interval (C1278/88) | high |
| Toyota Corolla (9th gen, E120) | Abnormal change in output voltage of left rear speed sensor (C1278/78) | high |
Symptoms
- Only in sensor test mode
Likely causes
- Test mode: RL sensor interval
What to check, in order
- Drive straight 4-7 km/h (electrical) or 10-40 km/h for >=5 s (interval) to clear
Causes and checks above are the general meaning. The exact test steps and values differ by car: open your car’s page.