Fault 12 Code 170 — System configuration, ISM1 not detected

What does Fault 12 170 mean?

The Worcester Bosch Greenstar CDi Boiler displays Fault 12 with code 170, indicating a system configuration issue where ISM1 (Internal System Module 1) is not detected by the controller.

• ISM1 connection is loose or faulty
• ISM1 module is not powered or has failed

Click steps to track your progress.

1. 1

   Visually check the physical connection cable to ISM1 for any damage or looseness.

2. 2

   Ensure ISM1 is receiving power and is properly seated.

3. 3

   If the connection seems correct, contact a qualified heating engineer to inspect ISM1 or its wiring.