S7-400 Cpu 414-4h - REDF led is permanantly on as well as BUS1F is blinking continously

Hello Saqib;

Whenever the CPU's OS detects an event that affects the running of the system, it activatess the diagnostic LEDs implicated and  it logs messages in the diagnostic buffer that you can use to determine the cause of the problem.

Connect to one of the CPUs, open the diagnostic buffer of the CPU (CTRL+D in Simatic Manager) use the Save AS button on the diagnostic buffer page to create a text file (opens with Notepad) containing the logged messages.

Do the same on the second CPU, so you can compare the buffer contents.

If you have trouble understanding the messages, attach the text files here so we can help you understand them and search for a solution.

Hope this helps,

Daniel Chartier

Hello saquib;

Both the types of messages linked to OB 122 (I/O Access Error) in your diagnostics buffer messages and the comibination of the active LEDs point to one (or more) DP slave not responding on your MPI/DP port (BUSF1). See the attachment below, taken from the following manual (which I recommend you study when working with fault-tolerants Systems; this is from section 5.2):

Simatic Fault Tolerant Systems S7-400H :

https://support.industry.siemens.com/cs/ww/en/view/82478488

The faults relevant to OB 121  (Programming error: Timer number error) I have not seen before; it may be resolved along with the redundancy error linked to the REDF LED when you correct the Profibus-DP connectoion to the failing slaves.

The easiest way to locate the faulty slaves is to open the HWConfig editor, and then go ONLINE (click on the glasses icon in the menu bar). In that view, failing nodes are identified with a red cross icon, meaning failure. if you double click on the identified slaves, you will open the diagnostic buffer for ghe slaves and the messages logged there can help you understand the cause of the problem locally.

Hope this helps,

Daniel Chartier