B1620: SRS Control Module Internal Fault

Usually a hardware fault

What B1620 means

The meaning of B1620 splits cleanly along brand lines. On Nissan and Infiniti, B1620 is defined as a supplemental restraint system control module internal fault, with the standard remedy being to replace the SRSCM. On those makes there is essentially one cause, an internal failure of the module itself. A short, an open, or another SRS component cannot set it. On Toyota and Scion, the same number reads as a side airbag sensor right circuit malfunction, which is a different animal entirely.

Because of that split, the first job is to confirm what you are driving before assuming what B1620 means. We see it most as a Nissan and Infiniti module-internal code.

Common causes

• On Nissan and Infiniti, an internal failure of the SRS control module
• Voltage problems from a weak battery, bad jump-start, or failing alternator corrupting the module self-test
• Corroded or loose wiring between a sensor and the module, which can mimic an internal fault
• On Toyota and Scion, a side airbag sensor circuit issue on the right side

Crash data or hardware fault?

Hardware, on both readings. On Nissan and Infiniti it is the module declaring itself faulty. On Toyota it is a sensor circuit. Both are live faults the repair has to address at the part, which is what sets B1620 apart from a stored crash code a reset clears. Before condemning the module, it is worth ruling out voltage and connection problems, since those can falsely trip a B1620 on the Nissan side.

Does our reset clear it?

Not by itself, when B1620 is a true internal module fault or a live sensor circuit fault. A reset clears stored data, while a failed part needs repair or replacement to clear for good. If you are on a Nissan or Infiniti and the module is the suspect, send it to us and we will test it and tell you whether it can be saved or needs replacing through our module service. If there is also stored crash data from a prior event, we clear that as part of the work.

Which makes throw it

B1620 appears on Nissan and Infiniti as a module-internal fault and on Toyota and Scion as a side sensor circuit. Same number, two meanings, so read it against the make.

What to do next

Confirm the make, then check battery voltage and module connectors first, because those are the cheap fixes that can mimic a dead module. If the module still fails, send it in. Related codes: B1015 (diagnosis sensor unit), B1000 (airbag ECU malfunction), and B1916 (airbag circuit fault).