SRS Control

The SRS system is composed of highly complex systems with a number of components that require exact replacement and testing procedures. One of the elements is a SRS module which is considered a "One Time Use Component" when a car is in an accident the module stores a crash code and it needs to be replaced in order to activate the airbags again.

  • Test terminal or SRS warning light lead is shorted to battery + or to ground. Symptom: warning light continuously on or always off.
  • BOTH seat belt tensioners disconnected (no code if only one connected
  • Fault in crash sensor
  • Fault in standby power unit or in wiring between unit and sensor
  • Air bag assembly resistance low
  • Air bag assembly resistance high
  • Air bag assembly shorted to ground
  • Mercury switch in sensor shorted, or closed for more than one minute. Lead to seat belt tensioner shorted to ground or battery positive.

SRS Cautions

  • Before touching your SRS system or any of its components, be sure you know what you are doing by reading the OEM SRS manual.
  • In addition, switch the ignition "off" and disconnect the battery negative lead before doing any work on the system.
  • Do not pound or tap anywhere near the SRS crash sensor (for example, while under the car) if the ignition is "on" even if you are not working on the SRS system.
  • Do not under any circumstance use an ohmmeter or live electrical measurement instrument to measure resistance in the airbag/seat tensioner or wiring while these components are connected, as this may cause them to activate.
  • You are highly advised to leave any repairs to trained HICLASS Electronics personnel who know what they are doing.


  • To avoid rendering the SRS inoperative, which could increase the risk of personal injury in the event of a collision which would result in air bag inflation, all maintenance must be performed by an authorized specialists.
  • Improper maintenance, including incorrect removal and installation of the SRS, can lead to personal injury caused by unintentional activation of the system.

One of the most complex systems in vehicles manufactured after 1990 is the Supplemental Restraint System, or SRS, commonly referred to as the airbag. The SRS is comprised of several components that must be replaced and tested according to exact standards. One such component is the SRS Module: after an accident, a crash code is stored within the module, requiring that the entire component be replaced so that the airbags can be reactivated.

There are a number of reasons that the SRS can malfunction in the absence of an accident:

  • Resistance too low/high for the airbag assembly
  • Crash sensor fault
  • Standby power unit fault
  • Fault in the wiring between the sensor and the unit
  • Short in the sensor's mercury switch, or switch closed for longer than 60 seconds
  • Short in lead to seat belt tensioner (to battery positive or ground)
  • Disconnect in front seat belt tensioners (will only code if both are disconnected)
  • SRS warning light lead or test terminal shorting to ground or to battery positive. (In this case, the warning light will be always off or continuously on.) Precautions for Working with the SRS
  • Read the manufacturer's SRS manual prior to any contact with the SRS system or its components.
  • Make sure that the ignition is in the "off" position, along with disconnecting the battery negative lead.
  • No contact should be made in close proximity to the SRS crash sensor (e.g. while working under the car) when the ignition is in the "on" position, whether or not you are actually working on the SRS system.
  • Under no circumstance should you use a live electrical measurement instrument (e.g. an ohmmeter) while the airbag/seat tensioner are connected. If you attempt to measure the resistance in those components or their wiring while they are connected, you may activate them!
  • It is strongly recommended that you consult with a HICLASS Electronics technician rather than attempting any SRS repairs yourself.


If SRS repairs are not performed by a trained specialist, the system may be left inoperable. In other words, you may disable the airbags completely, increasing the risk of injury and/or death in an accident.

Additionally, any maintenance or repair on the SRS that is done incorrectly can cause the system to activate, potentially leading to injuries due to unintentional airbag deployment.