Component Tests and General Diagnostics

Checking the supply voltage/ground terminal

Checking the power supply and ground terminals

Power supply, supplemental restraint system module (SRS)
The supplemental restraint system module (SRS) is powered via two power inputs.
When the ignition is switched on, at least one of the power inputs is powered and the supplemental restraint system module (SRS) is in active mode.
1. Power input 1 (comfort supply) is powered via a fuse and a relay (the comfort relay) from the central electronic module (CEM) in ignition positions I, II and III. This power input is used to power the supplemental restraint system module (SRS). The central electronic module (CEM) is powered from the battery via the integrated relay/fusebox in the engine compartment
2. Power input 2 (15-supply) is powered via a fuse from the ignition switch in ignition positions I and II. This power input is used to power the supplemental restraint system module (SRS). The ignition switch is powered from the battery via the integrated relay/fusebox in the engine compartment
3. The two independent power supplies are used to facilitate supply of power to the supplemental restraint system module (SRS) for longer in the event of a collision. In the event of simultaneous open-circuits in both power supplies, the supplemental restraint system module (SRS) will not be active.

Checking the power supply
Check the power supply cable from the battery, via the integrated relay/fusebox in the engine compartment, to the ignition switch. Check for and open-circuit. Check for loose connections. Check for contact resistance. Check for oxidation. Check the fuse.
Check the power supply cable from the battery, via the integrated relay/fusebox in the engine compartment, to the central electronic module (CEM). Check for and open-circuit. Check for a short-circuit. Check for contact resistance. Check for oxidation. Check for loose connections. Also check the fuse
Check the cable between:
- The integrated relay/fusebox in the engine compartment
- The integrated relay/fusebox in the engine compartment and the ignition switch
- The integrated relay/fusebox in the engine compartment and the central electronic module (CEM).
For further information about fault-tracing the power supply to the central electronic module (CEM), see central electronic module (CEM).
Remedy as necessary.
Check the power supply cable from the central electronic module (CEM), via the comfort relay, to power input 1 (comfort supply) on the supplemental restraint system module (SRS). Check for an open-circuit. Check for a short-circuit. Check for contact resistance. Check for oxidation. Check for loose connections. Also check the relay and the fuse.
Check the cable between:
- The central electronic module (CEM) and the comfort supply for the supplemental restraint system module (SRS).
Remedy as necessary.
Check the power supply from the ignition switch to power input 2 (15-supply) on the supplemental restraint system module (SRS). Check for an open-circuit. Check for a short-circuit. Check for contact resistance. Check for oxidation. Check for loose connections. Check the fuse.
Check the cable between:
- The ignition switch and the 15-supply for the supplemental restraint system module (SRS).
Remedy as necessary.

Ground terminal, supplemental restraint system module (SRS)
The supplemental restraint system module (SRS) is grounded when it is screwed into place in the car.

Checking the ground terminal
Check the ground connection between the supplemental restraint system module (SRS) and the ground terminal for resistance. With the ignition off and the supplemental restraint system module (SRS) installed, the resistance measurement between the supplemental restraint system module (SRS) and the ground terminal must be approximately 0 ohms.
Take readings between:
- The metal plate for the supplemental restraint system module (SRS) and ground terminal.
Remedy as necessary.

Caution! Do not touch the terminal pins in the supplemental restraint system module (SRS) and the central electronic module (CEM). There is a risk of static discharge which could damage the control modules.

Other information
- Connecting the breakout box Connecting the Breakout Box, Supplemental Restraint System Module (SRS)
- Signal specification Signal Specification
- For further information about cable routing and terminals, see the wiring diagram
- To access or replace the supplemental restraint system module (SRS) and the connectors. See: Air bag supplemental restraint system Service and Repair
- To access and replace the integrated relay/fusebox in the engine compartment and the connectors, see: Cable, battery to generator, B5254T7 Service and Repair
- For information about the repair of SRS wiring, see: Wiring harness supplemental restraint system (SRS) Wiring Harness Supplemental Restraint System (SRS)
- Checking wiring and terminals Checking Wiring and Terminals

Continue - DONE

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