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Testing Air Bag Circuit 1 (500E)

WARNING: This page is about a different car, the 1993 Mercedes-Benz 500SEL and 1993 Mercedes-Benz 500E. However, it is still accessible from the selected car via links, so may be relevant.
  1. Connect SRS tester to SRS Red 10-pin connector. See SRS TESTER PREPARATION  . See SRS RED CONNECTOR LOCATION  table under DISABLING & ACTIVATING AIR BAG SYSTEM.
  2. Turn ignition switch to ON position. Slowly turn steering wheel completely to left and right several times while reading SRS tester display resistance value. Resistance reading should be 2-20 ohms. If resistance reading is 2-20 ohms, go to next step. If reading is not 2-20 ohms, go to step 4).
  3. Push SRS tester grounding button to test isolation resistance (wiring harness to ground connection). Resistance reading should be 20,000 ohms to infinity. If reading is as specified, go to TESTING AIR BAG CIRCUIT 2 - ETR under SRS COMPONENT TESTING  . If reading is not as specified, replace SRS wiring harness. Perform system operation check to ensure system is functioning properly. See SYSTEM OPERATION CHECK  . If SRS is now functioning properly, test sequence is completed.
  4. Disconnect battery. Locate and unplug slip ring 2-wire SRS Orange or Yellow connector behind left side of instrument panel, near steering column. See Figure . For positive identification, slip ring 2-wire SRS Orange or Yellow connector uses a Purple wire and a Green wire.
  5. With slip ring connector unplugged, resistance should be infinity. If resistance is infinity, go to next step. If resistance is less than infinity, SRS wiring harness is shorted to ground. Replace SRS wiring harness. Ensure system is functioning properly. See SYSTEM OPERATION CHECK  .
  6. If reading is infinity, connect jumper wire across slip ring 2-wire SRS harness-side connector terminals. DO NOT  connect jumper wire across the connector leading to slip ring-air bag module. Resistance reading should be 0-1 ohm. If reading is 0-1 ohm, go to next step. If reading is not 0-1 ohm, replace SRS wiring harness. Perform system operation check to ensure system is functioning properly. See SYSTEM OPERATION CHECK  .
  7. Ensure battery is disconnected. With slip ring 2-wire connector still unplugged, remove air bag module from steering wheel and disconnect air bag module connector. See DRIVER-SIDE AIR BAG MODULE  under REMOVAL & INSTALLATION.
  8. At steering wheel, connect jumper wire across slip ring-to-air bag module connector terminals. Reconnect 2-wire SRS Orange or Yellow slip ring connector behind instrument panel, near steering column. Now note SRS tester resistance reading. Resistance should be 0-25 ohms.
  9. If resistance is 0-25 ohms, replace air bag module. Ensure system is functioning properly. See SYSTEM OPERATION CHECK  . If resistance is not 0-25 ohms, remove steering wheel. See STEERING WHEEL  under REMOVAL & INSTALLATION.
  10. Prepare to connect jumper wire across slip ring carbon contacts. First, lightly touch/connect one end of jumper wire to carbon contact closest to steering shaft. Second, touch/connect other end of same jumper wire to adjacent contact nearest outer edge of column. Next, connect a second jumper wire to remaining set of contacts. See Figure .
  11. Note SRS tester resistance reading. Resistance should be 0-1 ohm. If resistance is 0-1 ohm, replace slip ring assembly on bottom of steering wheel. See SLIP RING ASSEMBLY  under REMOVAL & INSTALLATION. Perform system operation check to ensure system is functioning properly. See SYSTEM OPERATION CHECK  .
  12. If resistance is not 0-1 ohm, replace carbon contacts assembly in steering column. See SLIP RING ASSEMBLY  under REMOVAL & INSTALLATION. Perform system operation check to ensure system is functioning properly. See SYSTEM OPERATION CHECK  .
CAUTION: Contact surfaces between slip ring and carbon contacts must be clean. DO NOT  touch carbon contact surfaces with fingers, as static electricity may activate air bag when reassembled.
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