System B 04
Overview of possible fault
- Warning light, airbag
- Supply voltage
- Firing circuit, driver
- Firing circuit, passenger
- Buckle, driver
- Buckle, passenger
- Child seat detection
- Control unit faulty
NOTE: A plus sign (+) present in the line or not present indicates a loose contact. A counter is started when the symbol changes from not present to present. This counter indicates how often the change took place from present to not present.
When a fault is identified, a fault start clock is started. The fault start clock shows the time in hours, minutes and seconds that has passed since the fault first occurred.
When a changeover occurs from present to not present, a fault stop clock is started. The fault stop clock shows the time which has passed since the fault was no longer present. However, with both clocks, only ignition on times are shown. This means that the clocks are stopped when the ignition is switched off.
Fault Overview:
Test point 1
Firing circuit, driver
Fault codes 04, 05, 20, 21, 36
Fig. 1:
1. Remove driver's airbag unit.
2. Attach the special tool 9516 instead of the airbag unit.
Fig.2:
3. Clear the fault memory
4. Check whether the fault appears again.
a) If the fault does not appear again, replace the airbag unit.
b) If the fault appears again, disconnect plug connection to the contact unit and attach special tool 9516/1.
5. Clear the fault memory
6. Check whether the fault appears again.
a) If the fault does not appear again, replace the contact unit.
b) If the fault appears again, check the wiring harness for pinches and chafing damage.
c) If no fault is found on the wiring harness, replace the triggering unit.
NOTE: Signal not plausible.
This fault path is checked only during the triggering unit self-test, i.e. updating of the fault during the cyclical tests does not take place.
If the fault memory is erased, the ignition must be switched off, the ignition key removed and the ignition switched on again in order to check the fault path. Only in this way is another self-test carried out.
Test point 2
Firing circuit, passenger
Fig. 3:
Fault codes 10, 11, 26, 27, 39
1. Disconnect the plug connection to the passenger's airbag unit.
2. Attach the special tool 9516 in conjunction with special tool 9566.
3. Clear the fault memory.
4. Check whether the fault appears again.
a) If the fault does not appear again, replace the passengers airbag unit
b) If the fault appears again, check the wiring harness for pinches and chafing damage.
c) If no fault is found on the wiring harness, replace the triggering unit.
NOTE: Signal not plausible.
This fault path is checked only during the self-test of the triggering unit, i.e. updating of the fault during the cyclical tests does not take place.
If the fault memory is cleared, the ignition must be switched off, the ignition key removed and the ignition switched on again in order to check the fault path. Only in this way is another self-test carried out.
Test point 3
Supply voltage
Fault code 03
1. Inspect the battery and generator.
2. Inspect the plug connection on the triggering unit for corrosion.
Test point 4
Warning light, airbag
Fault codes 01, 02
1. Inspect the fuse for the supply voltage (terminal 15) for the instrument cluster.
2. Inspect the bulb and replace it if necessary.
3. Inspect the line from the triggering unit pin 7 to the warning light for continuity and short circuit to positive or negative.
Test point 5
Buckle, driver
Fault codes 44, 45, 46, 50
NOTE: Only on USA vehicles:
1. Disconnect the plug connection X16.
2. Connect ohmmeter on the pin side on pins B7 and B8.
Display: approx. 400 ohm
NOTE: The belt tongue must not be inserted in the buckle.
3. Connect ohmmeter on the pin side on pin B7 and ground.
Display: Infinity ohm
4. Connect ohmmeter on the pin side on pins B7 and B8. Insert the belt tongue in the buckle.
Display: approx. 100 ohm
5. Inspect the wiring harness to the triggering unit for pinches and chafing damage.
Test point 6
Buckle, passenger
Fault codes 47, 48, 49, 51
NOTE: Only on USA vehicles:
1. Disconnect the plug connection X17.
2. Connect ohmmeter on the pin side on pins B7 and B8.
Display: approx. 400 ohm
NOTE: The belt tongue must not be inserted in the buckle.
3. Connect ohmmeter on the pin side on pin B7 and ground.
Display: Infinity ohm
4. Connect ohmmeter on the pin side on pins B7 and B8. Insert the belt tongue in the buckle.
Display: approx. 100 ohm
5. Inspect the wiring harness to the triggering unit for pinches and chafing damage.
Test point 7
Child seat detection
Fault codes 70, 71, 72, 73
1. Disconnect the plug on the triggering unit
2. Connect ohmmeter to plug I pin 23 and ground. Plug of child seat not inserted.
Display: approx. 2 kohm
Plug of child seat inserted.
Display: approx. 260 ohm
3. Inspect the wiring harness to the triggering unit for pinches and chafing damage.
Test point 8
Control unit
Fault code >= 100
Replace the triggering unit.
Test point 9
Unknown fault code
Fault code XXX
1. Inspect the ground points for corrosion.
2. Inspect the ignition on the secondary side.
3. Clear the fault memory.