What this code means
B0020 can indicate an open circuit or increased resistance in the left side airbag inflator.
An open circuit is a break in an electrical path. Increased resistance means the path has more resistance than the procedure allows. For B0020, the path under investigation belongs to the driver's side airbag inflator. The diagnosis therefore needs to separate a problem associated with that component from a problem elsewhere in its circuit.
The driver's side airbag inflator, its connecting paths and the SRS unit are different possible fault areas. Naming the driver's side airbag inflator in the code does not make those possibilities interchangeable. The steps below narrow the fault area by changing a defined test condition and then checking the individual paths.
What the vehicle may do
- The SRS unit can store this code for high detection-line voltage.
Possible fault areas
- The driver's side airbag may have a problem.
- The LFSA+ or LFSA- circuit may have a problem.
- The SRS unit may have a problem.
The procedure moves through confirmation, an indirect component check and electrical-path checks. In the indirect check, the specified jumper connection is used exactly as described. The result determines whether the component or other related parts remain involved. The later measurements examine LFSA+ and LFSA- through the wiring between the side airbag connector and SRS unit.
Read the result criteria alongside the action that produces them. During the component check, a normal circuit-test result can point to a problem with the named component. During a wire check, an abnormal reading instead points to the checked path. These conclusions belong to different stages of the diagnosis.
Diagnostic path
Understand the stored condition
B0020 means Open or Increased Resistance in the Left Side Airbag Inflator. The SRS unit stores this code when the voltage on its internal detection line is higher than a specified value.
SRS safety before starting
Follow the SRS safety precautions and procedures. You also need to understand the 12 volt battery terminal disconnection and reconnection procedures before you proceed.
Check collision history first
Before you start these checks, find out whether the vehicle was in a collision. If it was, make sure all required components were replaced with new components. Check that those components have the correct part numbers and were properly installed.
Initial confirmation
Turn the vehicle to the ON mode. Wait for 10 seconds. This is the confirmation check for the airbag test that follows.
Check the driver's side airbag circuit
This check evaluates the component through its related components. Before you disconnect the SRS related connector, follow the 12 volt battery terminal disconnection procedure. Wait for at least 3 minutes. Disconnect the driver's side airbag inflator connector (2P). Install a jumper wire between terminals No. 1 and No. 2 of that connector. Turn the vehicle to the ON mode. Wait for 10 seconds. For a normal result, DTC B0020-13 should not be indicated.
If the result is normal, there is a problem with the driver's side airbag. If the result is abnormal, there is a problem with other related components.
For the component test, a normal result means the stated DTC B0020-13 is not indicated after the specified test connection and confirmation. The procedure associates that normal test result with a problem in the driver's side airbag inflator. An abnormal result follows the branch for other related components.
Here, the word normal refers to the response of the circuit test. It does not describe a direct resistance measurement of the driver's side airbag inflator. The wire checks that follow use their own resistance criteria and therefore answer a different question. This distinction is the key to reading the component and circuit branches correctly.
Prepare for the wiring checks
Check wires LFSA+ and LFSA- for an open next. Before you disconnect the SRS related connector, follow the 12 volt battery terminal disconnection procedure. Wait for at least 3 minutes. Disconnect SRS unit connector B (57P). Then disconnect the driver's side airbag inflator connector (2P). Check each wire using the terminal pairs and normal readings that follow.
Check the LFSA+ wire
Keep IG Mode OFF for this check.
- First probe: SRS unit connector B (57P) terminal 4.
- Other probe: driver's side airbag inflator connector (2P) terminal 2.
- Normal reading: less than 1 ohm.
If the reading is abnormal, there is a problem in the circuit.
LFSA+ and LFSA- are identified by different terminal pairs. LFSA+ pairs SRS unit connector B terminal 4 with airbag connector terminal 2. LFSA- pairs SRS terminal 3 with airbag terminal 1. The terminal number at one connector does not carry over unchanged to the other connector.
This wiring stage differs from the earlier jumper check at the airbag connector. The jumper check supplies a DTC-indication result. The two wire checks supply resistance readings between the SRS unit and airbag connector, with IG Mode OFF and the connectors prepared as stated. Less than 1 ohm is the normal criterion for those individual paths, and an abnormal result points to the checked circuit.
Check the LFSA- wire
Keep IG Mode OFF for this check too.
- First probe: SRS unit connector B (57P) terminal 3.
- Other probe: driver's side airbag inflator connector (2P) terminal 1.
- Normal reading: less than 1 ohm.
If the reading is abnormal, there is a problem in the circuit.
When the other checks are normal
If all the other check results are normal, that leaves the SRS unit as the cause. In that case, there is a problem with the SRS unit.
Final check
The airbag circuit check and wire readings can help identify whether the problem involves the airbag, its circuit, or the SRS unit.
Taken together, the results form a chain. The indirect component check establishes which branch to follow; the individual electrical checks identify an abnormal path; and the final SRS-unit conclusion depends on the earlier inspection items being normal. Keep the actual result beside the component or wire that was being checked. That makes the final decision traceable to the procedure, rather than to the wording of the stored code alone.
