What this code means
B0079 can indicate an open or increased resistance in the driver's seat belt outer lap tensioner.
An open circuit is a break in an electrical path. Increased resistance means the path has more resistance than the procedure allows. For B0079, the path under investigation belongs to the driver's seat belt outer lap tensioner. The diagnosis therefore needs to separate a problem associated with that component from a problem elsewhere in its circuit.
The driver's seat belt outer lap tensioner, its connecting paths and the SRS unit are different possible fault areas. Naming the driver's seat belt outer lap tensioner 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 may store this code for high detection-line voltage.
Possible fault areas
- The lap tensioner may have a fault.
- The related wiring may have an open or increased resistance.
- The SRS unit may have a fault.
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 LLP+ and LLP- through the wiring between the lap tensioner 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
B0079 points to an open or increased resistance in the Driver's Seat Belt Outer Lap Tensioner. We will call it the lap tensioner. The SRS unit stores this code when voltage on its internal detection line is higher than a specified value.
SRS safety preparation
Follow the SRS safety precautions and procedures. Use the specified 12 volt battery terminal disconnection and reconnection procedure.
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 of the correct part number. Also make sure those components were properly installed.
Initial confirmation
Turn the vehicle to the ON mode. Wait for 10 seconds. You will use this confirmation procedure in the next check.
Check the lap tensioner circuit
This check evaluates the component through its related components. This check tests the 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 seat belt outer lap tensioner connector (2P). Install a jumper wire between terminals No. 1 and No. 2 of that connector. Use the confirmation procedure: turn the vehicle to the ON mode, then wait for 10 seconds.
For a normal result, DTC B0079-13 should not be indicated. If the code is not indicated, this circuit check points to a problem with the lap tensioner. If the code is still indicated, it points to other related components.
For the component test, a normal result means the stated DTC B0079-13 is not indicated after the specified test connection and confirmation. The procedure associates that normal test result with a problem in the driver's seat belt outer lap tensioner. 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 seat belt outer lap tensioner. 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
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). Also disconnect the driver's seat belt outer lap tensioner connector (2P).
Check LLP+ resistance
Keep IG Mode OFF for this LLP+ open wire resistance check.
- First probe: SRS unit connector B (57P) female terminal 17.
- Other probe: driver's seat belt outer lap tensioner connector (2P) female terminal 2.
The reading should be less than 1 ohm. That is the normal result. If the result is abnormal, there is a problem in the circuit.
LLP+ pairs SRS unit connector B terminal 17 with lap-tensioner connector terminal 2. LLP- pairs SRS terminal 18 with tensioner terminal 1. These are separate paths, even though their resistance criteria are the same.
The jumper check at the tensioner connector produces the code-indication result used for the component branch. The later measurements examine resistance between the specified disconnected connectors. Less than 1 ohm is the normal reading for each listed wire path. An abnormal reading points to the circuit being measured, while the remaining SRS-unit conclusion depends on the other inspection items being normal.
Check LLP- resistance
Keep IG Mode OFF for this LLP- open wire check too.
- First probe: SRS unit connector B (57P) female terminal 18.
- Other probe: driver's seat belt outer lap tensioner connector (2P) female terminal 1.
The reading should be less than 1 ohm. That is the normal result. If the result is abnormal, there is a problem in the circuit.
When the checks point to the SRS unit
If all the other checks are normal, the remaining cause is the SRS unit. In that case, the result identifies a problem with the SRS unit.
Final check
The circuit checks can narrow the fault to the lap tensioner, related wiring, or 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.
