B1993 code definition
When the Powertrain Control Module (PCM) receives a voltage signal from the driver's side, side mount airbag circuit that varies from the manufacturer's specifications, a B1993 trouble code can be stored. Other trouble codes to look for that the PCM could store in addition to the B1993 code include a B1992, B1994, B1995, B1996, B1997, B1998, and B1999 code.
What the B1993 code means
When the PCM detects a variance in the voltage from the driver's side side-mount air bag circuit that falls out of the range recommended by the manufacturer, a B1993 trouble code is stored and the Supplemental Restraint System (SRS) warning light illuminates. In addition to a stored code and warning light illumination, many vehicles disable the SRS system with the storage of this code.
What causes the B1993 code?
When diagnosing a B1993 trouble code, mechanics should keep in mind the most common cause, including loose, faulty, or otherwise damaged wiring, connectors, and components. In addition, a fault with the ground wire or a fault within the airbag components can cause storage of a B1993 trouble code. A loose battery connection, corroded battery cable connectors, or a bad battery can also cause this code storage.
What are the symptoms of the B1993 code?
The primary symptom of a B1993 trouble code is usually just the illumination of the SRS warning light. If the light is not working, the PCM notifies the driver via a series of audible tones that go off while driving.
How does a mechanic diagnose the B1993 code?
To diagnose a B1993 trouble code, the mechanic needs to use an appropriate OBD-II scanner and a digital multimeter with the output set to 10 mA or less. The mechanic must also perform the following steps while diagnosing the code:
Start by clearing the code and then retesting the system to see if that fixes the problem.
If the code returns, the mechanic should download the freeze frame data and any stored trouble codes.
Next, the mechanic should start the vehicle and test the airbag wiring while the vehicle is running. This includes shaking the wiring harness to see if there is any intermittent operation created by a possible faulty or loose wire or connector.
While the vehicle is running, the mechanic should test drive the vehicle to see if he can get the code to repeat during driving conditions.
If the code returns, the mechanic should first disconnect both battery cables before proceeding to more thoroughly inspect the wiring, connectors, or components of the wiring harness.
While the battery is disconnected, the mechanic should check the battery to see if it is bad, inspect the battery cable clamps for damage, and look for any corrosion on the battery cable terminal ends or on the battery posts.
After replacing any faulty or damaged wiring or connectors, the mechanic should also reconnect the battery cables, reprogram the airbag control module if needed, and clear the code.
Retest the system, and if the code returns, check the reference voltage and the ground signal at the driver's side, side mount airbag circuit with the digital multimeter.
If no signal is present, the mechanic should suspect a bad circuit. They should disconnect the PCM and other related control modules and check the continuity of the circuit with the battery ground.
The mechanic can also check the continuity between the relevant control modules and the PCM and the continuity between the PCM and the side mount airbag circuit.
Finally, the mechanic should clear the code, once all repairs and replacements have been made, and retest the system to see if the code returns.
Common mistakes when diagnosing the B1993 code
Mechanics often make the mistake of replacing more expensive parts, such as the side mount airbag, first without checking the wiring or connectors for looseness or damage. The result is the problem remains unfixed and the code returns.
How serious is the B1993 code?
The storage of a B1993 trouble code is very serious. When this code is stored, the vehicle often shuts down the SRS system, which could lead to injury or death in the case of an accident. You should get this code fixed as soon as possible once you are aware of it.
What repairs can fix the B1993 code?
Repairing and clearing a B1993 trouble code could be as simple as replacing a few wires, or it could require the mechanic to replace other components, such as the side mount airbag. To repair a B1993 trouble code, a mechanic needs to take the following steps:
Replace any faulty or damaged wiring, connectors, and components found during the initial inspection.
Replace the battery if it is bad.
Clean or replace the battery cable connectors if damaged or corroded.
Replace the driver's side side-mount airbag circuit if it is at fault.
Replace the driver's side side-mount airbag if it is bad.
Replace the specific airbag control module if it is not working correctly.
Additional comments for consideration regarding the B1993 code
The mechanic needs to make sure that they disconnect both battery cables before proceeding with the inspection of the driver's side side-mount airbag. They should also wait three minutes once they do disconnect the battery cables to ensure that the airbag does not deploy during the inspection.
Need help with a B1993 code?
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This article originally appeared on YourMechanic.com as B1993 OBD-II Trouble Code: Driver Side Side-Mount Air Bag Circuit Short to Ground and was authored by Cheryl Knight.