B1377 code definition
The B1377 trouble code notes a malfunction with the oil change lamp circuit.
What the B1377 code means
The B1377 code is a standard OBD-II trouble code that detects a circuit issue with the oil change lamp. The oil change lamp is a warning light on the vehicle’s instrument panel that illuminates when the car should have the oil changed. This lamp is normally triggered when the vehicle has driven a certain number of miles. When the powertrain control module (PCM), body control module, or one of the many other control modules (such as the instrument panel control module) notes a circuit failure from the oil change lamp, then the B1377 trouble code will likely be triggered.
What causes the B1377 code?
A few different things can cause the B1377 trouble code to be stored:
- Defective oil change lamp bulb
- Faulty oil change lamp circuit
- Damaged wires, connectors, and fuses in the controller area network (CAN) bus harness
- In rare cases, a malfunctioning PCM, body control module, or CAN bus
What are the symptoms of the B1377 code?
When the B1377 trouble code is present, the oil change Warning Light will likely have issues. The lamp may illuminate even when the vehicle is not due for an oil change, or the lamp may not illuminate at all, even when it should. It is also possible that the lamp will blink repeatedly. In addition to oil change Warning Light failure, the check engine soon Warning Light may illuminate.
How does a mechanic diagnose the B1377 code?
The B1377 code will be diagnosed using an OBD-II trouble code scanner. A reputable technician can use the scanner to observe the freeze frame data for the B1377 code, and also to check for the presence of additional trouble codes. If there are multiple trouble codes detected, then they should be diagnosed in the order that they appear in. The mechanic will then reset the trouble codes, restart the vehicle, and check to see if the B1377 code remains present. If not, then an intermittent error, or an erroneous trigger are likely to blame.
If the code is still detected, then the technician will begin by visually inspecting the electrical components in the CAN bus harness. Any blown fuses, corroded connectors, and damaged wires will need to be replaced. If any of the electrical components appear to be damaged as the result of other issues (such as leaks), then a further inspection for the root of the problem will be required.
Next, the oil change lamp bulb and circuit will be inspected. If the issue remains, then a specialized CAN scanner can be hooked up to help pinpoint the problem.
After any replacements or repairs are made, the technician will need to reset the trouble codes, restart the vehicle, and again check for the presence of the B1377 code. By doing this, the mechanic will know as soon as the problem has been fixed.
Common mistakes when diagnosing the B1377 code
The most frequently made error when diagnosing this code comes from failing to properly follow the OBD-II diagnosis protocol. It is imperative that technicians abide by the protocol step by step, to help ensure efficient diagnoses, and avoid erroneous repairs.
It is common for functioning oil change lamp circuits to be condemned when a fuse or a wire was the only problem.
How serious is the B1377 code?
The B1377 trouble code won’t keep a car from being drivable, but it will likely prevent the oil change reminder system from operating properly. As with all trouble codes, when the B1377 code is detected, an inspection should be scheduled.
What repairs can fix the B1377 code?
Repairs for the B1377 trouble code include:
- Oil change lamp bulb replacement
- Oil change lamp circuit replacement
- Replacement of the electrical components in the CAN bus harness
- In rare cases, replacement of the PCM, CAN bus, or body control module
Additional comments for consideration regarding the B1377 code
The B1377 trouble code is a manufacturer specific code. This means that the definition of the code can vary depending on the manufacturer. While the B1377 represents an oil change lamp circuit failure for many vehicles, it represents a different problem for some makes and models. Technicians should always take into consideration the vehicle they are working on when diagnosing the B1377 code.
Control module failure is very rarely associated with the B1377 code, so all other potential causes should be thoroughly checked before controller damage is presumed. If a control module does require replacement, it will also require reprogramming.
Need help with a B1377 code?
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This article originally appeared on YourMechanic.com as B1377 OBD-II Trouble Code: Oil Change Lamp Circuit Failure and was authored by Brady Klopfer.