Fault in Rear Backup Lamp Circuit.
Indicates an issue with the rear backup lamp system.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The rear lights that should turn on when you shift into reverse are not working due to a problem in the circuit or components.
What the computer is actually seeing
The Body Control Module (BCM) monitors the voltage in the rear backup lamp circuit when the vehicle is in reverse. It expects to see battery voltage (around 12 volts) when the lamp relay is activated.
What a healthy reading looks like
Expected voltage at the rear backup lamp circuit should be close to battery voltage (12-14 volts) when the vehicle is shifted into reverse.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Check the fuse for the rear backup lamps; replace if blown. If okay, proceed to step 2.
- 22. Inspect the backup lamp switch for proper operation. Disconnect the connector and check continuity; it should be closed when in reverse. If faulty, replace the switch.
- 33. Check for voltage at the backup lamp circuit with a multimeter when the vehicle is in reverse. You should see around 12-14 volts. If not, check for open wiring in the harness.
- 44. Inspect the rear backup lamps themselves; replace any that are burnt out or faulty. If all tests pass, the issue may be with the Body Control Module.
Common causes
- Blown fuse for the backup lamps
- Faulty backup lamp switch
- Damaged wiring or connectors in the circuit
- Burnt out backup lamps
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Yes, but you should fix the backup lights soon for safety when reversing.
Will this fault code come back after I reset it?
If the cause is fixed, it should not return. If there's still an issue, it will trigger again.
Why do I see this code with B1551?
Both codes pertain to the backup lamp circuit; they often trigger together due to related issues.
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