b1121 harley code

B1121 Harley Code – What it is and How to Fix it

If you own a Harley Davidson motorcycle, and you’re struggling with your blinkers, it’s possible that the fault code B1121 or B1122 is appearing. These codes symbolize an issue in the left and right turn signal outputs. In this article we’ll quickly cover what causes these issues as well as some of the ways to resolve them so your beloved bike can get back on track.

Understanding B1121 Harley Code

Harley Davidson motorcycles equipped with a turn signal system feature two diagnostic trouble codes (DTCs) related to the Turn Signal Module (TSM). B1121 signals an issue with the left turn signal output, whereas code B1122 indicates a fault in the right.

When the fault code appears, it indicates that communication between the TSM and either side of turn signal circuits is disjointed. This can result from an array of problems like wiring issues, worn out light bulbs, corroded connectors or malfunctioning in the TSM itself.

Causes of B1121 Harley Code

Numerous issues can trigger the B1121 Harley code, some of which are among the most widespread culprits:

  1. Faulty turn signal bulbs: Are you plagued by the B1121 code? If so, it may be because of a burned-out or damaged turn signal bulb. Check all your bulbs and make sure they’re working correctly – that should do the trick.
  2. Wiring issues: Electrical malfunctions, such as a short circuit or open circuit in the wiring, can result in the TSM being unable to communicate with turn signal circuits.
  3. Damaged connectors: Corroded or compromised connectors can obstruct the exchange of information between the TSM and signal circuits, creating difficulties.
  4. TSM issues: In the event of a TSM malfunction, it can result in the B1121 Harley code being displayed.

Fixing B1121 Harley Code

If you’re trying to troubleshoot the B1121 Harley code, there are a few solutions available. Consider these:

  1. Check the turn signal bulbs: Guarantee that all your turn signal bulbs are in working order. If you notice any malfunctioning lights, make sure to replace them right away.
  2. Inspect the wiring: Carefully inspect the turn signal circuit for any broken, frayed or disconnected wires. If damaged, be sure to repair them immediately.
  3. Clean connectors: Ensure that any dust and corrosion is removed from the connectors, making sure they are securely fastened.
  4. Check the TSM: If the above strategies fail to produce results, you may need to inspect your TSM. However, diagnosing and mending a malfunctioning TSM can be complicated and necessitate specialized tools.
  5. Install Load Equalizers: If you’re one of the many drivers who have recently traded in their standard turn signals for LED alternatives, you may find that they flash too rapidly. This issue is caused by the lower power draw of LEDs compared to traditional bulbs. Fortunately, this can be resolved with a set of load equalizers to keep your lights working properly and safely.

Preventing B1121 Harley Code

Taking precautionary measures is undoubtedly more beneficial than attempting to mend a problem after it occurs. Make sure your Harley Davidson motorcycle never encounters B1121 or other fault codes with these preventative strategies:

  1. Regular maintenance: By performing routine maintenance on your motorcycle, you can identify and repair potential issues before they become more costly problems.
  2. Check the wiring: Periodically, check the wiring and connectors for any signs of wear or damage. If you spot these indicators, don’t hesitate to have them repaired or replaced immediately.
  3. Replace turn signal bulbs: Swiftly replacing your turn signal bulbs the moment you observe them not functioning appropriately is crucial to avoiding additional harm to the turn signal system.
  4. Use quality parts: When restoring or changing any parts of your motorcycle, always opt for high-end components. Inexpensive and low-grade alternatives can do more harm than good in the future.

To wrap it up, if you’re facing issues with your turn signal system and indicating fault codes B1121 or B1122 on the meter, now you know how to go about tackling them. From checking the bulbs to inspecting wiring and cleaning connectors as well as using load equalizers, these steps can restore full functionality of your motorcycle’s turning light system. If by any chance these methods don’t help fix things for you then professional support is needed-to evaluate and mend a malfunctioning TSM module.


The B1121 Harley code signals a potential issue with the wiring of your left turn signal. Possible sources may include faulty bulbs, connectors or incorrect circuit set-up. If taking steps to correct it yourself doesn’t work, you might want to consult an expert for assistance in repairing your Harley Davidson motorcycle – not only so that it runs smoothly but also looks its best.


Below are some FAQs about the B1121 Harley code:

What does the B1121 Harley code mean?

A B1121 Harley code is a diagnostic fault that relates to the turn signal system of a Harley Davidson bike. Specifically, this code highlights an issue with the left output for the turning signals.

What causes the B1121 Harley code?

Several aspects can bring about the B1121 Harley code; these may include broken turn signal bulbs, wiring problems, malfunctioning connectors, or difficulties with your TSM.

How do I fix the B1121 Harley code?

If your Harley is displaying the B1121 code, you may need to inspect the turn signal bulbs, wiring and connectors for potential solutions. Cleaning these components could help resolve any issues experienced when using load equalizers. However, if none of these methods prove successful, it’s probably best to have a professional diagnose and repair the TSM to ensure optimal performance from your bike.

Can I prevent the B1121 Harley code from appearing?

Stop the B1121 Harley code and other fault codes from appearing with regular maintenance, a thorough inspection of wiring/connectors, quality turn signal bulbs and parts. Practicing preventive care is your best defense against potential problems in the future.

Can LED turn signals cause the B1121 Harley code?

When using LED turn signals, the low power draw can trigger the B1121 Harley code. Fortunately, fitting load equalizers will rectify this issue of excessive blinking.

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