86
HP Printer
Severity: ModerateWhat Does This Error Mean?
Error 86 on an HP LaserJet printer is a MIO buffer overflow error. The MIO card (the network or interface card in the printer's expansion slot) has received more data than it can handle. The printer's buffer has filled up and it is unable to continue processing the print job.
Affected Models
- HP LaserJet 4000 Series
- HP LaserJet 4050 Series
- HP LaserJet 5000 Series
- HP LaserJet 8000 Series
- HP LaserJet 9000 Series
Common Causes
- A very large or complex print job overwhelmed the MIO card's data buffer
- The MIO card is faulty and cannot properly manage data flow
- The printer's RAM is insufficient for the size of the job being sent
- A network communication problem caused corrupted or repeated data to flood the buffer
- Outdated printer firmware is handling buffer management incorrectly
How to Fix It
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Turn the printer off using the power button. Wait 30 seconds, then turn it back on. This clears the overflowed buffer.
Simply restarting the printer usually clears a one-off buffer overflow caused by a large job.
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On your computer, clear the print queue before restarting the printer. Cancel all pending print jobs to prevent the same large job from being resent immediately.
Go to Settings > Devices > Printers in Windows, click your printer, and select Open print queue to cancel jobs.
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Try breaking large documents into smaller sections before printing. Send 10 pages at a time instead of a 100-page document in one go.
This reduces the amount of data sent at once, which helps if the buffer overflow is caused by document size.
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Check if your printer has expandable RAM and add more memory if possible. More RAM means a larger buffer and fewer overflow errors.
HP LaserJet printers from this era typically support 32MB to 512MB of RAM via DIMM slots inside the printer. Check your model's specifications.
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Update the printer firmware from HP's support website. Firmware updates often include improvements to buffer and memory management.
Go to support.hp.com, search for your printer model, and look for firmware downloads in the drivers section.
When to Call a Professional
If error 86 happens consistently with normal-sized print jobs after upgrading RAM and firmware, the MIO card may need replacement. MIO cards for older HP LaserJet printers are available used for $20 to $60. A technician can confirm whether the MIO card or the formatter board is the root cause.
Frequently Asked Questions
What does buffer overflow mean in plain English?
Think of the buffer like an inbox tray on a desk. When too many papers arrive faster than the worker can process them, the tray overflows and papers fall on the floor. The printer's buffer works the same way — too much data arrives too fast, and the printer cannot handle it all at once.
Will adding more RAM to the printer definitely fix error 86?
It helps, but it is not guaranteed. More RAM increases the buffer size, which reduces the chance of overflow. However, if the MIO card itself is faulty, more RAM will not fix the underlying hardware problem. Start with the free fixes (clearing the queue, splitting the job) before buying RAM.
Does error 86 damage the printer?
No — a buffer overflow is a software-level event, not a hardware failure. The printer detects that its buffer is full and stops safely rather than crashing. No data is permanently damaged, and the printer is fine to use once the buffer is cleared.