HP Color LaserJet 5500 – 51.2 Error on the Display

The 51.2 error is a laser error. It means the laser motor didn’t get up to operating speed in time.

The service manual says the 2 in the error code will be followed by an additional number, but the machine I just serviced was reporting a 51.2Y Error (a letter, not a number) indicating a problem with the yellow laser scan assembly. When I switched the yellow laser scanner assembly (laser unit) to the cyan slot the 51.2Y error turned to a 51.2C error.

In monochrome printers the laser scanner motor doesn’t typically turn on so the machine usually goes to a ready state until you use it; then you get the 51 error. With color laser printers, after the machine initializes it does a calibration, which uses the laser scanner assemblies. So, on color machines you most likely will get the error on start up while performing the calibration.

Most of the time the 51.2 errors are a result of the laser scanner motor locking up due to dirty or dry bushings and motor shaft. If the motor hasn’t totally locked up you will hear a loud, sometimes high pitched noise when it goes to calibrating and as the motor starts to speed up.

The best thing to do is to follow the removal procedure in the Service Manual (page 311).

Take the top cover off the specified laser scanner assembly and test the motor. It should rotate freely. If it doesn’t, remove the clear plastic piece holding the motor together, pull the polygon mirrors on top off, use alcohol to clean the shaft and motor bushing out, apply a small amount of light weight oil to the shaft and bushings, and reinstall the motor.

To test the assembly, put it back in the machine but switch it with another of the laser scanner assemblies. All four laser units are the same so switching them is not an issue and for testing purposes it works out great.  Once you have it in, put the machine back together and test again.  If the error message switches to the slot you put the suspect laser unit into, then you know you have a laser unit error and not something else.  Now’s the time to order a replacement laser scanner assembly [part #RG5-6736]

WARNING: The removal procedure takes about 30 to 45 minutes, if you know what you’re doing, and requires that you remove lots of parts. Most likely this error will require replacement of the laser scanner assembly. So I leave it up to you how far you want to go with this before you order the parts. In this post, I just wanted to share some troubleshooting tips if you’re unsure and want to verify if the laser scanner is truly the issue.

On older machines where laser scanners are becoming hard to find or are really expensive I will let the lubrication trick go. On machines where the parts are relatively cheap and I can still get them I tell the customer I temporarily got the machine working but would recommend replacing the laser scanner assembly to avoid unwanted call backs.

Note:  The mirrors on the polygon motor are extremely sensitive. When handling the mirrors try not to touch them and when you get the parts back together make sure you use a Q-tip or soft cloth and gently wipe down the mirrors. Scratches, dirt, or oil marks on the mirrors will effect print quality and require taking the machine back apart for more cleaning or replacement.

BTW, I’m not showing the laser scanner removal procedure in this post because it’s a somewhat involved procedure. But you can access the instructions in the service manual, which is on Market Point’s website here.

Kevin Gumpp is a certified printer technician and freelance writer for Market Point. Market Point is a HP PartsOne Partner selling HP printer parts. If you have a question for Kevin regarding this topic or have any other printer repair related questions or topics you would like more information on, please send an email to maryp@marketpoint.com.

One thought on “HP Color LaserJet 5500 – 51.2 Error on the Display

  1. Polishing the mirror with a CLEAN, DRY, Q-Tip is good. I have found no solvent, including 85% pure Ethanol, that will not leave a haze on the mirror.


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