HP OfficeJet Pro 6978 Blank White Screen After CMOS Battery Replacement: Causes, Reset Options, and Troubleshooting

Question

I have an HP OfficeJet Pro 6978 that I originally disassembled while trying to replace the CR2032 CMOS battery, hoping that replacing the battery might correct a printing problem. After replacing the battery and reassembling the printer, the control panel lights up with a white background, but nothing appears on the screen-no menu, icons, or other controls.

I have taken the printer apart several times. I first reinstalled the original battery, then tried another new CR2032 battery. Each time, I carefully checked the ribbon cables and other connections before reassembling the printer, but the control panel still shows only a blank white screen.

Is there a reset button on the back of the control panel, motherboard, or somewhere else that needs to be pressed after replacing the CMOS battery?

The printer is still partially functional. I can scan from the computer using HP software, but if I attempt to print a report through the HP 6978 software, I receive a "device is busy" message. It seems as though the printer or its control-panel menu is getting stuck during startup. What could cause this, and what should I check?

This question relates to the HP OfficeJet Pro 6958, 6968, and 6978 printer family and the type of repair discussed in our Printhead Stuck on the Right / Carriage Jam video [https://www.youtube.com/watch?v=rNGF5ZTuJN4].

Answer

The CR2032 Battery Probably Does Not Require a Special Reset

The first thing I would point out is that I would not expect replacing the CR2032 battery itself to require pressing a hidden reset button on the control panel. I am not aware of a user-accessible physical reset switch on the HP OfficeJet Pro 6978 that must be activated simply because the coin-cell battery was changed.

That battery is not comparable to a replaceable ink cartridge or maintenance component that must be electronically acknowledged after installation. Therefore, if the printer worked differently immediately after disassembly, I would concentrate much more heavily on something that happened during the disassembly/reassembly process than on the battery needing to be "registered."

I also would not continue repeatedly changing between the old and new CR2032 batteries. Since changing the battery multiple times has produced exactly the same white-screen symptom, the battery is becoming a less likely explanation.

A White Screen Is Different From a Completely Dead Screen

The fact that the LCD becomes bright white is actually an important diagnostic clue.

A completely dark control panel might suggest that the panel is receiving no power at all. A white illuminated display, however, indicates that at least part of the display assembly is receiving power because the LCD backlight is operating.

What may be missing is the data or initialization required to actually draw the HP menu and graphics onto the LCD.

That can happen because of several possibilities:

• The display ribbon cable is not fully seated.

• The cable is inserted at a slight angle.

• The cable is inserted in the wrong orientation.

• One or more conductive contacts on the ribbon cable are damaged.

• A ZIF connector locking tab is loose or broken.

• The ribbon cable has developed a microscopic tear or crease.

• The connector on the control panel has been damaged.

• The corresponding connector on the printer's main board has been damaged.

• The panel is receiving its backlight voltage but not its data/control signals.

• The control panel electronics themselves have failed.

• The main board is failing to complete the printer's normal startup sequence.

This is why simply looking at a ribbon cable and confirming that it appears to be connected does not always eliminate it as the cause.

Check the Ribbon Cable and ZIF Connector Very Carefully

Because this problem began immediately after the printer was taken apart, I would put the control-panel ribbon connection near the top of the diagnostic list.

Disconnect power from the printer before manipulating these cables.

When inspecting a flat flexible cable, pay attention to how deeply and evenly it enters the connector. The two sides should normally enter the connector to approximately the same depth. A cable can look connected while being slightly crooked, leaving several contacts disconnected.

Also examine the exposed metal contacts closely. Look for:

• Scratches

• Fold marks

• Creases

• Darkened contacts

• Contamination

• Missing conductive material

• Torn cable edges

Pay particular attention to the ZIF connector's locking mechanism. These small plastic locking bars are easy to damage during repeated disassembly. If the lock no longer clamps the ribbon firmly, the cable might look correct while making unreliable electrical contact.

Do not force the cable farther into the connector. These connectors and cables are delicate.

Check Every Cable That Was Disturbed, Not Only the LCD Cable

Another possibility is that the display itself is connected correctly but another subsystem is preventing the printer from completing initialization.

On modern multifunction printers, startup involves communication among several assemblies. If a cable associated with the scanner, carriage system, sensors, control panel, or another internal assembly was disconnected during the repair and is now incorrectly seated, the firmware can become stuck waiting for that subsystem.

That would also fit reasonably well with your second symptom:

"Device is busy."

The computer can apparently still communicate with the printer well enough to recognize it and operate at least some scanner functions, but printing does not reach a ready state.

That suggests that the entire main board is not completely dead. At least some processor, communication, and scanner functionality remains operational. However, the printer may not be completing the initialization necessary to enter its normal printing-ready state.

Scanning Still Working Is an Important Clue

Your ability to scan from the computer is particularly interesting.

It means we should probably not treat this as a simple "printer has no power" condition. The printer is alive enough for the computer to communicate with it and invoke scanner functionality.

Instead, we may be dealing with a partially operating machine in which one part of the startup sequence has failed.

The combination of:

white illuminated control panel + scanning works + printing reports "device is busy"

makes me more suspicious of an initialization, communication, display, cable, or main-board problem than of the CR2032 battery itself.

Perform a Full Power Reset Before Disassembling It Again

Before taking the printer apart for a fourth or fifth time, I would try a complete power reset.

With the printer powered on if possible, disconnect the power cord from the printer. Disconnect the cord from the electrical source as well, wait at least 60 seconds, and then reconnect the printer directly to a wall outlet rather than through a surge protector or power strip.

HP recommends this type of power reset as one of its standard troubleshooting procedures for blank control-panel displays. (HP Support)

This procedure is different from changing the CR2032 battery. You are trying to completely remove operating power from the electronics and allow the machine to restart from a fresh power-on state.

I would not expect this alone to repair a damaged cable or connector, but it is worth eliminating a temporary startup-state problem before doing more invasive work.

Firmware Is Another Possibility, but I Would Check Hardware First

HP has also historically recommended checking printer firmware when an OfficeJet Pro 6978 develops white-screen behavior. (community.hp.com)

However, in your particular case, the timing is important.

You said the screen became white after the printer was physically disassembled.

That strongly changes the diagnostic priorities. If a working display becomes abnormal immediately following disassembly, I would first suspect something that was moved, disconnected, pinched, reversed, or damaged before assuming that firmware happened to fail at exactly the same time.

If the printer remains reachable over USB or the network and HP's software can identify its firmware version, checking for an applicable firmware update may still be worthwhile. HP currently provides firmware and troubleshooting resources on the HP OfficeJet Pro 6978 support page [https://support.hp.com/us-en/product/troubleshooting/hp-officejet-pro-6978-all-in-one-printer-series/model/11161264]. (HP Support)

I would not interrupt a firmware update, disconnect power during one, or attempt unofficial firmware procedures without understanding the risk, because a failed firmware-writing operation can create a much more serious main-board problem.

Examine the Control Panel Cable for Damage Caused During Reassembly

Ribbon cables can also be damaged when the printer housing is put back together.

For example, the cable might become:

• Pinched between two plastic panels

• Pulled too tightly

• Folded at an unusually sharp angle

• Trapped beneath a screw boss

• Partially pulled out while another component is installed

A ribbon cable can still look normal afterward while having one or more internally fractured conductors.

If you have already reseated the connector several times with no change, inspection or substitution of the cable becomes more important.

Be Especially Careful With Connector Orientation

Before reconnecting any ribbon cable, compare its orientation with photographs taken before disassembly, the original cable routing, or reliable reference material.

Flat cables do not universally install with the exposed contacts facing the same direction. Depending on the connector, the conductive side may face up or down.

Installing a cable backward can result in no communication even though the cable appears perfectly seated.

More seriously, depending on the circuit design, connecting certain cables incorrectly can potentially place power on a signal line. Therefore, I would not repeatedly reverse cables experimentally.

Inspect the Main Board Around the CMOS Battery

Since the repair originally involved the coin-cell battery area, I would also inspect that region of the board carefully.

Look for anything that might have happened while removing or installing the battery:

• Scratched traces

• Bent battery-holder contacts

• Damaged nearby surface-mount components

• A screwdriver slipping onto the board

• Conductive debris

• A displaced connector

• A cracked solder joint

• A component accidentally knocked off the board

These parts can be very small. Good lighting and magnification can make a major difference.

Also make sure the battery is actually the correct 3 V CR2032 type and that its polarity matches the battery holder markings.

Again, though, because you have already reproduced the same problem with both the original battery and more than one replacement, I would not make the battery itself the leading suspect.

The Original Printing Problem and the New White-Screen Problem May Be Separate

There is another important diagnostic distinction here.

You originally opened the printer because it would not print, and you hoped the CMOS battery might correct that problem.

Then, after disassembly, the blank-white-screen problem appeared.

Those may be two separate failures.

The first failure could involve the carriage system, printhead, PFG mechanism, paper-feed mechanism, sensors, firmware state, or another printing subsystem. The second failure could have been introduced during disassembly through a cable or connector problem.

That distinction matters because repairing the white display may return you to the printer's original fault rather than automatically solving everything.

"Device Is Busy" Is a Symptom, Not Necessarily the Root Cause

I would not treat the "device is busy" message as a specific hardware error code.

It usually means the computer can see the printer, but the printer is not currently accepting the requested operation.

In this situation, possible reasons include:

• The printer has not completed startup.

• An internal hardware fault is preventing the machine from reaching Ready status.

• The control system is waiting for user input that cannot be displayed.

• A carriage or mechanical subsystem cannot initialize.

• The firmware is hung.

• The printer is processing or believes it is processing another operation.

• Communication between internal boards or assemblies has failed.

Because the LCD is unavailable, there could theoretically be an error or confirmation message that would normally appear on the control panel but is currently invisible to you.

There Is No Specific Numeric Error Code in This Case

No numeric HP error code was included in the question. The messages and symptoms being diagnosed here are:

• Blank white control-panel display

• "Device is busy"

• Printer unable to complete normal printing

• Scanner still accessible through computer software

The original video topic concerns a printhead/carriage stuck on the right side or carriage jam/PFG-related problem, but that should be diagnosed separately from the newly introduced blank-screen condition unless you find evidence connecting the two.

A Practical Diagnostic Order

If this were on my bench, I would approach it approximately in this order:

1. Perform a full AC power reset.

2. Verify that the correct CR2032 battery is installed with correct polarity.

3. Disconnect power and carefully inspect the LCD/control-panel ribbon cable.

4. Inspect both ZIF connectors and their locking tabs.

5. Confirm the cable orientation from a reliable reference.

6. Check the ribbon for creases, tears, scratches, or pinching.

7. Reseat every connector that was disturbed during the original disassembly.

8. Inspect the battery area and surrounding main-board components under magnification.

9. Check whether the printer is accessible through its network interface, USB software, or Embedded Web Server.

10. Check the installed firmware and applicable HP firmware options if hardware connections appear correct.

11. If possible, test with a known-good control panel or known-good display cable.

12. If a known-good panel and cable still produce a white screen, suspicion moves increasingly toward the main board or its display/interface circuitry.

Substituting known-good parts is especially valuable once visual inspection stops producing useful information. Without board-level measurements or known-good components, it becomes difficult to distinguish confidently between a damaged LCD assembly and a main-board signal problem.

If the White Screen Started Immediately After Reassembly, Recheck What Changed

The strongest diagnostic clue is still the timing.

Before opening the printer, you apparently had a printing problem.

After opening and reassembling it, you had a new control-panel problem.

Whenever a new symptom appears immediately after a repair attempt, the most productive approach is usually to trace everything that was physically changed during that repair.

That does not necessarily mean something was installed incorrectly. Sometimes an old cable, brittle connector, or marginal solder joint simply fails after being disturbed. But the repair area is still the logical place to begin.

Addressing printer issues can be a complicated affair because so many problems require hands-on inspection, measurements, part substitution, and mechanical testing. For that reason, we're not able to provide individual remote troubleshooting, repair suggestions, or ongoing technical support for printer repairs. We do offer an in-person evaluation and repair service through our BCH Technologies printer diagnostic and repair facility [https://bchtechnologies.com/printer-repair-service]. Because demand is high, repairs are handled on a first-come, first-served basis, and it may take a few weeks before an appointment or drop-off can be accommodated. Our service can address either complete printers or certain individual parts, and the service page provides instructions on how to proceed. We also recognize that professional repair is not always the most economical option, so we strongly encourage self-help and independent research when appropriate. You can search YouTube or visit the BCH Technologies YouTube channel [https://youtube.com/@bchtechnologies] and use the search icon near the "About" section to look for your printer model, error message, or specific repair topic. I receive dozens of questions asking whether we have videos about particular problems, and after creating repair videos for more than nine years, it is difficult to remember every video we have produced. YouTube's search function is usually the quickest way to locate relevant material, and it may also recommend useful videos from other repair channels.

Thank you again for taking the time to explain the symptoms in such detail and for supporting BCH Technologies. I hope the information above gives you a clearer direction for separating the original printing problem from the blank control-panel problem and deciding what to inspect next. We greatly appreciate your continued engagement with our repair content.