HP Officejet Pro 8600 Carriage Jam After Encoder Strip and Carriage Replacement

Question:
After replacing the encoder strip on an HP Officejet Pro 8600, the printer still reports a "carriage jam" error. The machine was fully reassembled for testing, new ink cartridges were installed, and even an additional carriage assembly was tried. Despite this, the carriage does not move during startup, though the printer can still scan and connect to wireless networks. What could be causing this persistent error?

Answer:

Possible Causes After Encoder Strip Replacement

1. Encoder Strip Alignment or Damage
   Even if cleaned and visually transparent, the encoder strip must be perfectly aligned and securely seated in its track. A slight misalignment or micro-damage (tiny scratches, bends, or residue) can prevent the optical sensor on the carriage from reading position data, leading to a "Carriage Jam" error (0x610000f6 or 0x6100004a are standard error codes).

2. Carriage Motor or Belt Issues

   • If the carriage doesn't move at all during startup, the carriage drive motor may not be engaging.

   • The timing belt that connects the carriage to the motor may be loose, broken, or improperly tensioned.

   • If the motor spins but the carriage does not move, the pulley or belt connection may be slipping.

3. Sensor Malfunction

   • The optical sensor that reads the encoder strip may be dirty, damaged, or misaligned.

   • In some cases, debris or ink overspray builds up inside the sensor window, preventing accurate reading.

   • If the printer detects no feedback from this sensor, it assumes the carriage is stuck and triggers a jam error.

4. Carriage Path Obstruction
   Even after reassembly, check the entire rail and surrounding area for dried ink chunks, loose screws, or small plastic pieces. Sometimes reassembly introduces new obstructions that aren't obvious at first glance.

5. Mainboard or Logic Board Failure

   • Since the printer can still scan and connect wirelessly, the system board is partially functional.

   • However, a failure in the carriage control circuit (motor driver chip) can stop movement entirely while still allowing other functions to operate.

   • This is a less common but possible cause, especially if multiple replacement parts haven't resolved the issue.

Recommended Next Steps

• Recheck Encoder Strip Installation: Ensure it is installed straight and taut, seated evenly on both ends without twists.

• Inspect Carriage Belt: Verify it is not frayed, slipping, or misaligned. A belt that jumps teeth will prevent carriage motion.

• Clean Carriage Sensor: Use a cotton swab and isopropyl alcohol to carefully clean the sensor slot on the carriage where the strip passes through.

• Run a Power Reset: Disconnect power, wait 60 seconds, and plug back in. Sometimes the firmware clears errors after a hard reset.

• Test With Known-Good Parts: Since you've already tried a second carriage, the next suspect would be the carriage motor assembly or mainboard.

If none of these resolve the issue, the error may point to a failing logic board, which typically repairs less cost-effective compared to replacing the printer.

Addressing printer issues can be complicated because they often require hands-on testing and part swapping. For this reason, we're not able to provide remote repair or troubleshooting. We do, however, offer an in-person diagnostic service through our printer repair facility (https://bchtechnologies.com/printer-repair-service). Please note this service operates on a first-come, first-served basis, and it may take a few weeks before your printer can be inspected. While our rates may not be the lowest, we handle either complete printer repairs or targeted part-level fixes.

We encourage you to also explore self-help resources, starting with our YouTube channel (https://youtube.com/@bchtechnologies). Use the search tool on the channel's homepage to find videos about carriage jams, encoder strip installation, or belt replacements. YouTube may also recommend related content from other technicians that could help.

Thank you again for your patience and for sharing your detailed observations. Your input helps us improve our resources for all printer users.