Ruud U96VA0702317MSA Error Code d4: No Valid Model Data on Memory Card
What Does Code d4 Mean?
Code d4 on the Ruud U96VA0702317MSA tells you the memory card in connector P6 of the Integrated Furnace Control cannot be read — it is corrupt, blank, or absent — yet the furnace continues to run normally. That is possible because a valid copy of the model data also lives in the board's microprocessor, so the variable-speed blower still has a correct operating map to follow.
This is why d4 is a low-severity, standby-mode notice rather than a shutdown. Contrast it with code d1, where there is no valid data anywhere and the furnace cannot operate at all, and with code d6, where the card is readable but its stored horsepower disagrees with the installed motor. With d4 the furnace is fine for now; the card is simply the part that is out of service.
The card should still be replaced so the board keeps a good external backup. The replacement must be the correct card for this specific model and BTU rating — never a card borrowed from another furnace, condenser, or air handler, because mismatched data can drive the blower incorrectly and, over time, damage the heat exchanger.
What You'll Notice
- The IFC shows d4, typically only while the furnace is in standby
- Heating, cooling, and fan all continue to work normally despite the code
- The fault commonly appears after a card was removed, swapped, or left out during service
- The code persists until the correct memory card is installed
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Corrupt or blank memory card | Most common | ✗ Call a pro → |
How This Is Diagnosed
A technician confirms the furnace is still operating (which distinguishes d4 from the total shutdown of d1), then inspects connector P6 to see whether a card is present and whether it is the correct one for this model.
They order and install the correct model- and BTU-specific replacement card, avoiding any card from another unit, and cycle power so the board reads the new data. They then verify the d4 notice has cleared and staging is normal.
When to Call a Professional
This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:
- The d4 notice keeps appearing in standby and you want the backup card restored
- The memory card was removed or swapped during a previous repair and never replaced with the correct part
- You are unsure whether the installed card actually matches this furnace model and BTU rating
Frequently Asked Questions
Do I need to fix code d4 right away if the furnace still heats?
It is not an emergency because the control runs on its internal backup, but the correct card should be replaced so a good external copy of the model data exists again.
Can I use a memory card from another furnace to clear d4?
No. Using a card from a different furnace or component can make the blower run incorrectly and may damage the heat exchanger; only the correct card for this model and BTU rating should be used.
✓ Verified against manufacturer service manual — March 2026