Masterbuilt Charcoal Grill Err 4 — What It Means & How to Fix It
Err 4 on a Masterbuilt Gravity Series 600 means the charcoal failed to ignite, and the manual gives a five-point checklist before you restart.
What this code means
Masterbuilt lists the cause as "Charcoal failed to ignite". The fan can only bring the fire up if air can pass through the hopper, so the manual's checks are all about airflow and fuel: shutdown slides removed, hopper lid and ash door fully closed, charcoal in the hopper, and an ash grate that is not blocked with old ash.
Masterbuilt's manual for the Gravity Series 600 (model MB20041023) lists "Err 4" in its troubleshooting table with this meaning. Masterbuilt's other grills and smokers have their own tables, so check the manual for your model number.
Most likely causes
| Cause | How likely | DIY-fixable? |
|---|---|---|
| Shutdown slides left in place | Very common | Yes — no tools |
| Ash grate blocked with ash from the last cook | Common | Yes — shake the grate |
| Hopper lid or ash door not fully closed | Common | Yes — no tools |
| Hopper out of charcoal | Occasional | Yes — refill |
What you can try yourself
- Make sure both shutdown slides have been removed.
- Check that the hopper lid and the ash door are fully closed and latched.
- Confirm there is charcoal in the hopper.
- Shake the ash grate so old ash and spent charcoal fall through and stop blocking it.
- Restart the grill.
When to call a technician
- The charcoal still will not light with all five checks done.
- The fan does not run at all during startup.
Typical professional repair cost: Free — every check in the manual is something the owner does without tools.
Frequently asked questions
Why won't my Masterbuilt Gravity Series light?
Err 4 usually comes down to airflow. Remove the shutdown slides, close the hopper lid and ash door properly, and shake the ash grate clear before relighting.
What are the shutdown slides for?
They close off the hopper to put the fire out at the end of a cook. Left in place at startup, they stop the charcoal from igniting.
Sources checked
Error meanings can vary by model. This guide was checked against the documentation above; use the manual for the model number on your own appliance when it differs.
Related Masterbuilt codes
- Masterbuilt Charcoal Grill Err 1 Err 1 on a Masterbuilt Gravity Series 600 means the grill's temperature probe is not fully plugged in to the controller.
- Masterbuilt Charcoal Grill Err 2 Err 2 on a Masterbuilt Gravity Series 600 means a meat probe has malfunctioned, and the manual sends you to Masterbuilt Customer Service.
- Masterbuilt Charcoal Grill Err 3 Err 3 on a Masterbuilt Gravity Series 600 means the grill has overheated, and the manual names a grease fire or a fan malfunction as the things to look for.
- Masterbuilt Charcoal Grill Err 5 Err 5 on a Masterbuilt Gravity Series 600 means a meat probe is reading above 300°F — hotter than it is meant to measure.
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