Quick answer
Code 6 on a KeepRite furnace is an ignition proving failure: the flame sensor did not confirm a flame during the trial for ignition. The gas shuts off after each failed trial, and the control repeats the sequence three more times before ignition lockout (code 6 + 1). Confirm the manual gas shut-off at the furnace is open, cycle power once, and call if the code returns.
What code 6 means on a KeepRite furnace is narrow and specific: ignition proving failure. The control ran its lighting sequence and the flame sensor did not report a flame during the trial for ignition. That meaning comes from the status code chart in the ICP service manual for the F9MAE and G9MAE furnaces, the platform KeepRite shares with Tempstar and Heil. Codes vary by model, so the chart on the label inside your furnace door wins if it says something different.
What the control does after a failed trial for ignition
The gas shuts off on every failed trial. The control then repeats the ignition sequence three more times, and if no attempt proves a flame it moves to ignition lockout, shown as code 6 + 1. Four tries, then it stops.
That makes code 6 safe to leave alone while the furnace works through its attempts, because unburnt gas is not left flowing. What does not help is flipping the power switch again and again to force new tries. Let it lock out, take the one step below, and read how long a furnace lockout lasts if you are waiting on it.
The one safe step: check the gas shut-off, then cycle power once
- Find the manual shut-off valve on the gas pipe beside the furnace. A handle in line with the pipe is open; a handle across the pipe is closed.
- If it is closed and you know why (recent appliance work, a new tenancy, a summer shutdown), open it. If you cannot explain it, leave it closed and call.
- On a propane furnace, look at the tank gauge. Propane is the usual fuel on rural lots around Kilbride, Campbellville and rural Caledon where gas mains do not reach, and an empty tank produces the same failed ignition.
- Turn the furnace power switch off, count to 30, and turn it back on. Do this once.
- Watch one start through the viewing window in the furnace door, if your model has one, and note what you see. That observation is worth more to a technician than a second reset.
What you saw tells you which half of the problem it is
Burners that never light point to the gas side or the igniter. Burners that light, run for a few seconds and drop out point to the flame-proving side: the sensor or the ground. The code is the same in both cases, which is why the observation matters. The usual causes, most likely first:
- The gas valve or the manual shut-off is turned off. This is the common finding after any work on the gas line, and the only cause a homeowner can correct.
- A dirty or grounded flame sensor. Oxide builds up on the rod and blocks the small current the control uses to prove flame; a rod touching metal fails the same way.
- The green/yellow ground wire is not fastened to the furnace sheet metal. The flame signal returns through the cabinet, so a loose ground reads as no flame.
- A failed igniter. Gas flows, nothing lights it, and the trial ends without a flame.
When code 6 needs a technician, and what the repair costs
Call when the code returns after one power cycle, or when the light has moved to 6 + 1 more than once. The manual separates gas valve, igniter and flame-sensor faults with a component test, and that test is done with the burner compartment open and gas present. In Ontario that is work for a TSSA-licensed gas technician, not a homeowner.
If you smell gas at any point, skip all of this: leave the house and call your gas utility from outside.
- Service call and diagnosis: $90–$150, folded into the repair when you go ahead
- Flame sensor cleaning or replacement: $150–$300
- Hot surface igniter: $200–$450
- Gas valve: $500–$1,000
A closed valve or a loose ground wire has no part to price, so the technician tells you what the visit involves before starting. Bands for other furnace parts are on our pricing page, and every repair is quoted in writing before work begins.
ZK Mechanical services KeepRite furnaces from our Burlington shop across Oakville, Milton, Hamilton and Mississauga. For a code 6 that keeps returning, book furnace repair or send us the code and the model number from the rating plate. The KeepRite furnace error code guide covers the rest of the chart, and code 3 has its own page.