Tony Hwang wrote, on Tue, 23 Dec 2014 09:09:33 -0700:

I use O'scope to check flame sensor.

I always wanted an oscilloscope; but I don't have one.

If that is the problem, I'd just replace it.

Wouldn't you know it, but none of the service manuals have the
part numbers. I called Bryant and they said that both Bryant
and Payne use the same part numbers, but they didn't have a parts
list at their 800-428-4326x3 phone number.

They gave me four dealers to call, and all had messages, so,
I left a message with all four, hoping they'll get back to me
on the part number for the flame sensor and control board.

If furnace fired and soon after it quits probably sensor
did not sense the flame.

I agree.
The current conditions are classic for when the flame sensor
does not sense the flame (based on all that I've learned yesterday).

Isn't there a test point on the board when temporarily grounded
it will go thru logic steps of the operation.

Yes. But ...

The test is confusing (to me) as to what the correct procedure is.
Here's the test, on the bottom of page 10, of this manual:
http://dms.hvacpartners.com/docs/100...00/SP04-62.pdf

Here's what that test "says":
"To initiate the component test sequence,shut OFF the room
thermostat or disconnect the "R" thermostat lead. Briefly
short the TEST terminal to the Com 24V terminal. Status
LED will flash code and then turn ON the inducer motor.
The inducer motor will run for the entire component test.
The hot surface ignitor, blower motor-heat speed, and blower
motor-cool speed will be turned ON for 10-15 seconds each."

It's not clear which "R" needs to be disconnected, as there
is are two "R" wires at the thermostat, and one "R" wire at
the control board. I disconnected both.

Then I attached an orange wire to the "COM" terminal and
briefly touched the "TEST" spade on the control board.

Nothing happened.

I then turned on the power, and nothing happened when I did that.
I then turned on the power and held down the door switch, and,
this time "something" happened - but the results were confusing.

First the inducer motor went on (as expected), and then the
igniter lit brightly (as expected) and then nothing was visibly
happening until the inducer went off, about a minute or so
thereafter.

OK. I "think" I ran the test. What did it do?
I don't know.

What did it tell me?
I don't even know what to look for.

I believe all Carrier board has it and Bryant is Carrier 2nd tier
product. Control board is quite common amongst brands. My cabin Trane
furnace has Carrier equivalent board in there. Furnace operation is just
a simple one line yes/no logic flow.

I called Bryant who said that Carrier and Payne and Bryant are all
owned by the same company, and that Payne & Bryant are parts
compatible.