Goodman Furnace Code B1: Blower Motor Communication Fault (Meaning, Fixes)
What the code means
Goodman and Amana variable-speed furnaces (for example the *MVC96, *CVC96, *MVM97, *CVM97 and *MVS-U families) drive the circulator blower with an ECM motor that takes its commands from the integrated control module over a set of low-voltage control leads, while 115 V powers the motor through a separate plug. Goodman's troubleshooting chart describes b1 as "Integrated control module has lost communications with circulator blower motor." Its service manual says the control detects b1 from a bad ground or no communication to the blower motor. On a ComfortNet communicating thermostat the same fault shows as MOTOR COMM with the Call for Service icon and a scrolling Check Furnace message. b1 isn't a flame, venting or pressure-switch problem, and it isn't b0 (motor not running when it should be) or b2 (motor horsepower doesn't match the furnace's stored data), which are separate codes.
Likely causes
- A loose or disconnected wiring connection at the circulator motor control leads, the first thing Goodman's chart lists for b1
- A bad ground between the motor and the furnace control, which Goodman's service manual names as a way b1 is detected
- No 115 V power reaching the blower motor, or line voltage outside the 104 to 127 V range Goodman's flowchart checks for
- A failed circulator blower motor or its motor control module
- A failed integrated control module that isn't sending the low-voltage control signal to the motor
Safe DIY checks
Turn off power at the furnace/HVAC service switch and the breaker before opening panels. Shut the gas valve before any work near the burners, and never disconnect or alter the gas line. If you smell gas, leave the house and call your gas utility.
- Write down exactly what the display shows. A lowercase b followed by 1 is b1; if it reads b0, b2 or another b code, look that code up instead, since Goodman treats them differently.
- Turn the furnace off at its service switch or breaker, wait about a minute, and turn it back on with the blower door fully closed. The door switch cuts power to the motor when the door is off.
- With the power off, open the blower compartment and check that both plugs on the blower motor (the power plug and the smaller control plug) are pushed all the way in, and that the control harness is firmly seated at the furnace control board. Look for pinched, chafed or burned wires and a loose green ground wire.
- To see the fault history, use the left or right button on the control board until the display shows L6F (Last 6 Faults) and press the center button. Goodman stores the six most recent faults, newest first. Holding the center button for about 5 seconds in that menu clears the non-active faults, and the display flashes three times to confirm.
- If b1 comes back right away after the connections are reseated, leave the power off and call a technician. The furnace won't heat while the blower can't be controlled.
🛠 When to call a pro
- b1 returns after a power cycle and the plugs and ground are good. Goodman's flowchart has the tech check line voltage at the motor (104 to 127 VAC) and the low-voltage control signal from the board before blaming a part.
- Testing the ECM motor and its controller with an ECM tester and checking the windings for an open or short, then replacing the motor or controller if it fails.
- Replacing the integrated control module if the board isn't putting out the control voltage. Goodman's newer boards need the furnace's shared data from the memory card, so a matching board is required.
- You smell gas or a carbon monoxide alarm sounds. Leave the house and call your gas utility from outside.
Parts that commonly fix it
Always match the part number to your exact model.
ECM blower motor (exact OEM match for your model)
Only after a tech confirms power, ground and wiring are good and the motor won't respond. Variable-speed motors are programmed for the furnace model.
Search eBay →Furnace control board (exact OEM match)
Second suspect after the motor, per Goodman's chart.
Search eBay →Sources
- Goodman *MVS80*U & *CVS80*U Service and Troubleshooting RS6612019R3 (fault table: b1 = integrated control module has lost communications with circulator blower motor, furnace fails to operate, tighten wiring, check motor, check control; B0 & B1 flowchart: bad ground or no communication, 104-127 VAC motor supply, control voltage check, ECM tester; applicable *MVS-U, *CVC, *MVC, *CVM, *MVM; L6F last 6 faults, clearing faults, fault code recall)
- Goodman CVM96 installation instructions, troubleshooting chart (b1 = MOTOR COMM on ComfortNet thermostat, Call for Service icon, Check Furnace message; loose control leads, failed motor, failed control module; b0 and b2 rows) via ManualsOnline
Last reviewed 2026-10-23. Always confirm against the manual for your exact model number.