DTC Troubleshooting: B2991
DTC B2991:
 Heater Control Unit Lost Communication with Audio HVAC Subdisplay Unit (with audio system) or HVAC Subdisplay Unit (without audio system)
  1. Clear the DTC with the HDS.
  1. Turn the ignition switch OFF and then ON(II).
  1. Check for DTCs.
Is DTC B2991 indicated?
YES -
Go to Step 5 .
NO -
Intermittent failure, check for loose wires or poor connections on the audio HVAC subdisplay unit or HVAC subdisplay unit and heater control unit circuit.■
  1. Turn the ignition switch OFF.
  1. Disconnect the heater control unit 32P connector.
  1. Disconnect audio HVAC subdisplay unit connector E (5P) (with audio system) or the HVAC subdisplay unit 10P connector (without audio system).
  1. Check the continuity between the following terminals of the heater control unit 32P connector and audio HVAC subdisplay unit connector E (5P) (with audio system) or the HVAC subdisplay unit 10P connector (without audio system).
Is there continuity?
YES -
Go to Step 9 .
NO -
Repair open in the wire(s) between the heater control unit and the audio HVAC subdisplay unit (with audio system) or the HVAC subdisplay unit (without audio system).■
  1. Check for continuity between body ground and audio HVAC subdisplay unit connector E (5P) terminals No. 4 and No. 5 individually (with audio system) or between body ground and the HVAC subdisplay unit 10P connector terminals No. 4 and No. 5 individually (without audio system).
Is there continuity?
YES -
Repair short to body ground in the wire(s) between the heater control unit and the audio HVAC subdisplay unit (with audio system) or the HVAC subdisplay unit (without audio system).■
NO -
Go to Step 10 .
  1. Reconnect the heater control unit 32P connector.
With audio system
Without audio system
  1. Connect audio HVAC subdisplay unit connector E (5P) terminals No. 4 and No. 5 with a jumper wire (with audio system) or the HVAC subdisplay unit 10P connector terminals No. 4 and No. 5 with a jumper wire (without audio system).
  1. Turn the ignition switch ON (II).
  1. Press the RECIRCULATION CONTROL and OFF buttons.
Does the rear window defogger or recirculation control indicator turn on?
YES -
Substitute a known-good audio HVAC subdisplay unit (with audio system) or HVAC subdisplay unit (without audio system), and recheck. If the symptom goes away, replace the original audio HVAC subdisplay unit (with audio system) or HVAC subdisplay unit (without audio system).■
NO -
Substitute a known-good heater control unit, and recheck. If the symptom goes away, replace the original heater control unit .■
With audio system
Without audio system