Automatic Temperature Control
B1028-Rear Blower Control Request Input Circuit Low
For a complete wiring diagram, refer to.
Theory of Operation
The Rear A/C Heater Control works in conjunction with the A/C Heater Control to control the rear blower motor, rear temperature control and rear mode control. The Rear A/C Heater Control is constantly monitored by the A/C Heater Control for proper operation. If the monitored signal circuits are out of a calibrated range a DTC will set.
• When Monitored: With the ignition on.
• Set Condition: If the A/C Heater Control detects a voltage less than 0.23 of a volt for 60 seconds on the Rear Blower Signal circuit. If a valid voltage is detected for two seconds the DTC will change from active to stored and stay in the controllers memory for 100 consecutive ignition cycles.
Always perform the HVAC Pre-Diagnostic Troubleshooting procedure before proceeding. Refer to => Non-DTC Based
Diagnostics. HVAC Pre-Diagnostic Troubleshooting Procedure
Test Step 1 - VERIFY THE DTC IS ACTIVE
• Ignition on, engine not running.
• With the scan tool, erase HVAC DTCs.
• Turn the ignition off, wait 10 seconds, and turn the ignition on.
• Make sure the Rear Control Lockout on the A/C Heater Control is not turned on.
• After waiting a minimum of 60 seconds, read HVAC DTCs.
Does the scan tool display this DTC as active?
Yes
• Go to Test Step 2 => [ Test Step 2 - CHECK FOR OTHER REQUEST CIRCUIT LOW DTCS ]
No
• Go to Test Step 9 => [ Test Step 9 - CHECK THE WIRING AND CONNECTORS ]
Test Step 2 - CHECK FOR OTHER REQUEST CIRCUIT LOW DTCS
• With the scan tool, read HVAC DTCs.
Does the scan tool also display the DTCs B102E-Rear Blend Request Input Circuit Low and B113D-Rear Mode Request Low as active?
Yes
• Go to Test Step 3 => [ Test Step 3 - CHECK THE REAR A/C HEATER CONTROL CONNECTOR ]
No
• Go to Test Step 6 => [ Test Step 6 - CHECK THE (C11) REAR BLOWER SIGNAL CIRCUIT FOR A SHORT
TO GROUND ]
Test Step 3 - CHECK THE REAR A/C HEATER CONTROL CONNECTOR
• Check if the Rear A/C Heater Control harness connector is unplugged or not fully seated.
• Check the Rear A/C Heater Control and harness connector for pushed out, damaged, corroded pins or terminals.
Were there any problems found?
Yes
• Repair as necessary.
• Perform the HVAC Verification Test. Refer to => Non-DTC Based Diagnostics. HVAC Verification Test
No
• Go to Test Step 4 => [ Test Step 4 - CHECK THE (C800) 5 VOLT SUPPLY CIRCUIT FOR A SHORT
TO GROUND ]
Test Step 4 - CHECK THE (C800) 5 VOLT SUPPLY CIRCUIT FOR A SHORT TO GROUND
• Turn the ignition off to the lock position.
• Disconnect the A/C Heater Control harness connector.
• Disconnect the Rear A/C Heater Control C1 harness connector.
• Measure the resistance between ground and the (C800) 5 Volt Supply circuit.
Is the resistance below 100k Ohms?
Yes
• Repair the (C800) 5 Volt Supply circuit for a short to ground.
• Perform the HVAC Verification Test. Refer to => Non-DTC Based Diagnostics. HVAC Verification Test
No
• Go to Test Step 5 => [ Test Step 5 - CHECK THE (C800) 5 VOLT SUPPLY CIRCUIT FOR AN OPEN ]
Test Step 5 - CHECK THE (C800) 5 VOLT SUPPLY CIRCUIT FOR AN OPEN
• Measure the resistance of the (C800) 5 Volt Supply circuit between A/C Heater Control harness connector and the Rear A/C Heater Control C1 harness connector.
Is the resistance below 1.0 Ohm?
Yes
• Go to Test Step 8 => [ Test Step 8 - CHECK THE HVAC CONTROL MODULES ]
No
• Repair the (C800) 5 Volt Supply circuit for an open or high resistance.
• Perform the HVAC Verification Test. Refer to => Non-DTC Based Diagnostics. HVAC Verification Test
Test Step 6 - CHECK THE (C11) REAR BLOWER SIGNAL CIRCUIT FOR A SHORT TO GROUND
• Turn the ignition off to the lock position.
• Disconnect the A/C Heater Control harness connector.
• Disconnect the Rear A/C Heater Control C1 harness connector.
• Measure the resistance between ground and the (C11) Rear Blower Signal circuit.
Is the resistance below 100k Ohms?
Yes
• Repair the (C11) Rear Blower Control Signal circuit for a short to ground.
• Perform the HVAC Verification Test. Refer to => Non-DTC Based Diagnostics. HVAC Verification Test
No
• Go to Test Step 7 => [ Test Step 7 - CHECK THE (C11) REAR BLOWER SIGNAL CIRCUIT FOR AN OPEN ]
Test Step 7 - CHECK THE (C11) REAR BLOWER SIGNAL CIRCUIT FOR AN OPEN
• Measure the resistance of the (C11) Rear Blower Signal circuit between A/C Heater Control harness connector and the Rear A/C Heater Control C1 harness connector.
Is the resistance below 1.0 Ohm?
Yes
• Go to Test Step 8 => [ Test Step 8 - CHECK THE HVAC CONTROL MODULES ]
No
• Repair the (C11) Rear Blower Signal circuit for an open or high resistance.
• Perform the HVAC Verification Test. Refer to => Non-DTC Based Diagnostics. HVAC Verification Test
Test Step 8 - CHECK THE HVAC CONTROL MODULES
• Reconnect the A/C Heater Control harness connector.
• Ignition on, engine not running.
• With the scan tool, erase HVAC DTCs.
• Turn the ignition off to the lock position.
• Connect a jumper wire between the (C800) 5-volt Supply circuit and the (C11) Rear Blower Signal circuit in the Rear A/C Heater Control C1 harness connector.
• Ignition on, engine not running.
• After waiting a minimum of 60 seconds, with the scan tool, read HVAC DTCs.
Does the scan tool display this DTC as active?
Yes
• Replace the A/C Heater Control.
• Perform the HVAC Verification Test. Refer to => Non-DTC Based Diagnostics. HVAC Verification Test
No
• Replace the Rear A/C Heater Control.
• Perform the HVAC Verification Test. Refer to => Non-DTC Based Diagnostics. HVAC Verification Test
Test Step 9 - CHECK THE WIRING AND CONNECTORS
• The conditions necessary to set the DTC are not present at this time.
• With the scan tool, check the Environmental Data to help identify the conditions in which the DTC was set.
• Using the wiring diagrams as a guide, check all related splices and connectors for signs of water intrusion, corrosion, pushed out or bent terminals, and correct pin tension.
• Wiggle the wiring and connectors while checking for shorted and open circuits.
Were there any problems found?
Yes
• Repair as necessary.
• Perform the HVAC Verification Test. Refer to => Non-DTC Based Diagnostics. HVAC Verification Test
No
• Test complete.