Automatic Temperature Control
B113D-Rear Mode Request 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 0.21 of a volt for 60 seconds on the Rear Mode Signal circuit. If a valid voltage is detected for 2 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 REAR REQUEST CIRCUIT LOW DTCS ]
No
• Go to Test Step 9 => [ Test Step 9 - CHECK THE WIRING AND CONNECTORS ]
Test Step 2 - CHECK FOR OTHER REAR REQUEST CIRCUIT LOW DTCS
• With the scan tool, read HVAC DTCs.
Does the scan tool also display the DTCs B1028-Rear Blower Control Request Input Circuit Low and B102E-Rear Blend 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 (C53) REAR MODE 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 SHORT TO
GROUND ]
Test Step 4 - CHECK THE (C800) 5 VOLT SUPPLY CIRCUIT FOR 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 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 the A/C Heater Control harness connector and the Rear A/C Heater Control 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.
• Perform the HVAC Verification Test. Refer to => Non-DTC Based Diagnostics. HVAC Verification Test
Test Step 6 - CHECK THE (C53) REAR MODE 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 harness connector.
• Measure the resistance between ground and the (C53) Rear Mode Signal circuit.
Is the resistance below 100k Ohms?
Yes
• Repair the (C53) Rear Mode 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 (C53) REAR MODE SIGNAL CIRCUIT FOR AN OPEN ]
Test Step 7 - CHECK THE (C53) REAR MODE SIGNAL CIRCUIT FOR AN OPEN
• Measure the resistance of the (C53) Rear Mode Signal circuit between A/C Heater Control harness connector and the Rear A/C Heater Control 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 (C53) Rear Mode 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
• Ignition on, engine not running.
• With the scan tool, erase HVAC DTCs.
• Turn the ignition off to the lock position.
• Reconnect the A/C Heater Control harness connector.
• Connect a jumper wire between the (C800) 5-volt Supply circuit and the (C53) Rear Mode Signal circuit in the Rear A/C Heater Control 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.