HVAC

B210A-SYSTEM VOLTAGE LOW







Theory of Operation

The A/C Heater Control constantly monitors battery and ignition voltage to ensure proper operation. If the voltage to the controller is out of range it could cause damage to the controller or its respective components. If the voltage of either circuit drops below or rises above a predetermined calibration a Diagnostic Trouble Code (DTC) will set.

- When Monitored:
With the ignition on.

- Set Condition:
If the controller battery voltage is less than or equal to 10.0 volts for period of 5.0 seconds.





Always perform the HVAC Pre-Diagnostic Troubleshooting procedure before proceeding. HVAC Pre-Diagnostic Troubleshooting Procedure.

1. CHECK FOR CHARGING SYSTEM DTCS
1. Using the scan tool, read PCM DTCs.

Are there any charging system DTCs present in the Powertrain Control Module (PCM)?

Yes

- Testing and Inspection Perform the appropriate diagnostic procedure.

No

- Go To 2

2. CHECK FOR TOTALLY INTEGRATED POWER MODULE DTCS
1. Using the scan tool, read TIPM DTCs.

Are there any TIPM DTCS present?

Yes

- Testing and Inspection Perform the appropriate diagnostic procedure.

No

- Go To 3

3. CHECK IF THE DTC IS ACTIVE
1. Using the scan tool, read HVAC DTCs.

Is this DTC active?

Yes

- Go To 4

No

- Go To 7

4. CHECK THE (F921) FUSED RUN RELAY OUTPUT CIRCUIT FOR AN OPEN




1. Ignition on, engine not running.
2. While back probing, measure the voltage of the (F921) Fused Run Relay Output circuit in the A/C Heater Control C1 harness connector.

Is the voltage 10.0 volts or below?

Yes

- Repair the (F921) Fused Run Relay Output circuit for an open or high resistance.NOTE: If the fuse is open, make sure to check for a short to ground on the (F921) Fused Run Relay Output circuit.

- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Go To 5

5. CHECK THE (A417) FUSED B(+) CIRCUIT FOR AN OPEN




1. Ignition on, engine not running.
2. While back probing, measure the voltage of the (A417) Fused B(+) circuit in the A/C Heater Control C1 harness connector.

Is the voltage 10.0 volts or below?

Yes

- Repair the (A417) Fused B(+) circuit for an open or high resistance.NOTE: If the fuse is open, make sure to check for a short to ground on the (A417) Fused B(+) circuit.

- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Go To 6

6. CHECK THE (Z912) GROUND CIRCUIT FOR AN OPEN




1. Turn the ignition off to the lock position.
2. Disconnect the A/C Heater Control C1 harness connector.
3. Using a 12-volt test light connected to 12-volts, check the (Z912) Ground circuit.

NOTE: The test light must illuminate brightly. Compare the brightness to that of a direct connection to the battery.

Does the test light illuminate brightly?

Yes

- Replace and program the A/C Heater Control.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Repair the (Z912) Ground circuit for an open.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

7. CHECK THE WIRING AND CONNECTORS
1. The conditions necessary to set the DTC are not present at this time.
2. Using the scan tool, check the Environmental Data to help identify the conditions in which the DTC was set.
3. 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.
4. 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. HVAC Verification Test.

No

- Test complete.