Diagnostic Aids
WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
- A damaged or broken air temperature actuator or mode door can cause this DTC to set.
- If the condition is not present refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
DTC B0408 or B0418
| Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
| Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views |
||||
| 1 | Did you review the HVAC operation and perform the necessary inspections? | - | Go to Step 2 | Go to Diagnostic System Check - HVAC Systems - Automatic |
| 2 |
|
- | Go to Step 3 | Go to Step 4 |
| 3 | Inspect the air temperature actuator for the following:
Did you find and correct the condition? |
- | Go to Step 15 | Go to Diagnostic Aids |
| 4 | Test the ignition 3 voltage circuit of the air temperature actuator for an open or a high resistance. Refer to Circuit Testing
or Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 15 | Go to Step 5 |
| 5 | Test the ground circuit of the air temperature actuator for an open. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 15 | Go to Step 6 |
| 6 | Test the 5 volt reference circuit of the air temperature actuator for an open, a high resistance, short to ground, or a short to voltage. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 15 | Go to Step 7 |
| 7 | Test the air temperature position signal circuit of the air temperature actuator for an open, a high resistance, short to ground, or a short to voltage. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 15 | Go to Step 8 |
| 8 | Test the air temperature control circuit of the air temperature actuator for an open, a high resistance, short to ground, or a short to voltage. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 15 | Go to Step 9 |
| 9 |
IMPORTANT:
The air temperature actuator connector and the HVAC controller connector must be connected to correctly perform the test.
|
- | Go to Step 10 | Go to Step 11 |
| 10 |
|
0 V decreasing 5 V increasing 2.5 V stationary |
Go to Step 11 | Go to Step 12 |
| 11 | Inspect for poor connections at the harness connector of the air temperature actuator. Refer to Testing for Intermittent Conditions and Poor Connections
and Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 15 | Go to Step 13 |
| 12 | Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections
and Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 15 | Go to Step 14 |
| 13 | Replace the air temperature actuator. Refer to Air Temperature Actuator Replacement - Left or Air Temperature Actuator Replacement - Right . Did you complete the replacement? |
- | Go to Step 15 | - |
| 14 | Replace the HVAC control module. Refer to HVAC Control Module Replacement . Did you complete the replacement? |
- | Go to Step 15 | - |
| 15 | Operate the system in order to verify the repair. Did you correct the condition? |
- | System OK | Go to Step 2 |