Circuit Description
The internal fault detection is handled inside the HVAC control module (IPM). No external circuits are involved.
Conditions for Running the DTC
The microprocessor runs the program to detect an internal fault when power up is commanded. The only requirements are voltage and ground. This program runs even if the voltage is out of the valid operating range.
Conditions for Setting the DTC
The microprocessor first writes information to a cell, or address, adds 0.25 to the value, calculates a check sum. If this check sum minus 0.25 is not equal to the cell value, the module sets the DTC.
Action Taken When the DTC Sets
The microprocessor refuses all additional inputs.
Conditions for Clearing the DTC
The DTC clears when the microprocessor makes a successful write to the EEPROM and check sum maneuver.
Diagnostic Aids
| • | This DTC may be stored as a history DTC with out affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module. |
| • | If this DTC is retrieved as both a current and history DTC, replace the module. |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views | |||
1 | Did you perform the HVAC Diagnostic System Check? | Go to Step 2 | |
2 |
Is the DTC current? | Go to Step 3 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems |
3 |
Important: Perform the recalibration procedure for the HVAC control module. Replace the IPM. Refer to HVAC Control Module Replacement . Did you complete the replacement? | Go to Step 4 | -- |
4 |
Does the DTC reset? | Go to Step 2 | System OK |
