Ford Mustang (1999-2004) Service Manual: Inspection and Verification

1. Verify the customer's concern by operating the climate control system to duplicate the condition.

2. Inspect to determine if one of the following mechanical or electrical concerns apply:

Visual Inspection Chart

a - A leak in the vacuum control circuit may occur during acceleration (slow leak), at all times (large leak), or only when specific functions are selected (indicating a leak in that portion of the circuit). The vacuum hoses used in the passenger compartment control circuit are constructed from PVC plastic material. The vacuum hoses used in the engine compartment are constructed of Hytrel. Because of the materials used, never pinch the vacuum hoses off during diagnosis to locate a leak. A wood golf tee can be used as a plug when it is necessary to plug one end of a vacuum hose for leak test purposes.

3. If the inspection reveals obvious concerns that can be readily identified, repair as required.

4. If the concern remains after the inspection, connect the scan tool to the data link connector (DLC) located beneath the instrument panel and select the vehicle to be tested from the scan tool menu. If the vehicle selection cannot be entered:

• check that the program card is correctly installed.
• check the connections to the vehicle.
• check the ignition switch position.

If the scan tool still does not allow the vehicle selection to be entered, refer to the scan tool manual.

5. Carry out the DATA LINK DIAGNOSTIC TEST using the scan tool. If the scan tool responds with:

• CKT 914, CKT 915 or CKT 70 = ALL MODULE NO RESPONSE/NOT EQUIPPED, go to Communication System Diagnostics in Section to diagnose network concern.
• If the powertrain control module (PCM) is not listed for a communication concern, turn the A/C function selector switch to OFF and execute self-test diagnostics for the PCM.

6. If any PCM DTCs are retrieved, and are related to the concern, go to the Powertrain Control Module Diagnostic Trouble Code (DTC) Index to continue diagnostics.

7. If no DTCs related to the concern are retrieved, go to the Symptom Chart to continue diagnostics.

Powertrain Control Module Diagnostic Trouble Code (DTC) Index