Diagnostic Aids - HVAC System - Automatic

The diagnostic aids include the history and current trouble codes and the related diagnostic tables.
^ The following conditions may result in an intermittent operation of the heater-A/C control with no Diagnostic Trouble Codes (DTCs) stored:
- Any condition which results in the interruption of power to the heater-A/C control
- Out of range battery or ignition voltage specification. Normal battery or ignition voltage: 9 V-16 V
- A loose or damaged ground(s)
- An open or short in the Class 2 serial data link
^ An intermittent failure in the electronic system may be very difficult to detect and accurately diagnose. The heater-A/C control tests for different malfunctions under different vehicle conditions. A thorough test drive is often needed in order to repeat a fault condition. If the system malfunction is not repeated during the test drive, a good description of the complaint may be very useful in locating an intermittent fault condition. Faulty electrical connections or wiring cause most intermittent problems. When an intermittent condition is suspected, check the suspected circuits for the following conditions:
- Poor mating of connector halves or backed out terminals
- Improperly formed or damaged terminals
- Wire chafing
- Poor wire-to-terminal connections
- Dirty wire-to-terminal connections
- Dirty or corroded terminals
- Damage to connector bodies
^ Use the J 35616-A whenever a diagnostic procedure requests probing or checking a terminal. Using this adapter ensures that no damage to the terminal will occur and indicates whether the contact tension is sufficient.
^ Use the scan tool in order to read the DTCs set by the system. Refer to Scan Tool. If the DTC is a history DTC, the problem may be intermittent. Perform the tests shown while moving the related wiring and connectors. This often causes the malfunction to occur. Perform a thorough inspection of all related wiring and connectors pertaining to the history DTC stored. Refer to Intermittents and Poor Connections for more information. Intermittents and Poor Connections
^ Exit all of the scan tool tests before cycling the ignition switch from the off position to the on position unless you are directed otherwise. Follow the operating instructions in the scan tool user manual. Failure to follow these instructions may set DTCs, cause vehicle system malfunctions, set false DTCs, or cause scan tool malfunctions.
^ Inspect all relative fuses (see schematic) for the heater-A/C control. If the fuses are open, inspect the circuits which are fed power by these fuses for a short to ground.
^ Ensure that all relative grounds are clean and tight.
^ For heater-A/Control service procedures, refer to Control Assembly Replacement (CJ2).
^ Inspect for a broken (or partially broken) wire inside of the insulation. A broken (or partially broken) wire may cause a system malfunction but prove good in a continuity/voltage check with a system disconnected. These circuits may be intermittent or resistive when loaded, and if possible, should be checked by monitoring for a voltage drop with the system operational (under load).
^ Inspect for proper installation of the aftermarket electronic equipment. Improper installation may affect the integrity of other systems.