ACC 2 TROUBLESHOOTING

[9000]

ACC II will allow the owner to run a calibration and diagnostic mode. However, it will not display the actual codes, just the number of them present. A little applied logic can pinpoint a course of diagnostic action however. The calibration should be carried out whenever a problem arises or the battery has been disconnected or discharged. Note all the symptoms you can when a problem arises and they will help you decide what could be the root of the problem. Distinguish if the problem only occurs in AUTO mode, but goes away when you select the settings manually. If the problems exist in both modes, suspect the problem to be either in the motors running the various flaps or mechanical in origin. If the problem exists in AUTO only, suspect a sensor problem. Suspect the ECU only when all other diagnostics show no problem.

Run the diagnostic mode by having the engine running and pressing AUTO and <=> (Vent) at the same time. "0" should display in the ACC panel and will remain there until the sequence is completed. If the previously selected temperature returns to the display, the system has successfully calibrated itself and found no faults. If a single digit number is displayed, that is the number of faults in the system.

Always check for power and ground to the ACC unit. Never measure resistances with the ACC control unit plugged in. Never unplug the ACC unit with the key on. Make all measurements from the backside of the pin connectors to prevent damage to the small pins. Make sure all connectors are clean and fit together tightly. Look for pins that are pushed back in their connectors. Read all procedures thoroughly and follow any warnings they may give.

Access to the ECU and its connectors is easily achieved by removing the ashtray and reaching up and behind the ACC unit and popping it out. Unplug the unit only with the key off. The various sensors and motors in the interior are accessed by removal of the glove box. The components in the engine compartment are accessed by removing

ACC II Component Locations

ACC II Wiring Diagram

ACC II Wiring Component Locations

ACC II Programming

ACC II Limp Home Defaults (Use as starting point to determine a problem when output temperature is a problem)

ACC II Power Checks

ACC II Sensor Ground Faults Page 1

ACC II Sensor Ground Faults Page 2

ACC II Fan and Transistor Unit

The controller is located on the evaporator box, under the right plastic cover in the engine compartment near the windshield. There will be two similar connectors, one to the controller, one to the receiver drier pressure switch. On 88- cars the connector goes directly to the controller, there is no "pigtail" off the controller. You may have to remove the false bulkhead partition to get to the connector. One 12 mm bolt on the right side and one 25 Torx screw on the left side holds it down. It fits in a groove rather snugly and may take a bit of force to pull up. All the controllers sit down in the evaporator, held by four 10 Torx screws. They are black boxes about 4" X 4" in size. No need to remove the actual controller, just its connector to test.

ACC II Fan and Transistor Unit Page 1

ACC II Fan and Transistor Unit Page 2

To Service Bulletin To Check Transistor For Overheating

ACC II Sensors

Mixed Air Temp Sensor

Inside Temp Sensor or Inside Temp Sensor Fan Motor

Outside Temp Sensor

Solar Sensor

ACC II Motors

The motors the ACC II system use are stepper motors. They are much more reliable than their predecessors. If they exhibit a problem, you might try spraying them with a good contact cleaner before condemning them. Make sure they are securely attached to their mounts, many times they can work loose. Lactate on their mounting screws can help the problem. Pay close attention to the pins in the connectors going to them, they can spread open or get pushed back in the connector and make intermittent contact. Tightening and cleaning the pins solves a lot of problems as well.

Before removing a distribution drum motor, make sure the climate control is set to HI and the key turned on in order for the system to position the flaps at this setting. Otherwise, you will experience difficultly reinstalling the motor. if a new motor is to be fitted, Plug it into the connector and turn the key on with the temp selected to HI to run it to a position where it will be easier to install.