For 1990-2009 cars

Important: For the Auto HVAC diagnostic system check refer to the procedures following the diagnostic table.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step ensures that the battery, and the vehicle primary power and ground systems are functioning correctly.

2. Lack of communication may be due to a particular malfunction of a serial data circuit. The link to Scan Tool does not Communicate with Class 2 Device will provide a list of modules and the associated data network no communication diagnostic link.

3. A module that is operating in the incorrect power mode based on key position may cause other vehicle symptoms and/or DTCs to set. The link to Power Mode Mismatch will correct the condition before checking for module DTCs or symptoms.

4. This step ensures that all data link communication DTCs are diagnosed before system level DTCs.

5. This step ensures that all electronic control unit (ECU) internal DTCs are diagnosed before other system level DTCs.

6. This step ensures that all device voltage DTCs are diagnosed before other system level DTCs.

Step | Action | Yes | No
--- | --- | --- | ---
1 | Perform the following preliminary inspections:

• | Ensure that the battery is fully charged. Refer to Battery Inspection/Test .

• | Ensure that the battery cables are clean and tight.

• | Inspect for any open fuses.

• | Inspect the easily accessible systems or the visible system components for obvious damage or conditions that could cause the symptom.

• | Ensure that the grounds are clean, tight, and in the correct location.

• | Inspect for aftermarket devices that could affect the operation of the system. Refer to Checking Aftermarket Accessories .

• | Search for applicable service bulletins.

Did you find and correct the condition?

System OK

Go to Step 2

2 | Install a scan tool. Does the scan tool power up? | Go to Step 3 | Go to Scan Tool Does Not Power Up
3 |

1. Turn ON the ignition, with the engine OFF.
2. Attempt to establish communication with all of the control modules on the vehicle. Refer to Control Module References for the modules you should expect to observe.

Does the scan tool communicate with all of the expected vehicle control modules?

Go to Step 4

Go to Control Module References

4 | Important:

• | To ensure that retained accessory power (RAP) mode is inactive (if equipped), open the driver door during the following step.

• | The engine may start during the following step. Turn OFF the engine as soon as you have observed the crank power mode.

1. Access the ignition switch parameter on the scan tool.
2. Rotate the ignition switch, operate the ignition mode switch, through all positions while observing the switch parameter.

Does the parameter reading on the scan tool match the ignition switch position for all switch positions?

Go to Step 5

Go to Symptoms - Engine Electrical

5 | Attempt to start the engine. Does the engine crank? | Go to Step 6 | Go to Symptoms - Engine Electrical
6 | Attempt to start the engine. Does the engine start and idle? | Go to Step 7 | Go to Symptoms - Vehicle
7 | Important: Do not clear any DTCs unless instructed by a diagnostic procedure. Use the appropriate scan tool selections to obtain DTCs for each of the control modules. Does the scan tool display any DTCs? | Go to Step 8 | Go to Step 12
8 | Does the scan tool display any DTCs that begin with a "U"? | Go to Diagnostic Trouble Code (DTC) List - Vehicle | Go to Step 9
9 | Important: If any of these DTCs are displayed, diagnose them before diagnosing any other DTCs or symptoms. Does the scan tool display DTC B1000, B1001, B1004, B1007, B1009, B1013, C0550, P0601, P0602, P0603, P0604, P0605, P0606, P0607, P060D, P060E, P1600, P1621, P2107, P2108, or P2610? | Go to Diagnostic Trouble Code (DTC) List - Vehicle | Go to Step 10
10 | Important: If any of these DTCs are displayed, diagnose them before diagnosing any other DTCs or symptoms. Does the scan tool display DTC B1370, B1390, 1385, B1420, C0896, P0560, P0562, or P0563? | Go to Diagnostic Trouble Code (DTC) List - Vehicle | Go to Step 11
11 | Important: If any of the remaining DTCs are powertrain DTCs, select Capture Info in order to store the powertrain DTC information with a scan tool. If multiple DTCs are stored, diagnose the DTCs in the following order:

1. Component level DTCs, such as sensor DTCs, solenoid DTCs, and relay DTCs.
2. System level DTCs, such as misfire DTCs, evaporative emission (EVAP) system DTCs, and fuel trim DTCs.

Diagnose the remaining DTCs.

Go to Diagnostic Trouble Code (DTC) List - Vehicle

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12 | Is the customers concern with inspection/maintenance (I/M) testing? | Go to Explanation of Scheduled Services | Go to Symptoms - Vehicle

### Auto HVAC Diagnostic System Check

The fully automatic temperature controller (FATC) contains a self-diagnosis function to aid in finding any problem with the system. To enter the diagnostic mode, perform the following procedure:

1. Turn the ignition ON.
2. Set the temperature control to 26°C (79°F).
3. Within 3 seconds, push the AUTO and the OFF switches simultaneously, more than three times.
4. Count the number of times the temperature indicator screen blinks.
5. If there are no error codes set, the controller displays 00. When the controller indicates an error code, proceed to the table of that code.
6. Push the OFF switch to return the controller to its normal functions.