[Meerkat]

Note: The diagnostic function of the ATC/AZC system is lost when the vehicle's battery is disconnected. If you are going to disconnect the battery, first perform these diagnostic procedures.
1. Some Grand Cherokee models are equipped with automatic heating and air conditioning systems. 1998 and earlier models are equipped with Automatic Temperature Control systems and the 1999 and later models are equipped with the Automatic Zone Control system. In either case, these systems include a digital display on the dash panel. This system incorporates an on-board diagnostic function capable of troubleshooting input and output circuits and indicating both current and historical faults. Historical faults are those circuits which have had a problem in the past but are currently working. Many historical faults are the result of loose wiring connectors or connectors that have been disturbed by other repair work.
2. The same portion of the display that incidates the temperature acts as a test indicator to show fault codes.
3. If there is trouble in the ATC/AZC system, an "ER" message will display on the indicator once during an ignition cycle.
4. To access the fault codes, depress the AC and RECIRC buttons at the same time and hold them in while you rotate the temperature knob one click clockwise. Note: On 1999 and later models rotate the left temperature control knob one click clockwise. The complete display wil light up (the segment test). If any of the lighted segments of the flourescent vacuum tubes fail to illuminate, the ATC/AZC control panel is faulty and should be replaced.
5. After the segment test is performed release the buttons. On 1999 and later models, the display will clear momentarily and automatically begin displaying any stored trouble codes. If no trouble codes are stored a "0" will be displayed.
6. On 1998 and earlier models, "00" will show on the display (select test level). Now push either the AC or RECIRC buttons and the "stickman" figure will appear, indicating the Fault Code Mode. Fault codes from 1 to 64 will appear if there are codes in memory. Record these codes and compare them to the chart to find the areas requiring further diagnosis.
7. If Fault Code 25 or 29 appears, the ATC/AZC control module itself must be replaced before any further testing is done. Current fault codes are cleard whenever the problem is solved or goes away. To cleare historical faults, hold the AC or RECIRC button for 3 seconds. The faults have cleared when two horizontal bars appear in the display or they do not appear after several ON/OFF cycles of the ignition key.
8. The ATC/AZC diagnostic system is quite complicated and is capable of displaying data to check both input and output circuitry. Houwver, if you can't find the problem through the basic Fault Code information, take the vehicle to a dealer service department for further testing.

On-board diagnostic chart - 1998 and earlier
Automatic Temperature Control

Current Fault Codes:

Fault Code ------ Description ----------------------Problem Area

00 ........ no faults........................................Norm al Operation
01......... circuit open....................................In-vehicle Temperature Sensor
02......... circuit open....................................Solar Sensor Input Circuit
03......... circuit open....................................Front Panel Blower/Fan Control Input
04......... circuit open....................................Front Panel Mode Control Input
05......... circuit open....................................Blend Air Door Feedback Circuit
06......... circuit open....................................Mode Door Feedback Circuit
07……….. feedback too high...........................Blower/Fan Feedback Circuit
08..........circuit shorted................................In-vehicle Temperature Sensor
09......... circuit shorted................................Solar Sensor Input Circuit
10......... circuit shorted................................Front Panel Blower/Fan Control Input
11......... circuit shorted................................Front Panel Mode Control Input
12......... circuit shorted............................... Blend Air Door Feedback Circuit Input
13......... circuit shorted............................... Mode Door Feedback Circuit
14......... feedback too low............................ Blower/Fan Feedback Circuit
15......... door not responding....................... Mode Door Feedback Circuit
16......... door not responding........................Blend Air Door Actuator Drive Circuit
17......... door travel range too small...............Mode Door Feedback Circuit
18......... door travel range too large…............Mode Door Feedback Circuit
19......... door travel range too small..............Blend Air Door Actuator Drive Circuit
20......... door travel range too large..............Blend Air Door Actuator Drive Circuit
21......... calibration data error......................Calibration and CPU Data
22......... BCM message missing……………..….....Collision Detection C2D BUS Inputs
23......... PCM message missing.....................Collision Detection C2D BUS Inputs
24......... CPU error......................................Calibra tion and CPU Data
25……….reserved
26………….reserved
27………….reserved

Historical Fault Codes:

28………….circuit was open……………………………….in-vehicle temperature sensor
29………….circuit was open……………………………….Solar Sensor Input Circuit
30………….circuit was open……………………………….Front Panel Blower/Fan Control Input
31………….circuit was open……………………………….Front Panel Mode Control Input
32......... circuit was open.............................Blend Air Door Feedback Circuit
33......... circuit was open.............................Mode Door Feedback Circuit
34......... feedback was too high....................Blower/Fan Feedback Circuit
35......... circuit was shorted.........................In-vehicle Temperature Sensor
36......... circuit was shorted.........................Solar Sensor Input Circuit
37......... circuit was shorted..........................Front Panel Blower/Fan Control Input
38......... circuit was shorted..........................Front Panel Mode Control Input
39......... circuit was shorted..........................Blend Air Door Feedback Circuit
40......... circuit was shorted..........................Mode Door Feedback Circuit
41......... feedback was too low......................Blower/Fan Feedback Circuit
42......... door was not responding..................Mode Door Feedback Circuit
43......... door was not responding..................Blend Air Door Actuator Drive Circuit
44......... door range travel was too small…......Mode Door Feedback Circuit
45......... door range travel was too large.........Mode Door Feedback Circuit
46......... door range travel was too small.........Blend Air Door Actuator Drive Circuit
47......... door range travel was too large.........Blend Air Door Actuator Drive Circuit
48......... calibration data was in error.............Calibration and CPU Data
49......... BCM message was missing……………....Collision Detection C2D BUS Inputs
50......... PCM message was missing………………..Collision Detection C2D BUS Inputs
51......... CPU was in error.............................Calibration and CPU Data
52………….reserved
53………….reserved
54………….reserved


1999 and later to follow

[Meerkat]

Automatic Zone Control - 1999 and Later

Fault Codes....................Circuit Description
01...........................IR Thermister circuit open
02...........................IR thermister circuit shorted
03...........................Fan pot shorted
04...........................Fan pot open
05...........................Mode pot shorted
06...........................Mode pot open
07...........................IR sensor delta too large
08...........................Reserved
09...........................Reserved
10...........................Reserved
11...........................Engine air intake temperature Buss message missing
12...........................Country code Buss message missing
13...........................Mode motor not responding
14...........................AI (Recirc) motor not responding
15...........................Left temperature door not responding
16...........................Right temperature door not responding
17...........................Mode door travel range too small
18...........................Mode door travel range too large
19...........................AI (Recirc) door travel too small
20...........................AI (Recirc) door travel too large
21...........................Left temperature door travel too small
22...........................Left temperature door travel too large
23...........................Right temperature door travel too small
24...........................Right temperature door travel too large
25...........................Calibration check sum error
26...........................Engine coolant temp bus message missing
27...........................Vehicle speed bus message missing
28...........................Engine RPM bus message missing
29...........................OAT bus message missing
30...........................Display intensity bus message missing
31...........................VIN number bus message missing
32...........................Reserved
33...........................IR Thermister circuit was open
34...........................IR thermister circuit was shorted
35...........................Fan pot was shorted
36...........................Fan pot was open
37...........................Mode pot was shorted
38...........................Mode pot was open
39...........................IR sensor delta was too large
40...........................Reserved
41...........................Reserved
42...........................Reserved
43...........................Engine air intake temperature Buss message missing
44...........................Country code Buss message missing
45...........................Mode motor was not responding
46...........................AI (Recirc) motor was not responding
47...........................Left temperature door was not responding
48...........................Right temperature door was not responding
49...........................Mode door travel range too small
50...........................Mode door travel range too large
51...........................AI (Recirc) door travel too small
52...........................AI (Recirc) door travel too large
53...........................Left temperature door travel too small
54...........................Left temperature door travel too large
55...........................Right temperature door travel too small
56...........................Right temperature door travel too large
57...........................Calibration check sum error
58...........................Engine coolant temp bus message missing
59...........................Vehicle speed bus message missing
60...........................Engine RPM bus message missing
61...........................OAT bus message missing
62...........................Display intensity bus message missing
63...........................VIN number bus message missing