Grand Cherokee 2WD Limited V8-4.7L (2002)
2. Turn the ignition switch to the ON position.
3. Continue to hold both buttons until the software versions are displayed, then release the buttons.
4. All of the VFD segments will illuminate for 2-4 seconds. Check for segments that do not illuminate or illuminate all the time.
5. When the self-check is complete the EVIC will display one of the following messages:
-
PASS SELF TEST
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FAILED SELF TEST
-
NOT RECEIVING J1850 MESSAGE
6. To exit the self-check mode, depress the RESET button or cycle the ignition switch and the EVIC will return to normal operation.
If a Communication fault is displayed, refer to the symptom list. If a FAILED is displayed, the EVIC must be replaced.
Ambient Temperature Sensor
The ambient air temperature is monitored by the BCM and displayed by the EVIC. The BCM receives a hardwire input from the Ambient
Temperature Sensor (ATS).
The ATS is a variable resistor that operates on a 5-volt reference signal circuit hardwired from the BCM. The resistance in the ATS changes as the
outside temperature rises or falls. The BCM senses the change in reference voltage through the ATS resistor. Based on the resistance of the ATS,
the BCM is programmed to correspond to a specific temperature. The BCM stores and filters the ambient temperature data and transmits this data
to the EVIC via the PCI Bus. The ATS cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.
Ambient Temperature Sensor Fault Codes
The outside temperature function is supported by the ambient temperature sensor (ATS), a signal and ground circuit hardwired to the BCM, and
the EVIC display.
If the EVIC display indicates 54 °C (130 °F) or the ATS sense circuit is shorted to ground, the temp display will be 54 °C (130 °F) to indicate a
SHORT circuit condition.
If the EVIC display indicates -40 °C (-40 °F) or the ATS sense circuit is open, the temp display will be -40 °C (-40 °F) to indicate an OPEN
circuit condition.
If there is an OPEN or SHORT circuit condition, it must be repaired before the EVIC VFD can be tested.
The ATS is supported by the BCM. Ambient Temperature Sensor DTCs will be recorded in the BCM. The ATS can be diagnosed using the
following Sensor Test. Test the ATS circuits using the diagnostics in the Body Diagnostic Procedures Manual. If the EVIC passes the self test, and
the ATS, the circuits, and PCI bus communications are confirmed to be OK, but the EVIC temperature display is inoperative or incorrect, replace
the BCM.
Ambient Temperature Sensor Test
1. Turn the ignition OFF.
2. Disconnect the ATS harness connector.
3. Measure the resistance of the ATS using the following min/max values:
TEMPERATURE ........................................................................................................................................................................... RESISTANCE
0 °C (32 °F) ....................................................................................................................................................................... 29.33 - 35.99 Kilohms
10 °C (50 °F) ..................................................................................................................................................................... 17.99 - 21.81 Kilohms
20 °C (68 °F) ..................................................................................................................................................................... 11.37 - 13.61 Kilohms
25 °C (77 °F) ....................................................................................................................................................................... 9.12 - 10.86 Kilohms
30 °C (86 °F) ......................................................................................................................................................................... 7.37 - 8.75 Kilohms
40 °C (104 °F) ....................................................................................................................................................................... 4.90 - 5.75 Kilohms
The sensor resistance should read between these min/max values. If the resistance values are not OK, replace the sensor.
HomeLink Universal Transmitter
If equipped, the HomeLink Universal Transmitter is integrated into the overhead console. For added security it will operate home security systems
that use coded signals known generically as Rolling Codes. The overhead console display provides visual feedback to the driver, indicating which
HomeLink transmitter channel button is being pressed. The HomeLink can learn and store up to three separate transmitter radio frequency codes to
operate garage door openers, security gates, and security lighting. The HomeLink buttons are marked with one, two, or three dots. For complete
information, refer to Universal Transmitter in the Owner's Manual.
TIRE PRESSURE MONITORING SYSTEM (TPM)
If equipped with the Tire Pressure Monitoring System (TPM), each of the vehicles five wheels will have a valve stem with an integral pressure
sensor and radio transmitter. Radio signals from the tire pressure sensor/transmitters are received and interpreted by the Electronic Vehicle
Information Center (EVIC).
A sensor/transmitter in a mounted wheel will broadcast its detected pressure once per minute when the vehicle speed is greater than 40 km/h (25