Grand Cherokee 4WD V8-4.7L (2003)
SIDE IMPACT SENSOR
The side impact sensors are electronic accelerometers that sense the rate of vehicle deceleration and when combined with the ACM Accelerometer
provides verification of the direction and severity of a side impact. Each sensor also contains an electronic communication chip that allows the unit to
communicate the sensor status as well as sensor fault information to the microprocessor in the Airbag Control Module. The ACM microprocessor
continuously monitors all of the passive restraint system electrical circuits to determine the system readiness. If the ACM detects a system fault, it sets
a Diagnostic Trouble Code and controls the airbag warning indicator operation accordingly. The side impact sensors receive battery current and
ground through dedicated driver and passenger sensor signal and ground circuits from the ACM. The impact sensors and the ACM communicate by
modulating the voltage in the sensor signal circuit. If the sensor is dropped it must be replaced. Disconnect the battery or remove both airbag fuses
before servicing impact sensors.
CAUTION: Do not remove or install the impact sensors while the sensor is connected to the vehicle wiring.
SPECIAL TOOLS
Some airbag diagnostic test use special tools, airbag load tools, 8310 and 8443 for testing squib circuits. The load tools contain fixed resistive loads,
jumpers and adapters. The fixed loads are connected to cables and mounted in a storage case. The cables can be directly connected to some airbag
system connectors. Jumpers are used to convert the load tool cable connectors to the other airbag system connectors. The adapters are connected to the
module harness connector to open shorting clips and protect the connector terminal during testing. When using the load tool follow all of the safety
procedures in the service information for disconnecting airbag system components. Inspect the wiring, connector and terminals for damage or
misalignment. Substitute the airbag load tool in place of a Driver or Passenger Airbag, curtain airbag, clockspring (use a jumper if needed). Then
follow all of the safety procedures in the service information for connecting airbag system components. Read the module active DTC's. If the module
reports NO ACTIVE DTC's the defective components has been removed from the system and should be replaced. If the DTC is still active, continue
this process until all component in the circuit have been tested. Then disconnect the module connector and connect the matching adapter to the module
connector. With all airbags disconnected and the adapter installed the squib wiring can be tested for open and shorted conditions.
DIAGNOSTIC TROUBLE CODES
Airbag diagnostic trouble codes consist of active and stored codes. If more than one code exists, diagnostic priority should be given to the active
codes. Each diagnostic trouble code is diagnosed by following a specific testing procedure. The diagnostic test procedures contain step-by-step
instructions for determining the cause of the trouble codes. It is not necessary to perform all of the tests in this book to diagnose an individual code.
Always begin by reading the diagnostic trouble codes with the DRBIII. This will direct you to the specific test(s) that must be performed. In certain
test procedures, diagnostic trouble codes are used as a diagnostic tool.
Active Codes
The code becomes active as soon as the malfunction is detected or key-on, whichever occurs first. An active trouble code indicates an on-going
malfunction. This means that the defect is currently there every time the airbag control module checks that circuit or component. It is impossible to
erase an active code. Active diagnostic trouble codes for the airbag system are not permanent and will change within 12 seconds the reason for the
code is corrected. With the exception of the warning lamp trouble codes or malfunctions, when a malfunction is detected, the airbag lamp remains lit
for a minimum of 12 seconds or as long as the malfunction is present.
Stored Codes
Airbag codes are automatically stored in the ACM's memory as soon as the malfunction is detected. A stored code indicates there was an active code
present at some time. When a trouble code occurs, the airbag warning indicator illuminates for 12 seconds minimum (even if the problem existed for
less than 12 seconds). The code is stored, along with the time in minutes it was active, and the number of times the ignition has been cycled since the
problem was last detected.
The minimum time shown for any code Will be one minute, even if the code was actually present for less than one minute. Thus, the time shown for a
code that was present for two minutes 13 seconds, for example, would be three minutes. If a malfunction is detected a diagnostic trouble code is
stored and will remain stored. When and if the malfunction ceases to exist, an ignition cycle count will be initiated for that code. If the ignition cycle
count reaches 254 without a reoccurrence of the same malfunction, the diagnostic trouble code is erased and that ignition cycle counter is reset to zero.
If the malfunction reoccurs before the count reaches 254, then the ignition cycle counter will be reset and diagnostic trouble code will continue to be a
stored code. If a malfunction is not active while performing a diagnostic test procedure, the active code diagnostic test will not locate the source of the
problem. In this case, the stored code can indicate an area to inspect. Maintain a safe distance from all airbags while performing the following
inspection. If no obvious problems are found, erase stored codes, and with the ignition on wiggle the wire harness and connectors, rotate the steering
wheel from stop to stop. Recheck for codes periodically as you work through the system. This procedure may uncover a malfunction that is difficult to
locate.
Audio System
AUDIO SYSTEM
The PCI Bus inputs into the radio are used for VF dimming and remote steering wheel controls. All the radios are capable of displaying faults and
allowing certain actuation tests through the use of the DRBIII. When attempting to perform PCI Bus diagnostics, the first step is to identify the radio
in use in the vehicle.
When trouble shooting output shorts or "output" error messages, the following applies:
On radios without an external amplifier, the term output refers to the path between the radio and the speaker. This type of circuit can be monitored all
the way through the speaker connections by the radio assembly. When the radio displays a shorted output DTC with this type of system, the speaker,
