VUE AWD V6-3.5L VIN 4 (2004)
PCM Long Term Memory and Engine Off Diagnostics
Several ignition positive voltage circuits supply battery power to the PCM even when the ignition switch is turned OFF. The continuous battery power
enables the PCM to support a long term memory. The long term memory provides storage of diagnostic trouble codes, diagnostic test status, and the
aforementioned "learned values" that improve driveability.
Another use of continuous battery power is the PCM can run certain system diagnostics with the engine off. One of these diagnostics is the engine off
natural vacuum (EONV) EVAP system leak test. With the engine OFF, the PCM can turn on the main relay and provide power to operate the EVAP
solenoids while monitoring the fuel tank pressure. During the running of the EONV diagnostic routine, the PCM can be fully powered up for as long
as 30 minutes.
PCM Output Controls
The powertrain control module (PCM) can be directed by a scan tool to operate certain solenoids, valves, motors, and switches. This scan tool
function is generally referred to as Output Controls. The Output Controls can be found under Special Functions selection of the scan tool. Some
Output Controls may be disabled by the PCM during certain types of vehicle operation. Operating a PCM controlled device with the scan tool should
be limited to a maximum of ten seconds per test period.
Data Link Connector (DLC)
IMPORTANT: Do not use a scan tool that displays faulty data. Report the scan tool problem to the manufacturer. Use of a faulty scan tool can result
in misdiagnosis and unnecessary parts replacement.
The provision for communicating with the control module is the data link connector (DLC). The DLC is located under the instrument panel to the left
of the steering column. The DLC is used to connect to a scan tool.
Some common uses of the scan tool are listed below:
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Identifying stored diagnostic trouble codes (DTCs)
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Clearing the DTCs
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Performing output control tests
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Reading the serial data
Reading Diagnostic Trouble Codes
The procedure for reading diagnostic trouble codes is to use a diagnostic scan tool. Follow the instructions supplied by the scan tool manufacturer in
order to read DTCs accurately.
Clearing Diagnostic Trouble Codes
IMPORTANT: Do not clear the DTCs unless directed to do so by the service information provided for each diagnostic procedure. The Freeze Frame
data which may help diagnose an intermittent fault will be erased from the memory when the DTCs are cleared.
The PCM will begin to count the warm-up cycles when the fault that caused the DTC to be stored into memory has been corrected. The DTC will
automatically be cleared from the PCM memory when the PCM has counted 40 consecutive warm-up cycles with no further faults detected.
Diagnostic trouble codes (DTCs) can be cleared using a scan tool. In order to clear DTCs, use the scan tools Clear DTC Information function. Follow
the instructions supplied by the scan tool manufacturer.
Aftermarket (Add-On) Electrical and Vacuum Equipment
NOTE:
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Connect any add-on electrically operated equipment to the vehicle's electrical system at the battery (power and ground) in order to prevent damage
to the vehicle.
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Do not attach add-on vacuum operated equipment to this vehicle. The use of add-on vacuum equipment may result in damage to vehicle
components or systems.
