Silverado 1500 2WD V8-4.8L VIN V (2006)
Auxiliary Power Outlet: Symptom Related Diagnostic Procedures
120-VOLT POWER RECEPTACLE(S) INOPERATIVE
DIAGNOSTIC FAULT INFORMATION
IMPORTANT:
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This diagnostic procedure is only for an APO that is inoperative or with a Driver Information Center (DIC) message, and with no DTC's set
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Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. See: Powertrain Management/Computers and
Control Systems/Testing and Inspection/Diagnostic Trouble Code Tests and Associated Procedures
CIRCUIT/SYSTEM DESCRIPTION
The auxiliary power outlet (APO) switch controls the operation of the hybrid control module (HCM) APO state manager. The APO state manager
commands one of 3 states from the starter generator control module (SGCM), (APO Off, APO Normal, APO Continuous). The APO switch is a
momentary button, its output signal an input to an HCM analogue channel. Five volts are supplied to the switch, the returned voltage is measured
relative to HCM signal ground to determine the switch state. A resistor network in the switch circuitry ensures that shorted high and low states can be
diagnosed successfully. There are 2 valid voltage ranges of the return signal, one representing switch open, the other representing switch closed. If the
voltage is lower than a threshold, a short low is indicated. Similarly, if the voltage is greater than the short high threshold, a short 'high' is indicated.
The SGCM uses the interlock circuit to monitor the plugs and connectors for hybrid system function. The interlock indicates the state of the
connectors in the 120 voltage circuits. In the SGCM, the primary side of the transformer is connected to a low frequency oscillator circuit. When the
loop is complete, the shorted secondary reduces the oscillator voltage, and a comparator senses this as a good and complete interlock loop. If the loop
is open, the oscillator amplitude increases and the comparator senses this as a problem. Short Circuits, Overloads and Ground Fault Detection (GFD)
Short Circuits, Overloads and Ground Fault Detection (GFD)
The SGCM monitors ground faults and overloads as well as APO system faults and will disable the APO's when these faults occur. The SGCM tests
the ground fault circuit integrity once per ignition cycle and every time the APO is enabled.
The 120-volt AC power outlets are protected against short circuits, overloads and ground faults. If the system detects a short or overloaded circuit, it
will immediately shut down the outlets and the light next to the APO button will flash, while at the same time a 120V OVERLOAD or GROUND
FAULT message will appear in the Driver Information Center (DIC). After the fault condition is corrected, the system can be reset by pressing and
releasing the APO button. See "APO Operating Mode" for more information on the APO button. Short circuits may occur because a defective
extension cord or defective electrical device is plugged into an outlet.
CIRCUIT/SYSTEM TESTING
IMPORTANT: Always perform the Energy Storage Box (ESB) Service Disconnect/Connect (5.3L Engine w/RPO HP2) before diagnosing or
servicing any PHT systems.
1. With the ignition OFF, Isolate the APO circuit that is inoperative by disconnecting the 120-volt harness (orange) from the energy storage box
(ESB) and the SGCM.
2. With a DMM, independently test the APO phase A (hot) and the APO neutral circuits for an open. Also, test the same circuits for a short between
each other.
3. Test the APO ground circuits for any shorts. As the circuits are normally open.
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If a defective circuit is found, repair as necessary.
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If no trouble found with the APO circuits, replace the appropriate APO receptacles.
