Computer/integrating Systems: Diagnosis Chevrolet Uplander I

DIAGNOSTIC CODE INDEX

DIAGNOSTIC CODE INDEX

Begin the system diagnosis with Diagnostic System Check - Vehicle in Vehicle DTC Information. The Diagnostic System Check - Vehicle will provide the following information

1. The identification of the control modules which are not communicating.
2. The identification of any stored diagnostic trouble codes (DTCs) and their status.

The use of the Diagnostic System Check - Vehicle will identify the correct procedures to begin vehicle diagnosis. These must be performed before system DTC or symptom diagnosis.

Scan Tool Output Controls

Scan Tool Output Controls

Scan Tool Data List

Scan Tool Data List

Circuit Description

The internal fault detection is handled inside the control module. No external circuits are involved.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC B1000 Electronic Control Unit (ECU) Performance

Conditions for Running the DTC

The microprocessor runs the program to detect an internal fault when power up is commanded. The only requirements are voltage and ground. This program runs even if the voltage is out of the valid operating range.

Conditions for Setting the DTC

1. The control module detects an internal write malfunction.
2. The control module detects an internal checksum malfunction.

Action Taken When the DTC Sets

The microprocessor refuses all additional inputs.

Conditions for Clearing the DTC

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Diagnostic Aids

1. This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
2. If this DTC is retrieved as both a current and history DTC, replace the module.

DTC B1000

Some control modules must be configured with serial numbers, vehicle options or other information. If a control module was not properly configured after installation, that module may set DTC B1001.

This diagnostic procedure supports the following DTC

DTC B1001 Option Configuration Error

The ignition is ON.

The control module is not configured properly.

1. The SERVICE VEHICLE SOON indicator illuminates.
2. The check gages chime sounds.

1. A current DTC B1001 will clear when the module is correctly programmed.
2. A history DTC B1001 will clear after the ignition has been cycled 100 times, without a repeat of the malfunction.

The most likely reasons for DTC B1001 being set are incorrect calibration files were downloaded to the module or the module was replaced without the recalibration having been performed.

The internal fault detection is handled inside the control module. No external circuits are involved.

This diagnostic procedure supports the following DTC

DTC B1004 Electronic Control Unit Identification Circuit

The module microprocessor must be active/awake.

This DTC indicates the keep alive memory (KAM) in the module has been reset. It is a normal occurrence when battery positive voltage or ground is removed from the module, such as a battery disconnect.

The microprocessor reverts back to the base programmed critical operating data until new data is learned and stored in KAM.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
2. If this DTC is retrieved as both a current and history DTC, replace the module.

DTC B1004

As part of normal data processing, the module performs a data programming check on its writes to the electrically erasable programmable read only memory (EEPROM). The EEPROM write error detection is handled inside the control module. No external circuits are involved.

This diagnostic procedure supports the following DTC

DTC B1007 EEPROM Read/Write Error

The module runs the program to detect an EEPROM write error. The only requirements are battery positive voltage and ground. This program runs even if the battery positive voltage is out of the valid operating range.

The module writes information to a data block in the EEPROM. The module then reads the data and compares it to what was sent to the data block. If the data does not match after 3 consecutive attempts, the module sets the DTC.

The module writes to another area of the EEPROM, this becomes the new permanent area to store the data. The data location is allowed to change until all of the available EEPROM is used. If a DTC B1004 is also set, the module reverts to base operation values programmed for those blocks of data that have failed. The blocks of data that have not failed the checksum test are not affected.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
2. If this DTC is retrieved as both a current and history DTC, replace the module.

DTC B1007

The electrically erasable programmable read-only memory (EEPROM) checksum error detection is handled inside the control module. No external circuits are involved.

This diagnostic procedure supports the following DTC

DTC B1009 EEPROM Checksum Mismatch

The module runs the program to detect an EEPROM checksum error after each wake-up. The only requirements are battery positive voltage and ground. This program runs even if the voltage is out of the valid operating range.

The module retains an inverse copy of the digital value stored in certain blocks of memory in the EEPROM. The module then reads the information from those certain blocks and adds the stored inverse value to the current value. If they do not equal 0, the module sets the DTC.

The module reverts to base operation values programed for those blocks of data that have failed the checksum test. The blocks of data that have not failed the checksum test are not affected.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
2. If this DTC is retrieved as both a current and history DTC, replace the module.

DTC B1009

The electrically erasable programmable read-only memory (EEPROM) checksum error detection is handled inside the control module. No external circuits are involved.

This diagnostic procedure supports the following DTC

DTC B1013 Calibration Read Only Memory (ROM) Checksum Error

The module runs the program to detect an EEPROM checksum error after each wake-up. The only requirements are battery positive voltage and ground. This program runs even if the voltage is out of the valid operating range.

The module retains an inverse copy of the digital value stored in certain blocks of memory in the EEPROM. The module then reads the information from those certain blocks and adds the stored inverse value to the current value. If they do not equal 0, the module sets the DTC.

The module reverts to base operation values programed for those blocks of data that have failed the checksum test. The blocks of data that have not failed the checksum test are not affected.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
2. If this DTC is retrieved as both a current and history DTC, replace the module.

DTC B1013

The body control module (BCM), monitors the ignition inputs OFF, ignition 3, crank and ignition 1 supplied from the ignition switch. The BCM uses the sequence that the signals appear and their voltage levels to determine the power mode called for by the vehicle operator using the ignition switch. A 12-volt reference voltage is supplied by the BCM to the ignition switch over a discrete circuit. The ignition switch uses this voltage for power mode signal discrimination. When the operator places the ignition switch in the Run or Start position, the ignition 1 circuit is delivers the signal to the BCM.

This diagnostic procedure supports the following DTC

DTC B1370 Device Ignition 1 (ON and START) Circuit

1. The BCM must be powered and must detect a change in the ignition switch circuit states.
2. The vehicle battery must be fully charged.

The BCM detects that the ignition 1 signal is shorted to ground, voltage or open for more than 10 seconds in the current ignition cycle.

1. The BCM stores DTC to memory.
2. The BCM operates in a fail-safe power mode dependent on the last valid power mode detected and the state of the engine run flag data on the class 2 serial data communications circuits.
3. The other modules on the vehicle operate in a fail safe power mode dependent on the last valid power mode transmitted by the BCM and the state of the engine run flag on the class 2 serial data communications circuits.

1. A current DTC clears on the next malfunction-free cycle.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

A history DTC maybe caused by an intermittent short or open in the ignition 1 circuit. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

The body control module (BCM) monitors the ignition inputs OFF, ignition 3, crank and ignition 1 supplied from the ignition switch. The BCM uses the sequence that the signals appear and their voltage levels to determine the power mode called for by the vehicle operator using the ignition switch. A 12-volt reference voltage is supplied by the BCM to the ignition switch over a discrete circuit. The ignition switch uses this voltage for power mode signal discrimination. When the operator places the ignition switch in the Run or Accessory position, the ignition 3 circuit delivers the signal to the BCM.

This diagnostic procedure supports the following DTC

DTC B1380 Device Ignition ACCESSORY Circuit

1. The BCM must be powered and must detect a change in the ignition switch circuit states.
2. The vehicles battery must be fully charged.

The BCM detects that the ignition 3 signal is shorted to ground, voltage or open for more than 10 seconds in the current ignition cycle.

1. The BCM stores DTC to memory.
2. The BCM operates in a fail-safe power mode dependent on the last valid power mode detected and the state of the engine run flag data on the class 2 serial data communications circuits.
3. The other modules on the vehicle operate in a fail safe power mode dependent on the last valid power mode transmitted by the BCM and the state of the engine run flag on the class 2 serial data communications circuits.

1. A current DTC clears on the next malfunction-free cycle.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

A history DTC maybe caused by an intermittent short or open in the ignition 3 circuit. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

The body control module (BCM), monitors the ignition inputs OFF, ignition 3, crank and ignition 1 supplied from the ignition switch. The BCM uses the sequence that the signals appear and their voltage levels to determine the power mode called for by the vehicle operator using the ignition switch. A 12-volt reference voltage is supplied by the BCM to the ignition switch over a discrete circuit. The ignition switch uses this voltage for power mode signal discrimination. When the operator places the Ignition switch in the Start position, the Crank circuit delivers the signal to the BCM.

This diagnostic procedure supports the following DTC

DTC B1385 Device Ignition START Circuit

1. The BCM must be powered and must detect a change in the ignition switch circuit states.
2. The vehicles battery must be fully charged.

The BCM detects that the crank signal is shorted to ground, voltage or open for more than 10 seconds in the current ignition cycle.

1. The BCM stores DTC to memory.
2. The engine will not crank.
3. The BCM operates in a fail-safe power mode dependent on the last valid power mode detected and the state of the engine run flag data on the class 2 serial data communications circuits.
4. The other modules on the vehicle operate in a fail safe power mode dependent on the last valid power mode transmitted by the BCM and the state of the engine run flag on the class 2 serial data communications circuits.

1. A current DTC clears on the next malfunction-free cycle.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

A history DTC maybe caused by an intermittent short or open in the crank circuit. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

The body control module (BCM) has an internal battery voltage sensor and a reference voltage. The BCM compares these 2 voltages via the 2 battery positive voltage circuits every 300 milliseconds.

This diagnostic procedure supports the following DTC

DTC B1390 Device Voltage Reference Input Circuit

This DTC will run only if the BCM has power and ground. This DTC will execute regardless of the source voltage.

This code shall be set after 10 consecutive readings that the 2 battery positive voltages differ by one volt or greater.

All writes to the electrically erasable programmable read only memory (EEPROM) will be suspended. All loss of communication and low/high voltage DTC codes are suspended.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

DTC B1390

The body control module (BCM) monitors the battery voltage through the battery positive voltage circuit. If the BCM senses that battery voltage is outside of its normal range for 1 second, DTC B1420 will set.

This diagnostic procedure supports the following DTC

DTC B1420 Device Voltage

The voltage supplied to the BCM is in the range of 7-26 volts.

The voltage supplied to the body control module is in the range of 7-26 volts.

1. The BCM senses a battery voltage above or below the specified range of 9-16 volts.
2. The above condition lasts for at least 1 second.

1. The BCM will disable all its outputs when a high voltage condition is detected.
2. The setting of this DTC inhibits the setting of other DTCs.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the ignition has been cycled 100 times, without a repeat of the malfunction.

1. The following may cause an intermittent: A damaged terminal A backed out terminal A poor terminal tension A chafed wire A broken wire inside the insulation
2. When diagnosing an intermittent short or an open, manipulate the wire harness while watching the test equipment for changes.

DTC B1420

The body control module (BCM) controls the Ignition 1 (IGN 1) relay. The contacts of the IGN 1 relay deliver a B+ signal to the following components

1. The antilock brake system (ABS) functions
2. The AC compressor relay
3. The crank relay
4. The HVAC control head
5. The instrument panel cluster (IPC)
6. The powertrain control module (PCM)
7. The sensing and diagnostic module (SDM)
8. The transmission solenoids

The BCM will energize the IGN 1 relay when the vehicle is in the RUN or CRANK power mode. The BCM supplies a B+ signal to the relays control circuit to energize it. The relays control circuit receives it's ground from G113. If a short or circuit malfunction takes place in the IGN 1 control circuit the BCM will set a B1428 and the relay will not energize.

This diagnostic procedure supports the following DTC

DTC B1428 Ignition-Switched Power Relay Circuit

The ignition switch is in the RUN or CRANK position.

1. A DTC B1428 sets when the BCM detects a short to ground in the IGN 1 relay control feed circuit when it is trying to energize the IGN 1 relay.
2. A DTC B1428 sets when the BCM detects an open in the IGN 1 relay control feed circuit when it is trying to energize the IGN 1 relay.
3. The conditions above must be present for more than 0.3 second.

The BCM stores DTC B1428 in memory.

1. A short to ground or a malfunction in the IGN 1 relay control feed circuit is no longer detected by the BCM.
2. A history DTC B1428 will clear after the modules ignition counter reaches the reset threshold, without a repeat of the malfunction.

1. If the DTC B1428 is a history DTC, the fault may be intermittent. Refer to «Testing for Intermittent Conditions and Poor Connections»(ref-241671-S27410119602006081100000) .
2. The following conditions may cause an intermittent malfunction to occur: An intermittent short to ground in the IGN 1 relay control feed circuit The IGN 1 relay coil is shorted to ground internally The BCM is shorted to ground internally

The body control module (BCM) controls the HVAC blower motors through the RUN relay circuit. When the ignition switch is in either the ACC or the ON position, the BCM provides battery negative voltage to the RUN relay control circuit. When the RUN relay is energized, it supplies B+ to the HVAC blower motor switches.

This diagnostic procedure supports the following DTC

DTC B1433 Ignition-Switched Power Relay 2 Circuit

The system voltage must be between 9-16 volts.

1. The BCM detects a short to voltage in the RUN relay control circuit when the BCM is trying to energize the relay.
2. The BCM detects that the RUN relay control circuit is open.
3. The condition above must be present for more than 1 second.

1. The BCM stores DTC B1433 in memory.
2. The devices powered by the RUN supply voltage circuit will not operate.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

The body control module (BCM) controls various accessories through the retained accessory power (RAP) relay circuit. When the ignition switch is in either the ACC or the ON position, the BCM provides battery negative voltage to the RAP relay control circuit. When the RAP relay is energized, it supplies a B+ to the accessories not controlled by a serial data power mode message.

When the ignition switch turns from ON or ACC to OFF, with all of the vehicle doors closed, the BCM keeps the relay energized for 10 minutes or until any vehicle door opens.

This diagnostic procedure supports the following DTC

DTC B1475 Retained Accessory Power Circuit

The system voltage must be between 9-16 volts.

1. The BCM detects a short to voltage in the RAP relay control circuit when the BCM is trying to energize the relay.
2. The BCM detects that the RAP relay control circuit is open.
3. The condition above must be present for more than 1 second.

1. The BCM stores DTC B1475 in memory.
2. The devices powered by the RAP supply voltage circuit will not operate.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

The internal fault detection is handled inside the control module. No external circuits are involved.

This diagnostic procedure supports the following DTC

DTC C0550 Electronic Control Unit (ECU) Performance

The microprocessor runs the program to detect an internal fault when power up is commanded. The only requirements are voltage and ground. This program runs even if the voltage is out of the valid operating range.

1. The control module detects an internal write malfunction.
2. The control module detects an internal checksum malfunction.

If equipped, the following module specific actions may occur

1. The ABS indicator turns on.
2. The BRAKE Warning indicator turns on.
3. The SERVICE 4WD indicator turns on and the system will be disabled.
4. The Service 4 Wheel Steering indicator turns on and the system will be disabled.
5. The SERVICE RIDE SYS or SERVICE RIDE CONTROL message is displayed.
6. The SERVICE SUSPENSION SYS message is displayed.
7. The traction control system (TCS) indicator turns ON.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
2. If this DTC is retrieved as both a current and history DTC, replace the module.

DTC C0550

The ignition 1 relay is controlled by the body control module (BCM). The ignition 1 relay contacts are supplied a hot at all times from the fuse block underhood. The relay supplies power to several components when the vehicle is in the RUN or CRANK power mode. When the ignition switch is placed in the RUN or CRANK position, the BCM will receive an ignition 1 signal from the ignition switch and turn ON the ignition 1 relay. When the ignition switch is in the OFF position, the BCM will turn OFF the ignition 1 relay. The powertrain control module (PCM) compares the ignition 1 relay output signal with the BCM class 2 serial data power mode message, if the ignition 1 voltage signal and the power mode message do not match for an allotted time, the PCM will disable the fuel injectors and DTC P2535 will set.

This diagnostic procedure supports the following DTC

DTC P2535 Ignition One Voltage High

1. The vehicle is in PARK or NEUTRAL.
2. The ignition switch is OFF.

The ignition 1 voltage signal is higher than normal for more than 7 seconds.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. The driver information center, if equipped, may display a message.

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

DTC P2535

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module receives a message for a critical operating parameter, the module records the identification number of the module which sent the message for state of health (SOH) monitoring. A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. When a module does not associate an identification number with at least one critical parameter within about 5 seconds of beginning serial data communication, DTC U1000 or U1255 is set. If more than one critical parameter does not have an identification number association, the DTC will only be reported once.

DTC Descriptors

This diagnostic procedure supports the following DTCs

1. DTC U1000 Class 2 Data Link Malfunction
2. DTC U1255 Lost Communications

1. Voltage supplied to the module is in the normal operating voltage range of 9-16 volts.
2. Diagnostic trouble codes U1300, U1301 and U1305 do not have a current status.
3. The module operation or the vehicle power mode requires serial data communication to occur.

At least one critical operating parameter has not been associated with an identification number within about 5 seconds after beginning serial data communication.

The module uses a default value for the missing parameter.

1. A current DTC U1000 will clear when all critical operating parameters for the module have been associated with an identification number or at the end of the current ignition cycle.
2. A history DTC U1000 will clear after 50 ignition switch ON/OFF cycles with no repeat of the failure.

When a malfunction, such as an open fuse to a module occurs while modules are communicating, a Lost Communication DTC for a specific module is set as a current DTC. When the modules stop communicating, the current Lost Communication DTC is cleared, but the history DTC remains. When the modules begin to communicate again, the module with the open fuse will not be learned by the other modules, so DTC U1000 is set current by the other modules. If the malfunction occurs when the modules are not communicating, only DTC U1000 or U1255 is set.

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module receives a message for a critical operating parameter, the module records the identification number of the module which sent the message for State of Health monitoring (Node Alive messages). A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. Once an identification number is learned by a module, it will monitor for that modules "Node Alive" message. Each module on the class 2 serial data circuit which is powered and performing functions that require detection of a communications malfunction is required to send a "Node Alive" message every 2 seconds. When no message is detected from a learned identification number for 5 seconds, a DTC U1xxx, where xxx is equal to the 3-digit identification number, is set.

The Control Module ID Number list provides a method for determining which module is not communicating. A module with an internal class 2 serial data circuit malfunction or which loses power during the current ignition cycle would have a Lost Communication DTC set by other modules. The modules that can communicate will set a DTC indicating the module that cannot communicate. When no message is detected from a learned identification number for 5 seconds, a DTC U1xxx, where xxx is equal to the 3-digit identification number, is set.

This diagnostic procedure supports the following DTC

DTC U1XXX Lost communication With XXX Module

DTC U1001-U1254

When more than one Loss of Communication DTC is set in either one module or in several modules, diagnose the DTCs in the following order

1. Current DTCs before history DTCs unless told otherwise in the diagnostic tables.
2. The DTC which is reported the most times.
3. From the lowest number DTC to the highest number DTC.

1. Voltage supplied to the module is in the normal operating voltage range of 9-16 volts.
2. Diagnostic trouble codes U1300, U1301 and U1305 do not have a current status.
3. The vehicle power mode, ignition switch position, requires serial data communication to occur.

A message from a learned identification number has not been detected for the past 5 seconds.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. In addition to this, Node Alive messages are transmitted by each module on the class 2 serial data circuit about once every 2 seconds. When the module detects one of the following conditions on the class 2 serial data circuit for approximately 3 seconds, the setting of all other class 2 serial communication DTCs is inhibited and a DTC will set.

DTC U1300, U1301 or U1305

This diagnostic procedure supports the following DTCs

1. DTC U1300 Class 2 Data Link Low
2. DTC U1301 Class 2 Data Link High
3. DTC U1305 Class 2 Data Link Low or High

Conditions for Running the DTCs

1. Voltage supplied to the module is in the normal operating voltage range.
2. The vehicle power mode requires serial data communication to occur.

The module uses default values for all parameters received on the class 2 serial data circuit.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. These DTCs cannot be retrieved with a current status. Diagnosis of current DTCs is accomplished via the symptom, Scan Tool Does Not Communicate with a Class 2 Device. Refer to «Scan Tool Does Not Communicate with Class 2 Device»(ref-241672-S16124518102006081100000) .
2. An intermittent condition is likely to be caused by a short on the class 2 serial data circuit. Use the Scan Tool Does Not Communicate with a Class 2 Device procedure in order to isolate an intermittent condition. Refer to «Scan Tool Does Not Communicate with Class 2 Device»(ref-241672-S16124518102006081100000) .

1. Perform the «Diagnostic System Check - Vehicle»(ref-241670-S16610990062006081100000) in Vehicle DTC Information before using the symptom tables in order to verify that all of the following are true: There are no DTCs set. The control modules can communicate via the serial data links.
2. Review the system operation in order to familiarize yourself with the system functions. Refer to: «Data Link Communications Description and Operation»(ref-241672-S37251796142006081100000) «Body Control System Description and Operation»(ref-241672-S27295983742006081100000) «Retained Accessory Power (RAP) Description and Operation»(ref-241672-S19729951882006081100000)

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the systems. Refer to «Checking Aftermarket Accessories»(ref-241671-S33907418562006081100000) in Wiring Systems.
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «Scan Tool Does Not Power Up»(ref-241672-S05518575312006081100000)
2. «Scan Tool Does Not Communicate with Class 2 Device»(ref-241672-S16124518102006081100000)

The data link connector (DLC) is a standardized 16 cavity connector. Connector design and location is dictated by an industry wide standard and is required to provide the following

1. Scan tool power battery positive voltage at terminal 16
2. Scan tool power ground at terminal 4
3. Common signal ground at terminal 5

The scan tool will power up with the ignition OFF. Some modules, however, will not communicate unless the ignition is ON and the power mode master (PMM) module sends the appropriate power mode message.

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. Connecting a scan tool to the data link connector (DLC) allows communication with the modules for diagnostic purposes. DTCs may be set due to this symptom and during this diagnostic procedure. Complete the diagnostic procedure in order to ensure all the DTCs are diagnosed and cleared from memory.

1. The body control module (BCM) detects that the ignition is ON and sends the appropriate power mode message to the other modules. Therefore, the BCM must be connected to the DLC for any other module to communicate with the scan tool.
2. When the class 2 serial data circuit is shorted to ground or to voltage, the following DTCs may set: U1300 U1301 U1305

Normal vehicle serial data communications and module operations will not begin until the system power mode has been identified. Discrete wires from the ignition switch contacts are monitored by a module which acts as the power mode master (PMM) in order to determine the correct power mode. The module which is the PMM communicates the system power mode to all modules on the serial data lines. Refer to Body Control System Description and Operation to identify which module is the PMM and the applicable power mode look up table.

This table is used for all retained accessory power (RAP) relay and RAP serial data controlled accessories which remain active after RAP has timed out. The RAP relay system can malfunction separately from the serial data controlled RAP system and the serial data controlled RAP system can malfunction separately from the RAP relay. If multiple accessories are not exhibiting an "On After Time-out" symptom, either on the RAP relay controlled circuit or the serial data controlled circuit or both, the malfunction is in a particular device and not in the RAP control system. Refer to Control Module References to locate information on a specific system.

Retained Accessory Power (RAP) On After Timeout