Retained Accessory Power (RAP) Schematics
For retained accessory power schematics refer to appropriate System Wiring Diagrams article.
Diagnostic Starting Point - Retained Accessory Power
Review the Retained Accessory Power (RAP) Description and Operation before you begin the system diagnosis. Reviewing the Description and Operation information will help you determine if the condition described by the customer is normal operation.
Begin the system diagnosis with the Diagnostic System Check - Retained Accessory Power . The Diagnostic System Check will provide the following information
- The identification of the control modules which command the system
- The ability of the control modules to communicate through the serial data circuit
- The identification of any stored diagnostic trouble codes (DTCs) and their status
The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and where the procedure is located.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
- 1: This step verifies that the retained accessory power (RAP) power mode is malfunctioning by checking functions enabled by the body control module (BCM).
- 3: The BCM sends class 2 messages to other control modules via the serial data link, allowing them to operate in RAP power mode. Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
- 5: This step checks for diagnostic trouble codes (DTCs) in the BCM.
- 6: The presence of DTCs which begin with "U" indicate that a control module is not communicating. Diagnose DTCs that begin with "U" before you diagnose any other DTCs.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Retained Accessory Power (RAP) Schematics | |||
| 1 | Turn the ignition to the ON position. Close all of the vehicle doors. Turn the ignition to the OFF position. Operate the driver and passenger power window switches, if equipped. Does the RAP function normally for either power window with either switch? | Go to Diagnostic System Check - Door Systems in Doors | Go to Step 2 |
| 2 | Install a scan tool. Does the scan tool power up? | Go to Step 3 | Go to Scan Tool Does Not Power Up in Data Link Communications |
| 3 | Turn the ignition ON, with the engine OFF. Attempt to communicate with the BCM, using the scan tool. Does the scan tool communicate with the BCM? | Go to Step 4 | Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications |
| 4 | IMPORTANT: The engine may start during the following step. Turn the engine OFF as soon as you have observed the Crank power mode. Access the Class 2 Power Mode in the Diagnostic Circuit Check on the scan tool. Rotate the ignition switch through all positions while observing the ignition switch power mode parameter. Refer to the Serial Data Power Mode table within the Body Control System Description and Operation in Body Control Systems, Body Control System Description and Operation for a list of the power mode states that correspond to each ignition switch position. Does the scan tool display match the ignition switch position for all switch positions? | Go to Step 5 | Go to Power Mode Mismatch in Body Control System |
| 5 | Select the body control module display DTCs function on the scan tool. Does the scan tool display any DTCs? | Go to Step 6 | Go to Symptoms - Retained Accessory Power |
| 6 | Does the scan tool display any DTCs which begin with a "U"? | Go to Diagnostic Trouble Code (DTC) List in Data Link Communications | Go to Step 7 |
| 7 | Does the scan tool display DTCs B1000, B1420, or B1440? | Go to Diagnostic Trouble Code (DTC) List in Body Control System | Go to Step 8 |
| 8 | Does the scan tool display DTC B1480? | Go to DTC B1480 in Lighting Systems | Go to Step 9 |
| 9 | Does the scan tool display DTCs B1477 or B1478? | Go to DTC B1477 or B1478 | Go to Symptoms - Retained Accessory Power |
| IMPORTANT |
|---|
| The engine may start during the following step. Turn the engine OFF as soon as you have observed the Crank power mode. |
Diagnostic System Check - Retained Accessory Power
Scan Tool Output Controls
| Scan Tool Output Control | Additional Menu Selection(s) | Description |
|---|---|---|
| Retained Accessory Power | Miscellaneous Test | Commands the RAP function ON or OFF |
Scan Tool Output Controls
Scan Tool Data List
| Scan Tool Parameter | Data List | Units Displayed | Typical Data Value |
|---|---|---|---|
| Operating Conditions: BCM powered and communicating with the scan tool. | |||
| Accessory Switch | Inputs | On, Off | Off |
| Battery Voltage | Data | Volts | 12.60 |
| Cargo Door Ajar Switch | Inputs | On, Off | Off |
| Driver Door Ajar Sw. | Inputs | On, Off | Off |
| Passenger Door Ajar Sw. | Inputs | On, Off | Off |
| RAP Relay | Outputs | Active, Inactive | Active |
| Run/Crank | Inputs | On, Off | Off |
Scan Tool Data List
Diagnostic Trouble Code (DTC) List
| DTC | Diagnostic Procedure | Module |
|---|---|---|
| B1477 | DTC B1477 or B1478 | BCM |
| B1478 | DTC B1477 or B1478 | BCM |
Diagnostic Trouble Code (DTC) List
Circuit Description
The body control module (BCM) interfaces with the vehicles power distribution system through the WND RAP relay. The WND RAP relay allows the BCM to control the application of power to the feed circuits of the power windows. When the ignition switch is in either the ACC or the ON position, the BCM energizes the WND RAP relay by providing B+ to the WND RAP relay control circuit.
The BCM turns off the WND RAP relay when the ignition switch is in the START position. The RAP feature therefore disables during engine cranking.
When the ignition switch turns from ON or ACC to OFF, with all of the vehicle doors closed, the BCM leaves the WND RAP relay energized for 10 minutes, or until any vehicle door opens.
DTC Descriptors
This diagnostic procedure supports the following DTCs.
- DTC B1477 Retained Accessory Power Circuit Low
- DTC B1478 Retained Accessory Power Circuit High
Conditions for Running the DTC
The system voltage must be between 9-16 volts.
Conditions for Setting the DTC
- DTC B1477: The BCM detects a short to ground in the WND RAP relay control circuit when the BCM is trying to energize the WND RAP relay. The condition above must be present for more than 1 second.
- DTC B1478: The BCM detects a short to battery or an open in the WND RAP relay control circuit when the WND RAP relay is not energized. The condition above must be present for more than 1 second.
Action Taken When the DTC Sets
- DTC B1477: The BCM stores DTC B1477 in memory. The circuits powered by the WND RAP relay will not operate.
- DTC B1478: The BCM stores DTC B1478 in memory. The circuits powered by the WND RAP relay remain powered at all times if the relay control circuit is shorted to battery. The circuits powered by the WND RAP relay will never be powered if the relay control circuit is open.
Conditions for Clearing the DTC
- A current DTC clears when the malfunction is no longer present.
- A history DTC clears when the ignition has been cycled 100 times, without a repeat of the malfunction.
Diagnostic Aids
If the DTC B1477 or B1478 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
The following conditions may cause an intermittent malfunction to occur
- An intermittent short to ground or to battery in the WND RAP relay control circuit.
- The WND RAP relay coil is shorted to ground or to battery internally.
- The BCM is shorted to ground or to battery internally.
The numbers below refer to the step numbers on the diagnostic table.
- 2: During the WND RAP relay operation, listen for an audible click. Command the ON and the OFF states. Repeat the commands as necessary.
- 3: Verifies whether the WND RAP relay has a defect.
- 4: Tests the control circuit of the WND RAP relay.
- 5: Tests the ground circuit of the WND RAP relay.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Retained Accessory Power (RAP) Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems | |||
| 1 | Did you perform the Retained Accessory Power (RAP) Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - Retained Accessory Power |
| 2 | Install a scan tool. Turn ON the ignition, with the engine OFF. Command the RAP relay ON and OFF, with a scan tool. Does the WND RAP relay turn ON and OFF with each command? | Go to Diagnostic Aids | Go to Step 3 |
| 3 | Turn OFF the ignition. Disconnect the WND RAP relay. Connect a test lamp between the relay coil circuits of the WND RAP relay. Command the RAP relay ON and OFF, with a scan tool. Does the test lamp turn ON and OFF with each command? | Go to Step 6 | Go to Step 4 |
| 4 | Test the control circuit between the BCM and the WND RAP relay for a short to voltage, ground or an open. Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 5 |
| 5 | Test the ground circuit of the WND RAP relay coil for a short to voltage or an open. Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 7 |
| 6 | Inspect for poor connections at the WND RAP relay. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 8 |
| 7 | Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 9 |
| 8 | Replace the WND RAP relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems. Did you complete the replacement? | Go to Step 10 | |
| 9 | IMPORTANT: Perform the module setup procedure, if required. Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Perform the setup procedure for the BCM. Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control System. Did you complete the replacement? | Go to Step 10 | |
| 10 | Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC. Does the DTC reset? | Go to Step 2 | System OK |
| IMPORTANT |
|---|
| Perform the module setup procedure, if required. |
DTC B1477 or B1478
Important Preliminary Checks Before Starting
- Perform the «Diagnostic System Check - Retained Accessory Power»(/chevrolet/chevy-express-g3500/1996-2012/remont/accessories-control-systems/#retained-accessory-power-system) 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 link.
- Review the system operation in order to familiarize yourself with the system functions. Refer to «Retained Accessory Power (RAP) Description and Operation»(/chevrolet/chevy-express-g3500/1996-2012/remont/accessories-control-systems/#retained-accessory-power-system) .
Visual/Physical Inspection
- Inspect for aftermarket devices which could affect the operation of the Retained Accessory Power system. Refer to «Checking Aftermarket Accessories»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__checking-aftermarket-accessories) in Wiring Systems.
- Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
Intermittent
Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Symptom List
Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom
- «Retained Accessory Power (RAP) On After Timeout»(/chevrolet/chevy-express-g3500/1996-2012/remont/accessories-control-systems/#retained-accessory-power-system__retained-accessory-power-rap-on-after)
- «Retained Accessory Power (RAP) Inoperative»(/chevrolet/chevy-express-g3500/1996-2012/remont/accessories-control-systems/#retained-accessory-power-system__retained-accessory-power-rap-inoperative)
Retained Accessory Power (RAP) On After Timeout
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Retained Accessory Power (RAP) Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems | |||
| 1 | Did you review the retained accessory power (RAP) diagnostic starting point? | Go to Step 2 | Go to Diagnostic Starting Point - Retained Accessory Power |
| 2 | Install a scan tool. Observe all door jamb/lift gate switches, with the scan tool. Open and close each door. Does the scan tool display change from active to inactive? | Go to Step 3 | Go to Diagnostic System Check - Lighting Systems in Lighting Systems |
| 3 | Close all of the doors. Turn the ignition switch to the ON position, then to the OFF position. Wait 10 minutes. Attempt to operate the power windows. Do the power windows operate after the 10 minute timer expires? | Go to Step 4 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems |
| 4 | Remove the WND RAP relay. Do the power windows operate? | Go to Step 5 | Go to Step 6 |
| 5 | Repair the short to voltage at the WND RAP relay output circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 7 | |
| 6 | Replace the WND RAP relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems. Did you complete the repair? | Go to Step 7 | |
| 7 | Operate the system in order to verify the repair. Does RAP power mode function normally? | System OK | Go to Step 2 |
Retained Accessory Power (RAP) On After Timeout
Retained Accessory Power (RAP) Inoperative
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Retained Accessory Power (RAP) Schematics Connector End View Reference: Master Electrical Component List in Wiring System | |||
| 1 | Did you perform the Diagnostic System Check - Retained Accessory Power (RAP)? | Go to Step 2 | Go to Diagnostic System Check - Retained Accessory Power |
| 2 | Close the driver and passenger doors. Turn ON the ignition, with the engine OFF. Turn OFF the ignition. Do the retained accessory power functions (power windows, power sunroof) operate normally? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring System | Go to Step 3 |
| 3 | Disconnect the WND RAP relay. Connect a test lamp between the WND RAP relay control circuit and the WND RAP relay ground circuit. Close the driver and passenger doors. Turn ON the ignition, with the engine OFF. Turn OFF the ignition. Does the test lamp illuminate? | Go to Step 5 | Go to Step 4 |
| 4 | Test the WND RAP relay control circuit and ground circuit for opens. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 7 |
| 5 | Connect a test lamp between the WND RAP relay supply voltage circuit and the WND RAP relay ground circuit. Does the test lamp illuminate? | Go to Step 8 | Go to Step 6 |
| 6 | Repair the open in the WND RAP relay supply voltage circuit. Did you complete the repair? | Go to Step 11 | |
| 7 | Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Testing for Intermittent Conditions and Poor Connections in Wiring System. Did you find and correct the condition? | Go to Step 11 | Go to Step 10 |
| 8 | Test the WND RAP relay output circuit for a short to ground or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 9 |
| 9 | Replace the WND RAP relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems. Did you complete the replacement? | Go to Step 11 | |
| 10 | IMPORTANT: Perform the setup procedure for the new BCM. Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control Systems. Replace the BCM. Refer to Body Control Module Replacement in Body Control Systems.Did you complete the replacement? | Go to Step 11 | |
| 11 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3 |
| IMPORTANT |
|---|
| Perform the setup procedure for the new BCM. Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control Systems. |
Retained Accessory Power (RAP) Inoperative
Retained Accessory Power (RAP) Power Mode
RAP is a power mode that permits the operation of some accessories for up to 10 minutes after the ignition switch is turned OFF. The RAP power mode is enabled by the body control module (BCM).
The BCM
- Controls certain body functions.
- Sends out a class 2 message via the serial data link, which enables/disables other modules at the beginning/end of the RAP power mode.
Some BCM features, such as the interior courtesy lamps will function after the 10 minute RAP time limit has elapsed. This is normal, and does not mean the RAP power mode is malfunctioning. The BCM enables the following functions in RAP Power Mode
- The right and left power windows through the WND RAP relay.
- Any class 2 module that functions in RAP power mode and is not connected to the WND RAP relay, is controlled by the BCM via class 2 power mode messages. EXAMPLE: The radio works in RAP power mode because the BCM sends it a class 2 message telling it that the power mode is RAP.
RAP is disabled when
- A door is opened.
- Low battery voltage is detected by the BCM.
- The ignition switch transitions from OFF to ON or ACC.
- 10 minutes have elapsed after the ignition was turned OFF.
The BCM monitors the ignition switch position, battery voltage and passenger compartment door status to determine whether RAP power mode should be enabled. If the ignition switch transitions from ON to OFF, the battery voltage is within the acceptable range, and the passenger compartment doors are closed, the BCM enables RAP power mode. After 10 minutes have elapsed, the BCM sends a class 2 message to the serial data network. This message commands the other modules that are power moded by the BCM to stop functioning.
WND RAP Relay
The BCM controls the WND RAP relay's coil circuit using high side drive. The output of the relay is used to supply battery voltage to the power windows. The WND RAP relay also provides voltage to the power windows when the Accessory power mode is selected.
See also:
• Diagnostic System Check - Door Systems
• Scan Tool Does Not Power Up
• Body Control System Description and Operation
• Diagnostic Trouble Code (DTC) List
• Diagnostic Trouble Code (DTC) List
• DTC B1480
• Testing for Intermittent Conditions and Poor Connections
• Master Electrical Component List
• Circuit Testing
• Wiring Repairs
• Connector Repairs
• Relay Replacement (Within an Electrical Center)
• Checking Aftermarket Accessories
• Retained Accessory Power (RAP) Description and Operation
• Retained Accessory Power (RAP) Schematics
• Retained Accessory Power (RAP) On After Timeout
• Retained Accessory Power (RAP) Inoperative
• Diagnostic Starting Point - Retained Accessory Power