Diagnostic Instructions
DTC Descriptors
DTC B1477: Retained Accessory Power Circuit Low
DTC B1478: Retained Accessory Power Circuit High
Diagnostic Fault Information
Circuit
| Short to Ground
| Open/High Resistance
| Short to Voltage
| Signal Performance
|
RAP relay coil control
| B1477
| B1477
| B1478
| --
|
Circuit/System Description
The body control module (BCM) controls the RAP relay. The relay allows the BCM to control the application of power to the feed circuits of multiple subsystems and components. When the ignition switch is in either the ACC or the ON position, the BCM energizes
the relay by providing ground to the RAP relay coil control circuit. The BCM also energizes the relay for a specific time after the ignition key is removed providing a set of specific conditions are met. Refer to retained accessory power (RAP) description and
operation for more information on RAP.
Conditions for Running the DTC
Battery voltage is 9-16 volts.
Conditions for Setting the DTC
B1477
| • | The BCM detects an open or a short to ground in the RAP relay coil control circuit when the RAP relay is not energized. |
| • | The condition above must be present for more than 1 second. |
B1478
| • | The BCM detects a short to voltage in the RAP relay coil control circuit when the BCM is trying to energize the RAP relay. |
| • | The condition above must be present for more than 1 second. |
Action Taken when the DTC Sets
| • | The BCM stores the DTC in memory. |
| • | The devices powered by the relay will not operate if the relay control circuit is open or shorted to B+. |
| • | The devices powered by the relay will be able to be operated beyond the time limit if the relay control circuit is shorted to ground. |
Conditions for Clearing the DTC
| • | A current DTC clears when the malfunction is no longer present. |
| • | A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction. |
Diagnostic Aids
| • | An open or short to ground between the fuses and subsystems will only effect the individual subsystem. Refer to the specific system for diagnostics. |
| • | A short to voltage will backfeed through all fuses and effect all subsystems connected to the controlled circuit of the RAP relay |
Reference Information
Schematic Reference
Power Moding Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Retained Accessory Power Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the RAP relay.
- Connect a test lamp between the relay coil control circuit terminal 86 and B+.
- With the driver door open, cycle the ignition ON and OFF. The test lamp should turn ON and OFF when changing ignition switch positions.
| ⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM. |
| ⇒ | If the test lamp is always OFF, test the control circuit for a short to voltage or open/high resistance. If the circuit tests normal, replace the BCM. |
- If the test lamp illuminates normal, test or replace the RAP relay.
Component Testing
Relay Test
- Ignition OFF, disconnect the RAP relay.
- Test for 70-110 ohms between terminals 85 and 86.
| ⇒ | If the resistance is not within the specified range, replace the relay. |
- Test for infinite resistance between the following terminals:
| ⇒ | If less specified, replace the relay. |
- Install a 20-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 5 ohms of resistance between terminals 30 and 87.
| ⇒ | If greater than specified, replace the relay. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the repair.
