P15B9
DTC P15B9 or P15BA
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructionsprovides an overview of each diagnostic category.
DTC Descriptors
DTC P15B9 00
- Ignition RUN/Crank Switch Circuit Low Voltage
DTC P15BA 00
- Ignition RUN/Crank Switch Circuit High Voltage
Diagnostic Fault Information
Circuit/System Description
The body control module (BCM) controls the RUN/CRNK relay through the control circuit by applying voltage to the circuit. The ignition RUN/CRNK is energized when the ignition switch is in ON or START, or when a remote start is requested. The hybrid powertrain control module 2 sends the RUN/Crank power mode status in a serial data message to the HVAC control module. The RUN/Crank circuit is powered up in the RUN/Crank power mode.
Conditions for Running the DTC
P15BA 00
* System voltage between 9-16 V.
* Vehicle power mode is OFF or Crank Request.
P15B9 00
* System voltage between 9 and 16 V.
* Vehicle power mode is ACC or RUN.
* The DTC can only run when the output is activated.
Conditions for Setting the DTC
P15BA 00
RUN/Crank output is not active and a short to battery is detected 3 consecutive times.
P15B9 00
* RUN/Crank output is active and a short to ground is detected 3 consecutive times.
* RUN/Crank output is not active and an open circuit is detected 20 consecutive times.
Action Taken When the DTC Sets
P15B9 00
* The RUN/Crank output is deactivated when a short to ground is detected. After 100 ms the output is activated again. This happens 3 times and then the output is deactivated until a new RUN/Crank request is received.
* Open: No action is taken.
P15BA 00
No action is taken.
Conditions for Clearing the DTC
* The current DTC will clear when the malfunction is no longer present during a DTC check.
* A history DTC clears when the module ignition cycle counter reaches the reset threshold of 40, without a repeat of the malfunction.
Diagnostic Aids
* A short to voltage in the RUN/CRNK relay control circuit will cause the malfunction indicator lamp (MIL) to illuminate with the ignition key OFF, and the engine will remain running if started and the ignition key is removed.
* A short to voltage in the RUN/Crank control circuit will keep the vehicle bus awake, which can drain the vehicle's battery.
* A short to ground in the extension of this circuit through the body control module can back feed to the keyless entry control module. Check for a short to ground on the RUN/Crank circuit on the other side of the RUN/Crank pass thru, in the body control module, before replacing the body control module.
Reference Information
Schematic Reference
* Body Control System Schematics [1][2]Body Control Systems
* Power Distribution Schematics Power Distribution Schematics
Connector End View Reference
Component Connector End Views Hybrid/EV Battery Pack X1 A4
Description and Operation
Power Mode Description and Operation Power Mode
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module Referencesfor scan tool information
Circuit/System Testing
1. Ignition OFF, disconnect the KR73 RUN/CRNK relay.
2. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 10 ohm between the relay ground circuit and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify that a test lamp illuminates between the relay B+ circuit and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
4. Connect a test lamp between the relay control circuit and ground.
5. Cycle the ignition ON and OFF. The test lamp should turn ON and OFF when changing S39 ignition switch positions.
• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.
• If the test lamp is always OFF, test the control circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the K9 BCM.
6. If all circuits test normal, test or replace the KR73 RUN/CRNK relay.
Component Testing
1. Ignition OFF, disconnect the KR73 RUN/CRNK relay.
2. Test for 70-150 Ohms between terminals 85 and 86.
• If the resistance is not within the specified range, replace the KR73 RUN/CRNK relay.
3. Test for infinite resistance between the following terminals:
* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87
• If less than specified, replace the KR73 RUN/CRNK relay.
4. Install a 3 A fused jumper wire between relay terminal 86 and 12 V. Install a jumper wire between relay terminal 85 and 86. Measure for less than 5 Ohms between terminals 87 and 85.
• If greater than specified, replace the KR73 RUN/CRNK relay.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Relay Replacement (Attached to Wire Harness) Relay Replacement (Attached to Wire Harness)Relay Replacement (Within an Electrical Center) Relay Replacement (Within an Electrical Center)
* Control Module References Control Module Referencesfor BCM replacement, programming and setup