Stop_Start System Malfunction

Stop/Start System Malfunction Diagnostic Instructions Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Review Strategy Based Diagnosis for an overview of the diagnostic approach. Diagnostic Procedure Instructions provides an overview of each diagnostic category. Diagnostic Fault Information

Circuit Number	Circuit Function	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performan
8040	B+	4	4	—	—
8140	B+	4	4	—	—
4320	Ignition	4	4	—	—
1111	Signal	1	1	1	—
625	Control	4	4	—	—
1110	Control	2	2	3	—
2172	Control	4	4	—	—
2173	Control	4	4	—	—
1851	Ground	—	1, 2	—	—
250	Ground	—	4	—	—
1. Stop/Start switch inoperative 2. Stop/Start switch indicator inoperative 3. Stop/Start switch indicator always on 4. Some components and modules will not operate properly

Circuit/System Description The T19 Multifunction Power Supply Converter is supplied voltage through B+ circuit 8040 and B+ circuit 8140. Ground is provided by ground circuit 250, of which there are two redundant circuits. The T19 Multifunction Power Supply Converter is used to maintain constant battery voltage to necessary components during an auto engine stop/start event. At the T19 Multifunction Power Supply Converter, the B+ circuit 8040 provides voltage to control circuit 2172 and the B+ circuit  8140 provides voltage to control circuit 2173. The K20 Engine Control Module commands the KR27 Starter Relay by providing voltage on the control circuit 625. The T19 Multifunction Power Supply Converter monitors control circuit 625 as an indicator that the K20 Engine Control Module has commanded the engine to start, ending the auto engine stop/start event. During the engine start, the T19 Multifunction Power Supply Converter will supply voltage on control circuit 2172 and control circuit 2173, which provides critical components and control module a stable voltage during the engine start event. The T19 Multifunction Power Supply Converter communicates voltage on control circuit 2172 and control circuit 2173 to the K20 Engine Control Module on the powertrain CAN bus. The K20 Engine Control Module compares voltage on ignition circuit 439 voltage to the indicated voltage received from the T19 Multifunction Power Supply Converter to determine if there is a system fault. The S86 Vehicle Stability Control System Switch incorporates the auto stop/start disable switch which will disable the auto stop/start system when the switch is pressed and released, the system will be enabled again if the switch is pressed and released or the ignition is cycled off and back on. The auto stop/start disable switch is a hard wired to the K9 Body Control Module. When the switch is pressed the signal circuit 1111 is grounded though the switch ground circuit 1851, when the auto stop/start system is disabled the K9 Body Control Module circuit 1110 sends a pulse with modulated voltage to illuminate the indicator, the indicator is grounded through the switch by ground circuit 1851. Diagnostic Aids If an excessive parasitic draw is present the auto stop/start system may be inoperative and a prevent a successful Battery Sensor learn from being performed. Devices causing additional battery loads when the vehicle is off may reduce the state of charge, and may disable the stop/start system. Refer to Checking Aftermarket Accessories Short trips that prevent the battery to fully charge, or the fluids to reach full operating temperature and may disable the stop/start system. Refer to: Stop/Start Disable, Inhibit, and Restart Reasons Autostop disable reason information can be reviewed with the scan tool. Reference Information Schematic Reference Starting and Charging Schematics Connector End View Reference Master Electrical Component List Description and Operation Stop/Start System Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs DTC Type Reference Powertrain Diagnostic Trouble Code (DTC) Type Definitions Scan Tool Reference Control Module References for scan tool information Circuit/System Verification

1. Ignition ON.

Note

A low or high voltage DTC may set in multiple control modules due to a concern with the battery or charging system.

2. Verify there are no system voltage DTCs set as current or history in any control module. ⇒ If any system voltage DTCs are set Diagnose these DTCs first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle. ⇓ If no system voltage DTCs are set
3. Ignition Off and all vehicle systems OFF.

Note

The battery voltage should stabilize after a few minutes of turning the ignition/vehicle Off.

4. Verify the battery voltage is within 12.4 V to 12.8 V at the C1 Battery. ⇒ If not within the specified range Refer to Battery Inspection/Test ⇓ If within the specified range
5. Engine Running with all accessories off, allow the system voltage to stabilize.
6. Test for 13 V to 15 V at the C1 Battery. ⇒ If not within the specified range Refer to Charging System Test
7. Verify the disable switch Indicator turns on and off when pressing and releasing the stop/start select switch. ⇒ If the Indicator does not turn on and off Refer to Circuit/System – Stop/Start Switch Malfunction ⇓ If the Indicator turns on and off
8. Verify the scan tool parameters Battery Sensor Module state of Charge Error is less than 10%. ⇒ If not the specified state 8.1. Perform the Battery Sensor Module learn. Refer to Battery Sensor Module Learn 8.2. After performing the Battery Sensor learn road test the vehicle and verify the Stop/Start system operates. ⇒ If a condition exists, review the scan tool Autostop Disable Reason. Refer to Stop/Start Disable, Inhibit, and Restart Reasons. ⇓ If no condition exists 8.3. A fault is not currently present and may be an intermittent condition. ⇓ If the specified state
9. Road test the vehicle and verify the Stop/Start system operates. ⇒ If a condition exists If a condition exists review the scan tool Autostop Disable Reason. Refer to Stop/Start Disable, Inhibit, and Restart Reasons. ⇓ If no condition exists
10. Operate the vehicle allowing a vehicle Auto Stop/Start event to occur.
11. Verify the infotainment system, HVAC system, instrument cluster, shift lever, park brake switch, and the left and right steering wheel controls continue to operate without interruption. ⇒ If a condition exists Refer to Circuit/System – Stop/Start System Malfunction ⇓ If no condition exists
12. A fault is not currently present and may be an intermittent condition. Circuit/System Testing Stop/Start Switch Malfunction
13. Ignition OFF, disconnect the X3 electrical connector at the K9 Body Control Module, ignition ON.
14. Verify the auto stop/start disable indicator on the auto stop/start disable switch is not illuminated. ⇒ If the auto stop/start disable indicator is illuminated Repair the short to voltage on circuit 1110 ⇓ If the auto stop/start disable indicator is not illuminated
15. Test for infinite resistance between signal circuit terminal 23 and ground. ⇒ If less than infinite resistance 3.1. Test circuit 1111 for a short to ground. ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 3.2. Replace the S86 Vehicle Stability Control System Switch. ⇓ If infinite resistance
16. Test for less than infinite resistance between signal circuit terminal 23 and ground while pressing and holding the auto stop/start disable switch. ⇒ If infinite resistance 4.1. Test circuit 1851 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit or ground connection. ⇓ If an open/high resistance is not found 4.2. Test circuit 1111 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 4.3. Ignition On Vehicle in Service Mode. 4.4. Test Circuit 1111 for a short to voltage. ⇒ If Short to voltage is found repair the fault on the circuit. ⇓ If Short to voltage is not found 4.5. Replace the S86 Vehicle Stability Control System Switch. ⇓ If less than infinite resistance
17. Connect a B+ 3 A fused jumper wire between control circuit terminal 15 and B+.
18. Verify the auto stop/start disable indicator on the auto stop/start disable switch is illuminated. ⇒ If the auto stop/start disable indicator is not illuminated 6.1. Test circuit 1110 for a short to ground. ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 6.2. Test circuit 1110 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 6.3. Replace the S86 Vehicle Stability Control System Switch. ⇓ If the auto stop/start disable indicator is illuminated
19. Replace the K9 Body Control Module. Stop/Start System Malfunction

Note

Circuit/System Verification must be performed before proceeding with Circuit/System Testing. If the DTC set only as a history DTC, do not replace any components.

1. Ignition Off, disconnect the connector at the T19 Multifunction Power Supply Converter.
2. Verify a test lamp illuminates between ground circuit terminal 7 and B+. ⇒ If the test lamp does not illuminate Repair the open/high resistance on circuit 250 or the ground connection. ⇓ If the test lamp illuminates
3. Verify a test lamp illuminates between ground circuit terminal 12 and B+. ⇒ If the test lamp does not illuminate Repair the open/high resistance on circuit 250 or the ground connection. ⇓ If the test lamp illuminates
4. Verify a test lamp illuminates between B+ circuit terminal 11 and ground. ⇒ If the test lamp does not illuminate and the circuit fuse is good 4.1. Test circuit 8040 for an open/high resistance. ⇒ if an open/high resistance is found, repair the fault on the circuit. ⇓ If an open or high resistance is not found 4.2. Verify the fuse is not open and there is voltage at the fuse. ⇒ If the test lamp does not illuminate and the circuit fuse is open 4.1. Test circuit 8040 for a short to ground ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 4.2. Test circuit 2172 for a short to ground ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 4.3. Replace the T19 Multifunction Power Supply Converter. ⇓ If the test lamp illuminates
5. Using the schematics, identify and remove any fuses powered by control circuit 2172.
6. Test for less than 1 V between control circuit terminal 10 and ground. ⇒ If 1  or greater Repair the short to voltage on circuit 2172. ⇓ If less than 1 V
7. Ignition OFF.
8. Test for infinite resistance between control circuit terminal 10 and ground. ⇒ If less than infinite resistance Repair the short to ground on circuit 2172. ⇓ If infinite resistance
9. Verify a test lamp illuminates between B+ circuit terminal 8 and ground. ⇒ If the test lamp does not illuminate and the circuit fuse is good 9.1. Test circuit 8140 for an open/high resistance. ⇒ if an open/high resistance is found, repair the fault on the circuit. ⇓ If an open or high resistance is not found 9.2. Verify the fuse is not open and there is voltage at the fuse. ⇒ If the test lamp does not illuminate and the circuit fuse is open 9.1. Test circuit 8140 for a short to ground ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 9.2. Test circuit 2173 for a short to ground ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 9.3. Replace the T19 Multifunction Power Supply Converter. ⇓ If the test lamp illuminates
10. Using the schematics, identify and remove any fuses powered by control circuit 2173.
11. Test for less than 1 V between control circuit terminal 9 and ground. ⇒ If 1  or greater Repair the short to voltage on circuit 2173. ⇓ If less than 1 V
12. Ignition OFF.
13. Test for infinite resistance between control circuit terminal 9 and ground. ⇒ If less than infinite resistance Repair the short to ground on circuit 2173.
14. Ignition ON.
15. Verify a test lamp illuminates between terminal 4 and ground. ⇒ If the test lamp does not illuminate 15.1. Test circuit 4320 for an open/high resistance. ⇒ if an open/high resistance is found, repair the fault on the circuit. ⇓ If an open or high resistance is not found 15.2. Test circuit 4320 for a short to ground ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 15.3. Replace the K20 Engine Control Module. ⇓ If the test lamp turns illuminates
16. Ignition Crank.
17. Verify a test lamp illuminates between terminal 5 and ground while the engine is cranking. ⇒ If the test lamp does not illuminate 17.1. Test circuit 625 for an open/high resistance. ⇒ if an open/high resistance is found, repair the fault on the circuit. ⇓ If an open or high resistance is not found 17.2. Test circuit 625 for a short to ground ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 17.3. Replace the K20 Engine Control Module. ⇓ If the test lamp illuminates
18. Replace the T19 Multifunction Power Supply Converter. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Multifunction Power Supply Converter Replacement for T19 Multifunction Power Supply Converter replacement Vehicle Stability Control System Switch Replacement For control module replacement, programming, and setup refer to Control Module References