P0AFB
DTC P0AF8 or P0AFB
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
DTC Descriptors
DTC P0AF8
- Hybrid System Voltage
DTC P0AFB
- Hybrid Battery System Voltage High
Circuit/System Description
P0AF8
The engine control module (ECM) monitors the correlation of the battery energy control module (BECM) battery voltage and the starter generator control module (SGCM) output voltage to detect a 36 volt cable open or fuse/relay failure.
P0AFB
The ECM also monitors to detect an over voltage condition and protect the MOSFET (load dump).
If either one of these conditions is detected, the appropriate DTC will set.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
P0AF8
The 36 volt BECM battery voltage - 36 volt SGCM output voltage is greater than 5 volts for 4 seconds.
P0AFB
* In the hardware, 36 volt over voltage signal from protection circuit (sets above 56 volts, clears below 53 volts) is set for 20 ms.
* In the software, 36 volt output voltage is greater than 50 volts for 5 ms.
Action Taken When the DTC Sets
P0AF8, P0AFB
* Stop PWM (MGU shutdown)
* APM PWM off
Conditions for Clearing the DTC
P0AF8
36-volt voltage from BECM (42 VIN) is greater than 0 volt, main relay is closed, and 42 VIN invalid flag is ON.
P0AFB
* In the hardware, clears 30 seconds after wakeup signal is ON.
* In the software, voltage is normal for 100 ms and main relay is closed.
Diagnostic Aids
P0AF8
* Possible 36 volt battery cable open
* Possible Hybrid Battery Pack fuse open
* Possible Hybrid Battery Pack contactor open
* Possible Hybrid Battery Pack ground cable or connection
P0AFB
* Possible 36 volt battery cable open (load dump)
* Possible Hybrid Battery Pack fuse open
* Possible Hybrid Battery Pack contactor open
* Possible Hybrid Battery Pack ground cable or connection
Reference Information
Schematic Reference
* Hybrid Controls Schematics (Electrical Diagrams)
* Hybrid Energy Storage Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
Scan Tool Reference
Control Module References (Programming and Relearning)
Circuit/System Verification
Warning
To help avoid personal injury, additional precautions must be taken prior to working on the generator control module or the generator starter. After removing the 36V battery cables from the generator battery, remove both engine wiring harness connectors from the generator control module. Wait at least 5 minutes and then remove the generator control module cover. Verify voltage levels at all 36V, 12V, and 3-phase connections, are less than 3 volts using a DMM before proceeding.
Warning
To help avoid personal injury, be careful when working in the vicinity of the generator battery disconnect control module. Internal components will still be live, 36V potential, even when the cover has been opened or removed.
P0AF8
1. If DTC is history, refer to Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics).
2. Ignition ON, observe the scan tool Hybrid Battery System Voltage parameter in the BECM data list and the Hybrid System Voltage parameter in the SGCM data list. The voltage should not differ by more than 5 volts.
• If greater than the specified value, continue with Circuit/System Testing.
P0AFB
1. If DTC is history, refer to Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics).
2. Ignition ON, observe the scan tool Hybrid Battery System Voltage parameter in the BECM data list. The voltage should be less than 50 volts.
• If greater than the specified value , replace the BECM.
Circuit/System Testing
P0AF8
1. Verify the DTC is set as current.
2. Ensure the hood is fully closed. Ignition ON, observe and record the scan tool Hybrid Battery System Voltage parameter in the SGCM data list.
3. Ignition ON, observe and record the scan tool Hybrid Battery System Voltage parameter in the BECM data list, the SGCM and BECM voltage parameters should not differ by more than 5 volts.
• If greater than the specified range, visually inspect the 36 volt cable from the hybrid battery pack to SGCM for damage or an open/high resistance.
• If the 36 volt cable damaged replace the 36 volt cable. Refer to 36-Volt Battery Positive Cable Replacement (36-Volt Battery Positive Cable Replacement).
4. Ignition OFF, remove the generator battery disconnect control module cover. Refer to Hybrid Battery Service Disconnect/Connect (Procedures). Inspect the 36 volt and ground cable connections of the hybrid battery pack.
5. Depress and hold the service disconnect for 20 seconds and measure the voltage at the hybrid battery pack the 36 volt terminal to ground. The voltage should not differ by more than 3 volts from the voltage measured in step 3.
6. Note some vehicles have a plastic cover over this area to be measured that must be removed. Measure the voltage at the hybrid battery pack the 36 volt terminal pack side of contactor to ground. The voltage should not differ by more than 3 volts from the scan tool parameter display in step 5.
• If greater than specified value inspect the hybrid battery pack ground cable for being loose or an open/high resistance, the generator battery fuse for an open.
7. If the ground circuit tests normal, the fuse was not open and voltage differs by more than 3 volts, replace the generator battery disconnect control module.
8. Gain access to the 36 volt output cable and connections at the SGCM refer to 175 Amp Mega Fuse Replacement (175 Amp Mega Fuse Replacement).
9. Inspect the 36 volt output cable and 36 volt connections for being loose, damaged or arcing.
• If damage or arcing is found, replace the 36 volt cable. Refer to 36-Volt Battery Positive Cable Replacement (36-Volt Battery Positive Cable Replacement).
10. If all connections and circuits test normal, replace the SGCM.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* 36-Volt Battery Positive Cable Replacement (36-Volt Battery Positive Cable Replacement)
* Control Module References (Programming and Relearning) for BECM/SGCM replacement, setup, and programming.