P0AF8
DTC P0AF8 or P0AFB
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 Instructions) 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 wake-up 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 conductor 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 conductor open
* Possible Hybrid Battery Pack ground cable or connection
Reference Information
Schematic Reference
* Hybrid Controls Schematics (Hybrid Controls Schematics)
* Hybrid Energy Storage Schematics ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Starter/Generator Description and Operation (Description and Operation)
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 (Programming and Relearning) for scan tool information
Circuit/System Verification
P0AF8
1. If DTC is history, refer to Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections).
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 (Testing for Intermittent Conditions and Poor Connections).
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 conductor 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.