2010 Cadillac Truck Escalade ESV AWD V8-6.2L Page 1561
are at about the same voltage, the motor generator battery control module closes the positive contactor.
3. With both the negative and positive contactors closed, the drive motor generator battery control module opens the current limit relay.
Conditions for Running the DTC
P0C77
* Ignition voltage is 9-18 V at the drive motor generator battery control module.
* The current limit relay and negative contactor are commanded closed by the hybrid powertrain control module.
* The terminal voltage is less than 60 V prior to starting the precharge sequence.
P1A20
* Ignition voltage is 9-18 V at the drive motor generator battery control module.
* There are less than 4 hybrid battery voltage sensor faults.
Conditions for Setting the DTC
P0C77
One of the following conditions exist:
* The high voltage DC current is greater than 25 A during precharge.
* Within 20 milliseconds of the start of precharge, hybrid battery calculated voltage and powertrain inverter module terminal voltage are
already within 23 V of each other.
P1A20
140 milliseconds after the start of precharge, hybrid battery calculated voltage and hybrid battery terminal voltage are 23 V apart.
Action Taken When the DTC Sets
* DTCs P0C77 and P1A20 are type C DTCs.
* The hybrid powertrain control module will not command the high voltage contactors closed.
Conditions for Clearing the DTC
DTCs P0C77 and P1A20 are type C DTCs.
Diagnostic Aids
Note: If the high voltage contactors opened while under high current load, replace BOTH high voltage contactors. The following conditions could
cause the high voltage contactors to open while under high current load:
* A collision resulting in supplemental inflatable restraint (SIR) deployment.
* A collision that activates the high voltage circuit impact detection (HVCID) sensor.
* A high voltage circuit impact detection sensor circuit fault that occurs while the vehicle is moving.
* A loss of power or ground to the drive motor generator battery control module while the vehicle is moving.
The precharge time can be affected by the following:
* A long precharge time may be caused by an open 125 A fuse in the manual disconnect lever
* A short precharge time may be caused by a positive high voltage contactor stuck.
* A negative high voltage contactor stuck closed will not affect the precharge sequence.
A long or short precharge time may cause any of the following;
The drive motor generator battery control module will start a precharge wait timer after failing 2 consecutive precharge events. The contactors will
not close until the precharge wait time has timed out.
Reference Information
Schematic Reference
* Hybrid Energy Storage Schematics ()
* Hybrid Controls Schematics ()
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views)
Description and Operation
Drive Motor Battery System Description ()
