P1487
DTC P1485-P1487
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 P1485
- Cooling Fan Output Circuit
DTC P1486
- Cooling Fan Output Circuit Low Voltage
DTC P1487
- Cooling Fan Output Circuit High Voltage
Circuit/System Description
The hybrid powertrain control module 2 (HPCM 2) controls the radiator cooling fans with a pulse width modulated (PWM) signal to the cooling fan control modules. The HPCM 2 supplies a regulated 12 volts to the engine control module (ECM) via the cooling fan output circuit. The ECM modulates the output circuit to ground to request operation of the engine radiator cooling fans in response to predetermined internal combustion engine (ICE) coolant temperatures. The HPCM 2 uses the request from the ECM, along with other inputs such as the need for power electronics, high voltage battery, or HVAC cooling to determine the total percentage of cooling fan operation in a range of 0-100 percent. The ECM cooling fan output circuit is controlled with a solid state device called a driver. The driver is equipped with a feedback circuit which is pulled up to a voltage within the controller. The ECM can determine if the output circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage.
Conditions for Running the DTC
* DTC P2537 is not set.
* The 12 V battery voltage is equal to or greater than 11 V.
* The accessory circuit is active for greater than 5 seconds.
* DTCs P1485, P1486, and P1487 run continuously when the conditions above are met.
Conditions for Setting the DTC
The ECM detects that the commanded state of the driver and the actual state of the output circuit do not match for greater than 5 seconds.
Action Taken When the DTC Sets
DTCs P1485, P1486 and P1487 are type B DTCs.
Conditions for Clearing the DTC
DTCs P1485, P1486 and P1487 are type B DTCs.
Diagnostic Aids
DTCs P1485, P1486 and P1487 will not keep the cooling fans from operating. If one of these DTCs is set the HPCM 2 commands the cooling fans to 90%. If the cooling fans do not operate, refer to Cooling Fan Malfunction - DTC P148A-P148C P148A for further diagnosis.
Reference Information
Schematic Reference
Engine Cooling Schematics [1][2]Cooling System
Connector End View Reference
Component Connector End Views Hybrid/EV Battery Pack X1 A4
Description and Operation
* Hybrid Modes of Operation Description Hybrid Modes of Operation Description
* Hybrid Cooling System Description and Operation Hybrid Cooling System 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
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Control Module Referencesfor scan tool information
Circuit/System Verification
1. Ignition ON, engine operating. Observe the DTC information with a scan tool. DTC P1485, P1486, or P1487 should not be set.
2. Service Mode active, command the cooling fans from OFF to 90%, with a scan tool, using the ECM Control Functions menu.
3. Observe the scan tool parameters listed below:
* Cooling Fan Control Circuit Open Test Status
* Cooling Fan Control Circuit Low Voltage Test Status
* Cooling Fan Control Circuit High Voltage Test Status
Each of the parameters should display OK or Not Run when changing between the commanded states.
4. Operate the vehicle within the conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
Danger: The Volt Battery Pack will utilize an exchange program. Please consult the most recent revision of bulletin/PI #PIP4841, available in Service Information (SI), for a list of approved Volt Battery Pack service procedures. Components that may be removed and serviced without exchanging the complete battery pack are identified in the bulletin/PI. Please contact the GM Technical Assistance Center (1-877-446-8227) if you have any questions.
1. Ignition OFF, disconnect the X2 harness connector at the K114B HPCM 2.
Note: The cooling fan output circuit is pulled-up to a voltage within the ECM. 3-4 V measured on this circuit with the HPCM 2 harness connector disconnected is normal.
2. Service Mode active, test for 3-4 V between the ECM cooling fan output circuit terminal X2-9 and ground.
• If less than the specified range, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
• If greater than the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.
3. If all circuits test normal, replace the K114B HPCM 2.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
Control Module References Control Module Referencesfor engine control module or hybrid powertrain control module 2 replacement, programming and setup