P148B

Cooling Fan Malfunction - DTC P148A-P148C

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 P148A
- Cooling Fan Signal Circuit Performance

DTC P148B
- Cooling Fan Signal Circuit Low Voltage

DTC P148C
- Cooling Fan Signal Circuit High Voltage

Circuit/System Description

The hybrid/EV powertrain control module 2 controls the radiator cooling fans. The cooling fans are controlled with a pulse width modulated (PWM) signal. The hybrid/EV powertrain control module 2 diagnoses any faults with the hardwire circuit to the engine control module. The engine control module sends a fan request PWM signal to the hybrid/EV powertrain control module 2 through a hardwire circuit. The hybrid/EV powertrain control module 2 operates in a pass-through mode for the engine control module fan request. The higher the duty cycle the higher the cooling fan speed.

Conditions for Running the DTC

P148A
* The 12 V battery voltage is greater than or equal to 9 V.
* The propulsion system is active.
* The cooling fans are enabled for more than 10 seconds.
* None of the following DTCs are set: P148B, or P148C.
OR
* The 12 V battery voltage is greater than or equal to 9 V.
* The propulsion system is inactive.
* The energy storage system thermal condition request is ActiveCool.
* The cooling fans are enabled for more than 10 seconds.
* None of the following DTCs are set: P148B, or P148C.

P148B

The 12 V battery voltage is greater than or equal to 9 V.

P148C
* The 12 V battery voltage is greater than or equal to 9 V.
* The propulsion system is active.
* The cooling fans are enabled for more than 10 seconds.
* OR
* The 12 V battery voltage is greater than or equal to 9 V.
* The propulsion system is inactive.
* The energy storage system thermal condition request is ActiveCool.
* The cooling fans are enabled for more than 10 seconds.

Conditions for Setting the DTC

P148A

The PWM fan duty cycle request from engine control module (Hardwire) is not within 30% of the requested engine cooling fan speed sent to the hybrid/EV powertrain control module 2 via serial data.

P148B

The hybrid/EV powertrain control module 2 has detected a duty cycle of greater than 97% from the engine control module.

P148C

The hybrid/EV powertrain control module 2 has detected a duty cycle of less than 3% from the engine control module.

Action Taken When the DTC Sets

DTCs P148A, P148B and P148C are type B DTCs.

Conditions for Clearing the DTC

DTCs P148A, P148B and P148C are type B DTCs.

Reference Information
Schematic Reference

Engine Cooling Schematics Engine Cooling Schematics
Connector End View Reference

Component Connector End Views Hybrid/EV Battery Pack X1
Description and Operation

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 Programming and Relearning for scan tool information

Circuit/System Verification

Vehicle in Service Mode, with a scan tool, command the Cooling Fan Motor Command ON. Verify that the Cooling Fan Motor Command is greater than 0% and the cooling fans operate.

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. Vehicle OFF, disconnect the X1 harness connector at the K20 engine control module.
2. Vehicle in Service Mode, test for 4.8-5.2 V between the signal circuit terminal 41 and ground.

• If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K114B hybrid/EV powertrain control module 2.
• If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K114B hybrid/EV powertrain control module 2.

3. If all circuits test normal, replace the K20 engine control module.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

Control Module References Programming and Relearning for engine control module or hybrid/EV powertrain control module 2 replacement, programming and setup