C0857

DTC C0857 or C1242

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 C0857 00
- Device Ignition Accessory Circuit Low

DTC C1242 00
- Electronic Brake Control Module Ignition Accessory Switch Circuit Low Voltage

Diagnostic Fault Information






Circuit/System Description

The hybrid powertrain control module 2 sends the serial data wake-up power mode status in a serial data message to the electronic brake control module (EBCM). The hybrid powertrain control module 2 also powers up the serial data wake-up circuit to the EBCM when the vehicle power mode is Vehicle ON or Vehicle in Service Mode.

Conditions for Running the DTC

* Hybrid powertrain control module 2 is awake
* Vehicle power mode is Vehicle ON or Vehicle in Service Mode
* Battery energy control module is awake
* System voltage greater than 9 V

Conditions for Setting the DTC

* Hybrid powertrain control module 2 is awake
* Ignition input is active, and 500 ms after the ignition input transitions high, a voltage below 5 V is detected 3 consecutive times

Action Taken When the DTC Sets

No action is taken.

Conditions for Clearing the DTC

* The current DTC will clear when the malfunction is no longer present.
* A history DTC clears when the module power mode cycle counter reaches the reset threshold of 40, without a repeat of the malfunction.

Diagnostic Aids

A short to voltage in the serial data wake-up circuit will keep the vehicle modules awake, which can drain the vehicle's battery.

Reference Information
Schematic Reference

Data Communication Schematics [1][2]Electrical Diagrams
Connector End View Reference

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

Power Mode Description and Operation Power Mode
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 Testing

1. Disconnect the harness connector at the K17 electronic brake control module.
2. Vehicle OFF, verify that a test lamp does not illuminate between the serial data wake-up circuit terminal 12 and ground.

• If the test lamp illuminates, test the serial data wake-up circuit for a short to voltage. If the circuit tests normal, replace the K114B hybrid powertrain control module 2.

3. Vehicle in Service Mode, verify that a test lamp illuminates between the serial data wake-up circuit terminal 12 and ground.

• If the test lamp does not illuminate, test the serial data wake-up circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K114B hybrid powertrain control module 2.

4. If all circuits test normal, replace the K17 electronic brake control module.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

Control Module References Programming and Relearning for the appropriate control module replacement, programming and setup