C1242

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. Vehicle OFF, disconnect the harness connector at the K17 electronic brake control module.

2. Connect a test lamp between the serial data wake-up circuit terminal 12 and ground.

3. Verify the test lamp turns ON and OFF when cycling the S83 vehicle ON/OFF switch between Vehicle in Service Mode and Vehicle OFF.

• If the test lamp is always OFF

1. Vehicle OFF.

2. Test for infinite resistance between the serial data wake-up circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance.

3. Test for less than 2 ohms in the serial data wake-up circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K114B hybrid powertrain control module 2.

• If the test lamp is always ON

1. Vehicle OFF.

2. Test for less than 1 V between the ignition circuit and ground.

• If 1 V or greater, repair the short to voltage on the circuit.

• If less than 1 V, replace the K114B hybrid powertrain control module 2.

• If the test lamp turns ON and OFF

4. Test or 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