For 1990-2009 cars only
Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptor
DTC C0870: Device Voltage Reference Output 1 CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Brake Pressure Sensor Signal | C0870 | -- | C0870 | -- |
Brake Fluid Pressure Sensor 5-Volt Reference Circuit | C0870 | C0870 | C0870 | -- |
Brake Fluid Pressure Sensor Ground Circuit | -- | C0870 | -- | -- |
Circuit Description
The brake pressure sensor reference voltage is monitored for an over or under voltage condition.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The vehicle speed is greater than 40 km/h (25 mph). |
Conditions for Setting the DTC
A malfunction is detected if the supply voltage is above 5.6 volts or below 4.4 volts for more than 60 milliseconds.
Action Taken When the DTC Sets
| • | A malfunction DTC is set. |
| • | The ABS, traction control system (TCS) and vehicle stability enhancement system (VSES) are disabled. |
| • | The ABS, SERVICE VEHICLE SOON and Stability Off lamp indicators are ON. |
Conditions for Clearing the DTC
| • | The condition for the DTC is no longer present. |
| • | A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present. |
| • | Using a scan tool. |
| • | The electronic brake control module (EBCM) automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles. |
Diagnostic Aids
Possible causes of this DTC are the following conditions:
| • | An open in the pressure sensor supply voltage circuit. |
| • | A short to ground in the pressure sensor supply voltage circuit. |
| • | A short to B+ in the pressure sensor supply voltage circuit. |
Reference Information
Schematic Reference
Antilock Brake System Schematics
Connector End View Reference
Antilock Brake System Connector End Views
Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for Scan Tool Information
Circuit/System Verification
Ignition ON, observe the scan tool
Circuit/System Testing
- Ignition OFF, disconnect the EBCM harness connector at the brake fluid pressure sensor.
- With a DMM test for less than 5.0 ohms of resistance between the brake fluid pressure sensor low reference circuit terminal 1 and ground.
- Ignition ON, with a DMM test for 4.4-5.6 volts between the brake fluid pressure sensor 5-volt reference circuit terminal 3 and ground.
- With the DMM, verify the brake pressure sensor signal range is less than 4.4 volts.
- Install a 3A fused jumper wire between the brake fluid pressure sensor signal circuit terminal 2 and the brake fluid pressure sensor 5-volt reference circuit terminal 3. With a DMM verify the voltage value is greater than 5.6 volts.
- If all circuits test normal, test or replace the brake fluid pressure sensor.
| ⇒ | If greater than the specified range, with the DMM test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the EBCM. |
| ⇒ | If less than the specified range, with the DMM test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the EBCM. |
| ⇒ | If greater than the specified range, with the DMM test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the EBCM. |
| ⇒ | If greater than the specified value, test the signal circuit terminal 2 for a short to voltage. If the circuit tests normal, replace the EBCM. |
| ⇒ | If less than the specified value, test the signal circuit terminal 2 for a short to ground or an open/high resistance. If the circuit tests normal, replace the EBCM. |
Component Testing
- Install a 3A fused jumper wire between the brake fluid pressure sensor 5-volt reference terminal 3 and 5 volts. Install a jumper wire between the low reference terminal 1 and ground.
- Sweep the sensor through the entire range while monitoring the resistance between the signal circuit terminal 2 and the low reference circuit terminal 1. The voltage should vary between 4.4-5.6 volts without any spikes or dropouts.
| ⇒ | If not within the specified range or is erratic, replace the brake fluid pressure sensor. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM or EBCM replacement, setup, and programming |
