For 1990-2009 cars

### 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 C1100 00: Base Brake System Pressure Circuit
DTC C1100 01: Base Brake System Pressure Circuit Short to Battery
DTC C1100 02: Base Brake System Pressure Circuit Short to Ground
DTC C1100 08: Base Brake System Pressure Circuit Signal Invalid
DTC C1100 09: Base Brake System Pressure Circuit Rate of Change Above Threshold

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Brake Booster Vacuum Sensor 5-Volt Reference | C1100 02 | C1100 00, 08 | C1100 01 | C1100 08
Signal | C1100 00, 02 | C1100 00 | C1100 00,01 | C1100 09, 08
Low Reference | C1100 00 | C1100 00 | -- | C1100 09, 08

### Circuit/System Description

The electronic brake control module (EBCM) provides a 5-volt reference to the brake booster vacuum sensor. The brake booster vacuum sensor converts the change in vacuum levels in the brake booster into a voltage signal. This signal is sent to the EBCM. The voltage signal ranges, from 0.13-3.30 volts depending on vacuum levels.

### Conditions for Running the DTC

#### C1100 00, 01, 02

• | Ignition ON.

• | 5-volt reference voltage is between 4.8-5.2 volts

#### C1100 08

• | The HCU internal pressure sensor is ok.

• | Vacuum pressure in the brake booster is less than -200mbar.

#### C1100 09

• | 5-volt reference voltage is between 4.8-5.2 volts

• | Brake pedal is not applied

• | Speed is above 6 mph (10kph)

### Conditions for Setting the DTC

#### C1100 00, 01, 02

The EBCM detects a short to voltage, short to ground or open/high resistance.

#### C1100 08, 09

• | After the brake pedal has been applied 3 times during one ignition cycle.

• | The EBCM detects the vacuum sensor reading is not plausible.

### Action Taken When the DTC Sets

#### C1100 00, 01, 02

• | The EBCM disables the vehicle stability enhancement system, the optimized hydraulic boost and traction control

• | A warning message/indicator is illuminated

#### C1100 08, 09

A warning message is illuminated

### Conditions for Clearing the DTC

• | The condition for the DTC is no longer present.

• | The EBCM clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

### Reference Information

#### Schematic Reference

Antilock Brake System Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

ABS Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the brake booster vacuum sensor.
2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal 2 and ground.

⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the EBCM.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 3 and ground.

⇒ | If less than the specified range, 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, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the EBCM.

4. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 3 and the signal circuit terminal 1.

⇒ | If less than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the EBCM.

⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the EBCM.

5. Ignition OFF, disconnect the harness connector at the EBCM.
6. Ignition OFF, test for infinite resistance between the signal circuit terminal 41 and ground.

⇒ | If not the specified value, test the signal circuit for a short to ground.

7. If all circuits test normal, test or replace the power brake booster vacuum sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Power Brake Booster Vacuum Sensor Replacement

• | Control Module References for EBCM replacement, setup, and programming