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: Brake Booster Vacuum Sensor Performance
DTC C1100 01: Brake Booster Vacuum Sensor Signal Circuit Shorted to Battery
DTC C1100 02: Brake Booster Vacuum Sensor Signal Circuit Short to Ground
DTC C1100 08: Brake Booster Vacuum Sensor Circuit Signal Invalid
DTC C1100 09: Brake Booster Vacuum Sensor Change Above Threshold

### Diagnostic Fault Information

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

### Circuit/System Description

The brake booster pressure sensor measures the negative air pressure or vacuum reserve in the brake booster assembly. During engine running conditions, the brake booster pressure sensor signal circuit voltage varies, depending on the vacuum reserve internal to the brake booster.

### Conditions for Running the DTC

• | Ignition ON.

• | Ignition voltage is greater than 9 volts.

### 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

The EBCM detects the vacuum sensor reading is not plausible.

### Action Taken When the DTC Sets

A DIC message and/or a warning indicator may be displayed.

The brake booster vacuum assist will be disabled for the remainder of the ignition cycle.

### 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 1 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 1 and the signal circuit terminal 3.

⇒ | 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