Chevrolet Trax: DTC C027B: Brake booster vacuum sensor/brake booster vacuum pump
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 Descriptors
DTC C025E
Brake Booster Vacuum Sensor Circuit
DTC C027B
Brake Booster Electric Vacuum Pump
For symptom byte information refer to Symptom Byte List .
Diagnostic Fault Information
Circuit/System Description
The brake booster vacuum sensor measures the vacuum in the brake booster. The
electronic brake control
module supplies a 5 v reference and a low reference circuit to the brake booster
vacuum sensor. The vacuum
sensor supplies a voltage signal in relation to the pressure in the brake
booster to the electronic brake control
module. When the vacuum within the system becomes low, the electronic brake
control module turns on the
brake booster pump motor by providing battery voltage to the brake booster pump
motor relay. The relay
activates and supplies the voltage to the brake booster pump motor.
Conditions for Running the DTC
Engine running
Conditions for Setting the DTC
C025E 01
- A short to voltage is detected on the signal circuit.
- A short to voltage is detected on the 5 V reference circuit.
- A short to voltage is detected on the relay control circuit.
C025E 04
- A open/high resistance is detected on the vacuum sensor signal circuit.
- A open/high resistance is detected on the relay control circuit.
C025E 5A
The Electronic Brake Control Module detected an erratic Vacuum Sensor Signal
that is not plausible.
C025E 71
The electronic brake control module receives an invalid serial data message
from the engine control module
C027B 01
The electronic brake control module receives an invalid serial data message
from the engine control module.
C027B 04
The electronic brake control module receives an invalid serial data message
from the engine control module.
Action Taken When the DTC Sets
- The ABS indicator turns ON.
- The red Brake warning indicator turns ON.
- The Electronic Brake Control Module disables the ABS, the traction
control, and the electronic stability
control for the duration of the ignition cycle.
Conditions for Clearing the DTC
- A current DTC clears when the diagnostic runs and passes.
- The history DTC will clear after 40 consecutive fault-free ignition
cycles have occurred.
Reference Information
Schematic Reference
Hydraulic Brake Schematics (Encore), Hydraulic Brake Schematics (Trax)
Connector End View Reference
WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS -
INDEX - ENCORE WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT
CONNECTOR END VIEWS - INDEX - TRAX
Description and Operation
Brake Assist System 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
C025E 71
- Ignition ON.
- Verify that no other DTCs are set.
- If any other DTCs are set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle .
- Replace the K20 Engine Control Module.
- Verify the DTC C025E does not set while operating the vehicle under the
conditions for Running the
DTC.
Replace the K17 Electronic Brake Control Module.
- All OK.
C025E 01, C025E 04, C025E 5A, C027B 01, or C027B 04
- Ignition OFF and all vehicle systems OFF, disconnect the KR14 Brake
Booster Pump Motor Relay. It
may take up to 2 min for all vehicle systems to power down.
- Test for less than 10 ohms between the ground circuit terminal 1 (86)
and ground.
If 10 ohms or greater
- Ignition OFF.
- Test for less than 2 ohms in the ground circuit end to end.
- If 2 ohms or greater, repair the open/high resistance in the circuit.
- If less than 2 ohms, repair the open/high resistance in the ground
connection.
If less than 10 ohms
- Ignition ON.
- Verify a test lamp illuminates between the B+ circuit terminal 3 (30)
and ground.
- If the test lamp does not illuminate and the circuit fuse is good
- Ignition OFF.
- Test for less than 2 ohms in the B+ circuit end to end.
- If 2 ohms or greater, repair the open/high resistance in the circuit.
- If less than 2 ohms, verify the fuse is not open and there is voltage at
the fuse.
If the test lamp does not illuminate and the circuit fuse is open
- Ignition OFF.
- Test for infinite resistance between the B+ circuit and ground.
- If less than infinite resistance, repair the short to ground on the
circuit.
- If infinite resistance
- Test for infinite resistance between the control circuit terminal 5 (87)
and ground.
- If less than infinite resistance, repair the short to ground on the
circuit.
- If infinite resistance, replace the KR14 Brake Booster Pump Motor Relay.
If the test lamp illuminates
- Connect a test lamp between the control circuit terminal 2 (85) and the
ground circuit terminal 1 (86).
Clear EBCM DTCs.
- Verify the test lamp turns ON and OFF when commanding the Brake Booster
Electric Vacuum Pump ON
and OFF with a scan tool.
If the test lamp is always OFF
- Ignition OFF, disconnect the harness connector at the K17 Electronic
Brake Control Module.
- Test for infinite resistance between the control circuit and ground.
- If less than infinite resistance, repair the short to ground on the
circuit.
- If infinite resistance
- Test for less than 2 ohms in the control circuit end to end.
- If 2 ohms or greater, repair the open/high resistance in the circuit.
- If less than 2 ohms, replace the K17 Electronic Brake Control Module.
If the test lamp is always ON
- Ignition OFF, disconnect the harness connector at the K17 Electronic
Brake Control Module,
ignition ON.
- Test for less than 1 V between the control circuit and ground.
- If 1 V or greater, repair the short to voltage on the circuit.
- If less than 1 V, replace the K17 Electronic Brake Control Module.
If the test lamp turns ON and OFF
- Verify that a test lamp does not illuminate between the control circuit
terminal 5 (87) and ground.
- If the test lamp illuminates
Repair the short to voltage on the control circuit
If the test lamp does not illuminate
- Ignition OFF and all vehicle systems OFF, disconnect the harness
connector at the M9 Brake Booster
Pump Motor. It may take up to 2 min for all vehicle systems to power down.
- Test for less than 10 ohms between the M9 Brake Booster Pump Motor
ground circuit terminal 2 and
ground.
If 10 ohms or greater
- Ignition OFF.
- Test for less than 2 ohms in the ground circuit end to end.
- If 2 ohms or greater, repair the open/high resistance in the circuit.
- If less than 2 ohms, repair the open/high resistance in the ground
connection.
If less than 10 ohms
- Connect the harness connector at the M9 Brake Booster Pump Motor.
- Ignition ON, connect a 30 A fused jumper wire between the B+ circuit
terminal 3 (30) and the control
circuit terminal 5 (87) .
- Verify the M9 Brake Booster Pump Motor is activated.
If the M9 Brake Booster Pump Motor does not activate
- Ignition OFF, disconnect the harness connector at the M9 Brake Booster
Pump Motor.
- Test for less than 2 ohms in the control circuit end to end.
- If 2 ohms or greater, repair the open/high resistance in the circuit.
- If less than 2 ohms, replace the M9 Brake Booster Pump Motor.
If the M9 Brake Booster Pump Motor activates
- Test for 60-180 ohms between terminals 85 and 86 on the relay.
- If less than 60 or greater than 180 ohms
Replace the relay.
If between 60-180 ohms
- Test for infinite resistance between the terminals listed below
- 30 and 86
- 30 and 85
- 30 and 87
- 85 and 87
- If less than infinite resistance
Replace the relay.
If infinite resistance
- Install a 20 A fused jumper wire between relay terminal 85 and 12 V.
Install a jumper wire between relay
terminal 86 and ground.
- Test for less than 2 ohms between terminals 30 and 87.
If 2 ohms or greater
Replace the relay.
If less than 2 ohms
- Ignition OFF and all vehicle systems OFF, disconnect the harness
connector at the B19B Brake Booster
Vacuum Sensor. It may take up to 2 min for all vehicle systems to power down.
- Test for less than 10 ohms between the low reference circuit terminal 2
and ground.
If 10 ohms or greater
- Ignition OFF, disconnect the harness connector at the K17 Electronic
Brake Control Module.
- Test for less than 2 ohms in the low reference circuit end to end.
- If 2 ohms or greater, repair the open/high resistance in the circuit.
- If less than 2 ohms, replace the K17 Electronic Brake Control Module.
If less than 10 ohms
- Ignition ON.
- Test for 4.8-5.2 V between the 5 V reference circuit terminal 3 and
ground.
If less than 4.8 V
- Ignition OFF, disconnect the harness connector at the K17 Electronic
Brake Control Module.
- Test for infinite resistance between the 5 V reference circuit and
ground.
- If less than infinite resistance, repair the short to ground on the
circuit.
- If infinite resistance
- Test for less than 2 ohms in the 5 V reference circuit end to end.
- If 2 ohms or greater, repair the open/high resistance in the circuit.
- If less than 2 ohms, replace the K17 Electronic Brake Control Module.
If greater than 5.2 V
- Ignition OFF, disconnect the harness connector at the K17 Electronic
Brake Control Module,
ignition ON.
- Test for less than 1 V between the 5 V reference circuit and ground.
- If 1 V or greater, repair the short to voltage on the circuit.
- If less than 1 V, replace the K17 Electronic Brake Control Module.
If between 4.8-5.2 V
- Ignition OFF, disconnect the harness connector at the K17 Electronic
Brake Control Module, Ignition
ON.
- Test for less than 1 V between the B19B Brake Booster Vacuum Sensor
signal circuit terminal 1 and
ground.
If greater than 1 V
Repair the short to voltage on the circuit.
If less than 1 V
- Ignition OFF.
- Test for infinite resistance between the B19B Brake Booster Vacuum
Sensor signal circuit terminal 1 and
ground.
If less than infinite resistance
Repair the short to ground on the circuit.
If infinite resistance
- Test for less than 2 ohms in the B19B Brake Booster Vacuum Sensor signal
circuit end to end.
If 2 ohms or greater
Repair the open/high resistance in the circuit.
If less than 2 ohms
- Replace the B19B Brake Booster Vacuum Sensor.
- Verify the DTC does not set while operating the vehicle under Conditions
for Running the DTC.
If the DTC sets
Replace the K17 Electronic Brake Control Module.
If the DTC does not set
- All OK.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
- Power Brake Booster Vacuum Hose Replacement for brake booster vacuum
sensor replacement
- Control Module References for control module replacement, programming
and setup.
READ NEXT:
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.
Diag
NOTE: The following steps must be completed before using the
symptom tables.
Perform the Brake System Vehicle Road Test before using the hydraulic
brake symptom tables in order
to duplicate the
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.
Diag
SEE MORE:
Stripes or Decals
The stripes and decals adhere to a painted surface using pressure sensitive
adhesive.
The use of a wetting solution aids the technician in lifting and positioning the
stripe or decal during the
installation. The wetting solution ensures a better bond between the stripe or
decal
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
DT