Chevrolet Silverado / GMC Sierra. Service manual — part 706

DTC C0040 18

Right Front Wheel Speed Sensor Circuit Signal Amplitude Below Minimum

Diagnostic Fault Information

Circuit/System Description

The wheel speed sensor receives ignition voltage from the electronic brake control module
(EBCM) and provides a DC square wave signal back to the module. As the wheel spins, the
EBCM uses the frequency of the square wave signal to calculate the wheel speed.

Conditions for Running the DTC

C0035 00 or C0040 00

The ignition is ON.

Ignition voltage is greater than 9.5 volts.

C0035 5A or C0040 5A

The ignition is ON.

Ignition voltage is greater than 9.5 volts.

The brake pedal is not pressed.

A DTC is not set for the other wheel speed circuit on the same axle.

Conditions for Setting the DTC

An erratic signal output of the wheel speed sensor is detected.

A short to ground, open/high resistance is detected on the wheel speed sensor signal circuit.

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Performance

Left Front Sensor Signal Circuit

C0035 02

-

C0035 05

C0035 18, 0F

Left Front Sensor 12 volt
Reference Circuit

-

C0035 05

-

C0035 18, 0F

Right Front Sensor Signal
Circuit

C0040 02

-

C0040 05

C0040 18,0F

Right Front Sensor 12 volt
Reference Circuit

-

C0040 05

-

C0040 18, 0F

2008 Chevrolet Silverado 1500

2008 BRAKES Antilock Brake System - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

A short to voltage, short to ground or an open/high resistance is detected on the low
reference circuit.

Wheel speed sensor power supply is less than 7.6 volts.

A missing wheel speed sensor signal

Action Taken When the DTC Sets

The EBCM disables the Antilock Brake System (ABS)/Traction Control System (TCS) and
VSES for the duration of the ignition cycle.

The electronic brake distribution (EBD) does not function optimally.

The ABS indicator turns ON.

The Traction Control indicator turns ON.

The driver information center (DIC) displays the Service Stability System message.

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present.

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

Diagnostic Aids

Inspect the back of the wheel bearing on the encoder surface for metal debris that could
cause an erratic reading with the sensor. Do not use a magnet to clean the debris, or damage
to the encoder ring may occur.

If 2 or more wheel speed sensors are inoperative diagnose each wheel speed sensor
individually.

An ECE 13 response may be required, after repairs are made, and DTCs are cleared,
operate the vehicle at speeds greater than 15 km/h (10 mph) to complete the self test, and
the EBCM will turn off the ABS indicator.

If the customer comments that the ABS indicator is ON only during moist environmental
conditions: rain, snow, vehicle wash, etc., inspect the wheel speed sensor wiring for signs of
water intrusion. If the DTC is not current, clear all DTCs and simulate the effects of water
intrusion by using the following procedure:

1. Spray the suspected area with a 5 percent saltwater solution. To create a 5 percent saltwater

solution, add 2 teaspoons of salt to 8 fl oz of water (10 g of salt to 200 ml of water).

2. Test drive the vehicle over various road surfaces: bumps, turns, etc., above 40 km/h (25

2008 Chevrolet Silverado 1500

2008 BRAKES Antilock Brake System - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

mph) for at least 30 seconds.

3. Rinse the area thoroughly when completed.

Reference Information

Schematic Reference

Antilock Brake System Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

ABS Description and Operation (With JL4) or ABS Description and Operation (Without
JL4)

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 Verification

Observe the scan tool Wheel Speed Sensor parameter. The reading should be the same speed on
all sensors when driving in a straight line at a speed greater than 20 km/h (13 mph).

Circuit/System Testing

With JF3/JF7

It is recommended that Component Testing is performed before Circuit Testing when diagnosing
wheel speed sensors.

2008 Chevrolet Silverado 1500

2008 BRAKES Antilock Brake System - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

1. Ignition OFF, disconnect the harness connector at the EBCM.

2. Ignition ON, test for less than 1 volt between the low reference circuit terminals of the

appropriate sensor listed below and ground.

LF Sensor circuit terminal 22

RF Sensor circuit terminal 6

If greater than the specified value, test the low reference circuit for a short to voltage.
If the circuit tests normal, replace the EBCM.

3. Test for less than 1 volt between the signal circuit terminals of the appropriate sensor listed

below and ground.

LF Sensor circuit terminal 34

RF Sensor circuit terminal 18

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

4. Ignition OFF, test for infinite resistance between the low reference terminals of the

appropriate sensor listed below and ground.

LF Sensor circuit terminal 22

RF Sensor circuit terminal 6

If less than the specified value, test the low reference circuit for a short to ground. If
the circuit tests normal, test or replace the wheel speed sensor.

5. Test for infinite resistance between the following signal circuit terminals of the appropriate

sensor listed below and ground.

LF Sensor circuit terminal 34

RF Sensor circuit terminal 18

If less than the specified value, test the signal circuit for a short to ground. If the circuit
tests normal, test or replace the wheel speed sensor.

6. Ignition OFF, disconnect the harness connector at the appropriate WSS.

7. Test for less than 2 ohms between the appropriate low reference circuit terminals listed

below.

LF Sensor circuit terminals 22 at the EBCM harness connector, and terminal 1 at the
WSS harness connector

RF Sensor circuit terminals 6 at the EBCM harness connector, and terminal 1 at the
WSS harness connector

If greater than the specified value, test the low reference circuit for an open or high
resistance. If the circuit tests normal, test or replace the wheel speed sensor.

8. Test for less than 2 ohms between the appropriate signal circuit terminals listed below.

2008 Chevrolet Silverado 1500

2008 BRAKES Antilock Brake System - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado