For 1990-2009 cars
ABS Components
Antilock Brake System Schematics
Handling ESD Sensitive Parts Notice

### Circuit Description

The wheel speed sensor generates an AC signal. The signal is produced when a toothed ring passes the wheel speed sensor. The frequency of the AC signal is proportional to the wheel speed. The EBCM uses the frequency of the signal in order to calculate the wheel speed.

### Conditions for Running the DTC

• | No wheel speed sensor circuit hardware malfunctions are present.

• | ABS is not active.

• | The brake switch is OFF.

### Conditions for Setting the DTC

DTC C0051 will set when the EBCM detects a sudden change in the right rear wheel speed determined to be unreasonable.

### Action Taken When the DTC Sets

• | The EBCM disables the ABS

• | The ABS warning indicator turns ON

### Conditions for Clearing the DTC

• | The condition responsible for setting the DTC no longer exists

• | The Scan Tool Clear DTCs function is used

• | The vehicle is driven at 24km/h (15 mph)

### Diagnostic Aids

Inspect for the following when diagnosing this part of the Antilock Brake System (ABS):

• | Loose right rear wheel speed sensor

• | Worn right rear suspension and or drivetrain components

• | Right rear wheel speed sensor physically damaged

• | Right rear wheel speed sensor reluctor wheel toothed ring damaged

Perform a careful visual inspection of the following items:

• | The right rear wheel speed sensor toothed ring

• | The right rear wheel bearing

• | The right rear wheel speed sensor

An intermittent malfunction is most likely caused by a poor connection rubbed thorough wire insulation or a wire that is broken inside the insulation.

If the customer comments reflect that the ABS indicator lamp is ON only during humid conditions (rain, snow, vehicle wash), thoroughly inspect the right rear wheel speed sensor circuitry for signs of water intrusion.

Thoroughly inspect any circuitry that is suspected or causing the intermittent complaint for the following conditions:

• | Backed-out terminals

• | Improper mating

• | Broken locks

• | Improperly formed or damaged terminals

• | Poor terminal to wiring connections

• | Physical damage to the wiring harness

| Important: Wheel speed sensor resistance increases with an increase in sensor temperature. When measuring for a short to ground in a wheel speed sensor wiring circuit, manually switch the J 39200 (Digital Multimeter) to the Meg-Ohms range. This will ensure a high resistance short to ground can be found. See J 39200 owners manual.

Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems if an intermittent malfunction exists.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step tests the wheel speed sensor for the proper resistance value.

2. This step ensures that the wheel speed sensor generates the proper voltage.

3. This step tests whether the wheel speed sensor circuits are shorted together.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform A Diagnostic System Check - ABS? | -- | Go to Step 2 | Go to Diagnostic System Check - ABS
2 |

1. Install a scan tool.
2. Turn ON the ignition.
3. Set up the scan tool Snap Shot feature to trigger for this DTC.
4. Drive the vehicle at a speed greater than the specified value.

Does the scan tool indicate that this DTC set?

8 km/h (5 mph)

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

3 |

1. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
2. Disconnect the wheel speed sensor connector.
3. Measure the resistance across the wheel speed sensor.

Does the resistance measure within the specified range?

1120-2520 ohms

Go to Step 4

Go to Step 8

4 |

1. Spin the wheel.
2. Measure the AC voltage across the wheel speed sensor.

Does the AC voltage measure greater than the specified value?

100 mV

Go to Step 5

Go to Step 8

5 | Inspect for poor connections at the harness connector of the wheel speed sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 6
6 | Test the wheel speed sensor circuits for the following:

• | An open

• | A short to ground

• | A short to voltage

• | Shorted together

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 10

Go to Step 7

7 | Inspect for poor connections at the harness conector for the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9
8 | Replace the wheel speed sensor. Refer to Front Wheel Speed Sensor Replacement or Rear Wheel Speed Sensor Replacement . Did you complete the replacement? | -- | Go to Step 10 | --
9 | Replace the Brake Modulator Assembly. Refer to Brake Pressure Modulator Valve Assembly Replacement . Did you complete the replacement? | -- | Go to Step 10 | --
10 |

1. Use the scan tool in order to clear the DTCs.
2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK