For 1990-2009 cars

### Circuit Description

As the wheel is rotated, the speed sensor produces an AC voltage that increases with wheel speed. The electronic brake control module (EBCM) uses the frequency of the AC signal to calculate the wheel speed. The speed sensor is connected to the EBCM by a twisted pair of wires. Twisting reduces noise susceptibility that may cause a DTC to set.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C1203 Right Front Wheel Speed Sensor Circuit Open or Shorted

### Conditions for Running the DTC

Ignition is in the ON position.

### Conditions for Setting the DTC

EBCM has detected an open, short to ground, or a short to battery on the right front wheel speed circuit.

### Action Taken When the DTC Sets

• | The solenoid relay opens, removing power from the pump motor and solenoids.

• | DTC C1203 is stored.

• | ABS disabled, ABS warning lamp turns ON.

### Conditions for Clearing the DTC

• | If the conditions that set the DTC C1203 are no longer present, the DTC may be cleared by using the proper scan tool.

• | The DTC that has not occurred in 100 drive cycles will be cleared from history data.

### Diagnostic Aids

Thoroughly inspect the wiring and connectors when diagnosing intermittent DTCs. This will include the following:

• | Removal of the protective conduit and inspection of wiring for damage, shorts, and contamination

• | Inspection for improperly formed and/or damaged terminals

• | Checking terminal contact retention force by using a spare male/female terminal

• | Removal of the terminals from the connectors to check for proper terminal to wire crimp

If the driver comments reflect that the ABS warning lamp is ON only during moist environmental changes, such as, rain, snow, vehicle wash, the all wheel speed sensor circuitry should be thoroughly inspected for signs of water intrusion. If the DTC is not current, simulate the effects of water intrusion. Use the following procedure. Spray the suspected area with a 5 percent salt-water solution. Then test drive the vehicle over various road surfaces such as, bumps, turns, etc., above 24 km/h (15 mph). If the DTC sets then replace the suspected harness and/or sensor.

When measuring the wheel speed sensor resistance, ensure the vehicle is at room temperature, since resistance will increase with temperature.

Failure to perform the previous steps carefully and fully can result in misdiagnosis, unnecessary component replacement, and reoccurrence of DTC C1203.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Antilock Brake System Schematics Connector End View Reference: Antilock Brake System Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Turn the ignition switch OFF.
2. Inspect the right front wheel speed sensor, and the jumper harness for physical damage.

Is any physical damage noted?

--

Go to Step 3

Go to Step 4

3 | Repair the damage to the right front wheel speed sensor, and/or jumper harness. Did you find and correct the condition? | -- | Go to Step 24 | --
4 | Test drive the vehicle at various speeds and over various road surfaces. Did DTC C1203 reset? | -- | Go to Step 5 | Go to Diagnostic Aids
5 |

1. Turn the ignition switch OFF, with the vehicle in park or neutral.
2. Raise and suitably support the vehicle.
3. Disconnect the right front jumper harness from the right front wheel speed sensor.
4. Connect an ohmmeter to terminals 2 and 1 of the right front wheel speed sensor.
5. Resistance will vary with temperature.

Is the resistance within the specified range?

800-3000 Ω

Go to Step 7

Go to Step 6

6 | Replace the right front wheel speed sensor. Refer to Front Wheel Speed Sensor Replacement. Did you complete the replacement? | -- | Go to Step 24 | --
7 |

1. The right front jumper harness is still disconnected from the speed sensor.
2. Connect an ohmmeter to terminal 1 of the right front wheel speed sensor and then to body ground.

Is the resistance equal to the specified value?

OL (open circuit)

Go to Step 8

Go to Step 6

8 |

1. Disconnect the electronic brake control module (EBCM) harness from the EBCM.
2. Disconnect the right front jumper harness from the ABS body harness.
3. Connect an ohmmeter to the EBCM harness terminal 2 and then to wheel speed sensor terminal 1.

Is the resistance measured less than the specified value?

2 Ω

Go to Step 10

Go to Step 9

9 | Repair the open or high resistance between terminals 2 and 1. Did you find and correct the condition? | -- | Go to Step 24 | --
10 |

1. The EBCM harness is still disconnected from the EBCM.
2. The right front jumper harness is still disconnected from the body harness.
3. Connect an ohmmeter to the EBCM harness terminal 1 and then to wheel speed sensor terminal 2.

Is the resistance measured less than the specified value?

2 Ω

Go to Step 3

Go to Step 11

11 | Repair the open or high resistance between terminals 1 and 2. Did you find and correct the condition? | -- | Go to Step 24 | --
12 |

1. The EBCM harness is still disconnected from the EBCM.
2. The right front jumper harness is still disconnected from the ABS body harness.
3. Connect a voltmeter to EBCM harness terminals 2 and then to body ground.

Is the voltage less than the specified value?

1 V

Go to Step 14

Go to Step 13

13 | Repair the short to voltage between terminals 2 and 1. Did you find and correct the condition? | -- | Go to Step 24 | --
14 |

1. The EBCM harness is still disconnected from the EBCM.
2. The right front jumper harness is still disconnected from the ABS body harness.
3. Connect a voltmeter to the EBCM harness terminal 1 and then to body ground.

Is the voltage less than the specified value?

1 V

Go to Step 16

Go to Step 15

15 | Repair the short to voltage between terminals 1 and 2. Did you find and correct the condition? | -- | Go to Step 24 | --
16 |

1. The EBCM harness is still disconnected from the EBCM.
2. The right front jumper harness is still disconnected from the ABS body harness.
3. Connect an ohmmeter to the EBCM harness terminal 2 and then to body ground.

Is the resistance measured equal to the specified value?

OL (open circuit)

Go to Step 18

Go to Step 17

17 | Repair the short to ground between terminals 2 and 1. Did you find and correct the condition? | -- | Go to Step 24 | --
18 |

1. The EBCM harness is still disconnected from the EBCM.
2. The right front jumper harness is still disconnected from the ABS body harness.
3. Connect an ohmmeter to the EBCM harness terminal 1 and then to body ground.
4. The right front jumper harness is still disconnected from the ABS body harness.
5. Connect an ohmmeter to the EBCM harness terminal 1 and then to body ground.

Is the resistance measured equal to the specified value?

OL (open circuit)

Go to Step 20

Go to Step 19

19 | Repair the short to ground between terminals 1 and 2. Did you find and correct the condition? | -- | Go to Step 24 | --
20 |

1. The EBCM harness is still disconnected from the EBCM.
2. The right front jumper harness is still disconnected from the ABS body harness.
3. Connect an ohmmeter to the EBCM harness terminal 1 and 2.

Is the resistance measured equal to the specified value?

OL (open circuit)

Go to Step 22

Go to Step 21

21 | Repair the short between the two circuits. Did you find and correct the condition? | -- | Go to Step 24 | --
22 |

1. Replace the right front wheel speed sensor jumper harness.
2. Test drive the vehicle at the various speeds and various road surfaces.

Did the DTC C1203 reset?

--

Go to Step 23

Go to Step 24

23 | Replace the EBCM. Refer to Brake Pressure Modulator Valve Assembly Replacement. Did you complete the replacement? | -- | Go to Step 24 | --
24 |

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