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

### Circuit Description

As a toothed ring passes by the wheel speed sensor, changes in the electromagnetic field cause the wheel speed sensor to produce an AC voltage signal. The frequency of the AC voltage signal is proportional to the wheel speed. The amplitude of the AC voltage signal is directly related to wheel speed and the proximity of the wheel speed sensor to the toothed ring. The proximity of the wheel speed sensor to the toothed ring is also referred to as the air gap.

### Conditions for Setting the DTC

DTC C1234 can set anytime after initialization.

A malfunction exists if either of the left rear wheel speed sensor circuits are open or shorted to voltage or ground.

### Action Taken When the DTC Sets

• | A malfunction DTC stores.

• | The ABS disables.

• | The ABS warning indicator turns ON.

### Conditions for Clearing the DTC

• | The condition responsible for setting the DTC no longer exists and the Scan Tool Clear DTCs function is used.

• | 100 drive cycles pass with no DTCs detected. A drive cycle consists of starting the vehicle, driving the vehicle over 16 km/h (10 mph), stopping and then turning the ignition OFF.

### Diagnostic Aids

The following conditions may cause an intermittent malfunction:

• | A poor connection

• | Rubbed-through wire insulation

• | A broken wire inside the insulation

Use the enhanced diagnostic function of the Scan Tool in order to measure the frequency of the malfunction.

If the customer's comments reflect that the amber ABS warning indicator is ON only during moist environmental changes (rain, snow, vehicle wash), inspect all the wheel speed sensor circuitry 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 five percent saltwater solution.

Add two teaspoons of salt to twelve ounces of water to make a five percent saltwater solution.

2. Test drive the vehicle over various road surfaces (bumps, turns, etc.) above 24 km/h (15 mph) for at least 30 seconds.
3. If the DTC returns, replace the suspected harness.

Thoroughly inspect any circuitry that may be 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

Resistance of the wheel speed sensor will increase with an increase in sensor temperature.

Use the following procedure when replacing a wheel speed sensor or harness:

1. Inspect the wheel speed sensor terminals and harness connector for corrosion and/or water intrusion.
2. Replace the wheel speed sensor and jumper harness if evidence of corrosion or water intrusion exists.

Refer to On-Vehicle Service in this section.

### Test Description

1. This test checks the wheel speed sensor circuitry for proper resistance values at the EBCM.

2. This test checks for a short to ground in the wheel speed sensor signal low circuitry

3. This test checks for a short to voltage in either the high or the low wheel speed sensor signal circuits.

4. This test determines if the wheel speed sensor signal low is shorted to voltage.

5. This test determines if the wheel speed sensor signal high is shorted to voltage.

6. This test determines if the malfunction is caused by the EBCM.

7. This test checks for an open or high resistance in the wheel speed sensor signal low circuitry.

8. This test checks for an open or high resistance in the wheel speed sensor signal high circuitry.

9. This test checks the wheel speed sensor for the proper resistance value.

10. This test checks for an intermittent short to ground in the wheel speed sensor signal high circuitry.

11. This test checks for an intermittent short to ground in the wheel speed sensor signal low circuitry.

12. This test checks for a short to ground in the wheel speed sensor.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Important: Zero the J 39200 test leads before making any resistance measurements. Refer to the J 39200 user's manual. Important: Difficulty may occur when trying to locate intermittent malfunctions in the wheel speed sensor circuit. Do not disturb any of the electrical connections. Change the electrical connections only when instructed to do so by a step in the diagnostic table. Changing the electrical connections at the correct time will ensure that an intermittent electrical connection will not be corrected until the source of the malfunction is found.
1 | Was the ABS Diagnostic System Check performed? | -- | Go to Step 2 | Go to Diagnostic System Check - ABS
2 |

1. Turn the ignition switch to the OFF position.
2. Make a 5 percent saltwater solution.
3. Thoroughly spray the left rear wheel speed sensor harness with the saltwater solution.
4. Disconnect the EBCM harness connector.
5. Use the J 39200 in order to measure the resistance between the EBCM harness connector terminal 10 and the EBCM harness connector terminal 23.

Is the resistance within the specified range?

1044-1276 ohms

Go to Step 3

Go to Step 11

3 | Use the J 39200 in order to measure the resistance between the EBCM harness connector terminal 23 and ground. Is the resistance within the specified range? | OL (Infinite) | Go to Step 4 | Go to Step 14
4 |

1. Turn the ignition switch to the ON position.

Do not start the engine.

2. Use the J 39200 in order to measure the voltage between the EBCM harness connector terminal 23 and ground.

Is the voltage within the specified range?

0-1 V

Go to Step 7

Go to Step 5

5 |

1. Turn the ignition switch to the OFF position.
2. Disconnect the left rear wheel speed sensor at the left rear wheel speed sensor connector.
3. Turn the ignition switch to the ON position.

Do not start the engine.

4. Use the J 39200 in order to measure the voltage between the EBCM harness connector terminal 23 and ground

Is the voltage within the specified range?

0-1 V

Go to Step 6

Go to Step 19

6 | Use the J 39200 in order to measure the voltage between the EBCM harness connector terminal 10 and ground. Is the voltage within the specified range? | 0-1 V | Go to Step 31 | Go to Step 20
7 |

1. Turn the ignition switch to the OFF position.
2. Inspect the following terminals:

• | The EBCM harness connector terminal 10

• | The EBCM harness connector terminal 23

• | The remaining terminals of the EBCM connector

3. Inspect the above terminals for the following conditions:

• | Terminal damage

• | Poor terminal contact

• | Terminal corrosion

• | Terminal damage, terminal corrosion, and poor terminal contact may cause an open circuit, a short to voltage, or a short to ground.

Are there signs of poor terminal contact, terminal corrosion, or damaged terminals?

--

Go to Step 27

Go to Step 8

8 | Inspect the wiring of CKT 885 and CKT 884 for signs of wire damage. Wire damage may cause the following conditions in CKT 885 and CKT 884:

• | An open circuit

• | A short to voltage

• | A short to ground

Are there signs of damaged wiring?

--

Go to Step 21

Go to Step 9

9 | Inspect the harness connectors of CKT 885 and CKT 884 for signs of wire damage. Wire damage may cause the following conditions in CKT 885 and CKT 884:

• | An open circuit

• | A short to voltage

• | A short to ground

Are there signs of damaged connectors?

--

Go to Step 22

Go to Step 10

10 |

1. Reconnect the EBCM harness connector.
2. Reconnect the left rear wheel speed sensor harness connector.
3. Install a Scan Tool .
4. Test drive the vehicle at a speed above 24 km/h (15 mph) for at least 30 seconds.
5. Use the Scan Tool in order to read the DTCs.

Does DTC C1234 set as a current DTC?

--

Go to Step 30

Go to Step 31

11 |

1. Disconnect the left rear wheel speed sensor directly at the left rear wheel speed sensor connector.
2. Use the J 39200 in order to measure the resistance between the EBCM harness connector terminal 23 and the left rear wheel speed sensor harness connector terminal B.

Is the resistance within the specified range?

0-2 ohms

Go to Step 12

Go to Step 23

12 | Use the J 39200 in order to measure the resistance between the EBCM harness connector terminal 10 and the left rear wheel speed sensor harness connector terminal A. Is the resistance within the specified range? | 0-2 ohms | Go to Step 13 | Go to Step 24
13 | Use the J 39200 in order to measure the resistance between the left rear wheel speed sensor connector terminal A and the left rear wheel speed sensor connector terminal B. Is the resistance within the specified range? | 1044-1276 ohms | Go to Step 31 | Go to Step 28
14 |

1. Disconnect the connector C413
2. Use the J 39200 in order to measure the resistance between the EBCM harness connector terminal 23 and ground.

Is the resistance within the specified range?

OL

(Infinite)

Go to Step 15

Go to Step 25

15 | Use the J 39200 in order to measure the resistance between the EBCM harness connector terminal 10 and ground. Is the resistance within the specified range? | OL (Infinite) | Go to Step 16 | Go to Step 26
16 |

1. Thoroughly respray the left rear wheel speed sensor harness with the saltwater solution.
2. Disconnect the left rear wheel speed sensor directly at the left rear wheel speed sensor.
3. Use the J 39200 in order to measure the resistance between the left rear wheel speed sensor harness connector terminal A and ground.

Is the resistance within the specified range?

OL

(Infinite)

Go to Step 17

Go to Step 29

17 | Use the J 39200 in order to measure the resistance between the left rear wheel speed sensor harness connector terminal B and ground. Is the resistance within the specified range? | OL (Infinite) | Go to Step 18 | Go to Step 29
18 | Use the J 39200 in order to measure the resistance between the left rear wheel speed sensor connector terminal A and ground. Is the resistance within the specified range? | OL (Infinite) | Go to Step 31 | Go to Step 28
19 | Repair the short to voltage in CKT 885. Refer to Wiring Repairs in Wiring Systems. If the short to voltage is found in the left rear wheel speed sensor harness, replace the left rear wheel speed harness. Refer to Wheel Speed Sensor Jumper Harness Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

20 | Repair the short to voltage in CKT 884. Refer to Wiring Repairs in Wiring Systems. If the short to voltage is found in the left rear wheel speed sensor harness, replace the left rear wheel speed harness. Refer to Wheel Speed Sensor Jumper Harness Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

21 | Repair the wiring damage in CKT 885 or CKT 884. Refer to Wiring Repairs in Wiring Systems. If the wiring damage is found in the left rear wheel speed sensor harness, replace the left rear wheel speed harness. Refer to Wheel Speed Sensor Jumper Harness Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

22 | Repair the connector damage in CKT 885 or CKT 884. Refer to Wiring Repairs in Wiring Systems. If the connector damage is found in the left rear wheel speed sensor harness, replace the left rear wheel speed harness. Refer to Wheel Speed Sensor Jumper Harness Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

23 | Repair the open or high resistance in CKT 885. Refer to Wiring Repairs in Wiring Systems. If the open or high resistance is found in the left rear wheel speed sensor harness, replace the left rear wheel speed harness. Refer to Wheel Speed Sensor Jumper Harness Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

24 | Repair the open or high resistance in CKT 884. Refer to Wiring Repairs in Wiring Systems. If the open or high resistance is found in the left rear wheel speed sensor harness, replace the left rear wheel speed harness. Refer to Wheel Speed Sensor Jumper Harness Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

25 | Repair the short to ground in CKT 885. Refer to Wiring Repairs in Wiring Systems. If the short to ground is found in the left rear wheel speed sensor harness, replace the left rear wheel speed harness. Refer to Wheel Speed Sensor Jumper Harness Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

26 | Repair the short to ground in CKT 884. Refer to Wiring Repairs in Wiring Systems. If the short to ground is found in the left rear wheel speed sensor harness, replace the left rear wheel speed harness. Refer to Wheel Speed Sensor Jumper Harness Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

27 | Replace all of the terminals and the connectors that exhibit signs of poor terminal contact, corrosion, or damaged terminals. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check - ABS | --
28 | Replace the left rear wheel speed sensor. Refer to Wheel Speed Sensor Replacement . Is the repair complete? | -- | Go to Diagnostic System Check - ABS | --
29 | Replace the left rear wheel speed sensor harness. Refer to Wheel Speed Sensor Jumper Harness Replacement . Is the repair complete? | -- | Go to Diagnostic System Check - ABS | --
30 | Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Is the repair complete? | -- | Go to Diagnostic System Check - ABS | --
31 |

• | The malfunction is intermittent or not present at this time.

• | Inspect all of the connectors and the harnesses for damage that could cause the following conditions:

- | An open or a high resistance

- | A short to ground

- | A short to voltage

• | The sensor harness must be replaced if the sensor harness is damaged.

• | Refer to Diagnostic Aids for more information.

Is the action complete?

--

System OK

--