For 1990-2009 cars
ABS Components
Antilock Brake System Schematics

### Circuit Description

The toothed wheel generates a voltage pulse as it moves past the sensor. Each tooth-gap-tooth series on the wheel generates a pulse. The EBTCM uses the frequency of these pulses to determine the wheel speed. The amplitude of the voltage generated in each pulse depends on the air gap between the sensor and the toothed wheel and depends on wheel speed.

### Conditions for Setting the DTC

• | Damaged or missing teeth on one or more of the wheel speed sensor rings.

• | Noise on one or more of the wheel speed sensor signals.

• | The EBTCM cannot specifically identify which wheel speed sensor is causing the malfunction. If the EBTCM can define the specific speed sensor causing the malfunction, the DTC associated with the sensor (DTC 39, 42, 44, or 46) will be set concurrent with or instead of DTC 25.

### Action Taken When the DTC Sets

• | A malfunction DTC is stored.

• | The ABS and the TC indicator lamps are turned on.

• | The ABS and the TCS are disabled.

### Conditions for Clearing the DTC

• | The condition for the DTC is no longer present.

• | The scan tool Clear DTCs function is used.

• | 100 drive cycles have passed with no DTCs detected.

### Diagnostic Aids

Check the toothed wheel for any large grooves, gouges, marks, etc. that might influence the tooth's signal at the wheel speed sensor. Also check for a buildup of foreign material in the gaps between teeth in the toothed wheel, as the material may cause this malfunction.

A worn hub/bearing assembly may cause this fault in extreme cases. The bearing play allows the sensor-to-toothed-ring gap to change excessively.

### Test Description

The number(s) below refer to the step numbers on the diagnostic table.

1. If DTC 39, 42, 44 or 46 is set current or history, the DTC set is likely the sensor that has set DTC 25.

2. This step checks if the spark plug wires and wheel speed sensor wiring are in close proximity to each other.

3. If the scan tool can record any erroneous wheel speed signal, diagnose those sensors first.

#### DTC 25 - Wheel Sensor Circuit Frequency Malfunction

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Diagnostic System Check performed? | -- | Go to Step 2 | Go to A Diagnostic System Check
2 | Is the following DTC(s) set concurrently with DTC 25:

• | Is DTC 39 set concurrently with DTC 25?

• | Is DTC 42 set concurrently with DTC 25?

• | Is DTC 44 set concurrently with DTC 25?

• | Is DTC 46 set concurrently with DTC 25?

--

Go to the Appropriate Diagnostic Table

Go to Step 3

3 |

1. Turn the ignition switch to the OFF position.
2. Inspect all the wheel speed sensor rings for the following:

• | Inspect for missing teeth.

• | Inspect for large grooves.

• | Inspect for large gouges.

• | Inspect for buildup of foreign material in the gaps between the teeth.

3. Inspect for a worn hub bearing assembly for a front sensor or inspect for a worn inner axle bearing for a rear sensor which could allow the sensor to toothed ring gap to change excessively.

Is the damage evident?

--

Go to Step 9

Go to Step 4

4 | Check for proper routing of the wheel speed sensor wiring. Check that the wheel speed sensor wiring is away from the spark plug wires. Improper routing of the wheel speed sensor wiring could cause Electromagnetic Interference (EMI). Is the wheel speed sensor properly routed? | -- | Go to Step 5 | Go to Step 10
5 |

1. Install the scan tool.
2. Turn the ignition switch to the RUN position.
3. Set the scan tool to Snapshot Manual Trigger Mode.
4. Trigger the Snapshot while test driving the vehicle above 40 km/h (25 mph).

Did the scan tool show any erroneous wheel speed signals?

--

Go to the Appropriate Wheel Speed Sensor Circuit Malfunction Diagnostic Table

Go to Step 6

6 |

1. Turn the ignition switch to the OFF position.
2. Inspect all the connectors and terminals for poor terminal contact or corrosion.
3. Inspect the circuits for the following:

• | Inspect the circuits for damage from chafing.

• | Inspect the circuits for tension.

• | Inspect the circuits for misrouting.

Are the following signs evident:

• | Is poor terminal contact evident?

• | Is corrosion evident?

• | Is damage evident?

--

Go to Step 11

Go to Step 7

7 |

1. Reconnect all the connectors.
2. Disconnect the scan tool if previously connected.
3. Test drive the vehicle above 40 km/h (25 mph) for at least 2 minutes.

Did DTC 25 reset?

--

Go to Step 8

Go to A Diagnostic System Check

8 | Replace the EBTCM. Refer to EBTCM Replacement . Is the repair complete? | -- | Go to A Diagnostic System Check | --
9 | Repair the damage. Is the repair complete? | -- | Go to A Diagnostic System Check | --
10 |

1. Reroute the wheel speed sensor wiring away from the spark plug wires.
2. Test drive the vehicle above 40 km/h (25 mph) for at least 2 minutes.

Did DTC 25 reset?

--

Go to Step 8

Go to A Diagnostic System Check

11 | Repair the damaged connector(s) or repair the harness. Refer to Connector Repairs in Wiring Systems. Is the repair complete? | -- | Go to A Diagnostic System Check | --