Circuit Description
As a toothed ring passes by the wheel speed sensor, changes in the electromagnetic field cause the wheel speed sensor to produce a AC voltage signal. The frequency of the sinusoidal (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 C1221 can set when the vehicle is not in an ABS stop.
A malfunction exists if both of the following conditions occur:
| • | The left front wheel speed sensor input signal equals zero. |
| • | The vehicle's reference speed is greater than 8 km/h (5 mph) |
Action Taken When the DTC Sets
| • | A malfunction DTC stores. |
| • | The ABS/ETS/TCS disables. |
| • | The amber ABS/ETS/TCS warning indicator(s) turn 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 DTC(s) detected. |
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. Refer to the Scan Tool manual for the procedure.
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:
- Spray the suspected area with a five percent saltwater solution.
- Test drive the vehicle over various road surfaces (bumps, turns, etc.) above 24 km/h (15 mph) for at least 30 seconds.
- If the DTC returns, replace the suspected harness.
Add two teaspoons of salt to twelve ounces of water to make a five percent saltwater solution.
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 in order to replace a wheel speed sensor:
- Inspect the wheel speed sensor terminals and harness connector for corrosion and/or water intrusion.
- Replace the wheel speed sensor jumper harness if evidence of corrosion or water intrusion exists.
Refer to Wheel Speed Sensor Jumper Harness Replacement , Wheel Speed Sensor Jumper Harness Replacement , Wheel Speed Sensor Jumper Harness Replacement or Wheel Speed Sensor Jumper Harness Replacement .
Use the following procedure in order to replace the wheel speed sensor jumper harness:
- Inspect the wheel speed sensor terminals for corrosion and/or water intrusion.
- Replace the wheel speed sensor if evidence of corrosion or water intrusion exists.
Refer to Wheel Speed Sensor Replacement , Wheel Speed Sensor Replacement or Wheel Speed Sensor Replacement .
Front Wheel Speed Sensor Resistance
The following table contains resistance values for the front wheel speed sensors at varying temperatures for use in diagnosis. The values are approximate and should be used as a guideline for diagnosis.
Temperature (°C) | Temperature (°F) | Resistance (Ohms) |
|---|---|---|
-34 to 4 | -30 to 40 | 804 to 1066 |
5 to 43 | 41 to 110 | 956 to 1240 |
44 to 93 | 111 to 200 | 112 to 1463 |
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.
Do not disturb any of the electrical connections. Change 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.Step | Action | Value(s) | Yes | No | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Diagnostic System Check performed? | -- | Go to Diagnostic System Check | |||||||||||||||
2 |
Is there any physical damage? | -- | ||||||||||||||||
3 | Inspect the following components for physical damage:
Is there any physical damage? | -- | ||||||||||||||||
4 |
Is the resistance within the specified range? | 1020-1137 ohms at 20°C (68°F) | ||||||||||||||||
5 |
Is the voltage equal to or greater than the specified voltage? | 100 mV | ||||||||||||||||
6 |
Is the resistance within the specified range? | OL (Infinite) | ||||||||||||||||
7 |
Are there signs of poor terminal contact, corrosion, or damaged terminals? | -- | ||||||||||||||||
8 | Inspect the wiring of CKT 873 and CKT 830 for signs of damage that may cause a short between CKT 873 and CKT 830. Are there any signs of damaged wiring? | -- | ||||||||||||||||
9 | Inspect the harness connectors of CKT 873 and CKT 830 for signs of damage that may cause a short between CKT 873 and CKT 830. Are there any signs of damaged connectors? | -- | ||||||||||||||||
10 |
Does DTC C1221 set as a current DTC? | -- | Go to Diagnostic Aids | |||||||||||||||
11 |
Is the speed of the left front wheel speed sensor constantly higher than the speed of the three remaining wheel speed sensors? | -- | ||||||||||||||||
12 | Replace all of the terminals that exhibit signs of poor terminal contact, corrosion, or damaged terminal(s). Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||||||||||
13 | Replace the damaged wiring harness that causes the short between CKT 873 and CKT 830. Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||||||||||
14 | Replace the damaged wiring harness connectors that cause the short between CKT 873 and CKT 830. Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||||||||||
15 | Replace the left front wheel speed sensor jumper harness. Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||||||||||
16 | Replace the left front wheel speed sensor. Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||||||||||
17 | Replace the EBCM/EBTCM. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
