DTC C1225 LF Excessive Wheel Speed Variation. Pontiac Montana 1999

For 1990-2009 cars only

Makes 🢒 Pontiac 🢒 1999 🢒 Montana 🢒 DTC 🢒 DTC C1225 LF Excessive Wheel Speed Variation

ABS Components
Antilock Brake System Schematics

Circuit Description

The rotational movement of the toothed ring past the wheel speed sensor causes a change in the electromagnetic field which produces an AC voltage signal by the wheel speed sensor. 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 C1225 can set when the brake is off.

DTC C1225 detects a situation in which the left front wheel acceleration or deceleration is beyond specified limits.

Action Taken When the DTC Sets

•	A malfunction DTC stores.

•	The ABS/TCS disables.

•	The amber ABS/TCS warning indicators turn on.

Conditions for Clearing the DTC

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

•	100 drive cycles pass with no DTC 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 or Scan Tool Diagnostics located in this section 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 of 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:

Add two teaspoons of salt to twelve ounces of water to make a five percent saltwater solution.
Spray the suspected area with the 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, inspect the suspected circuits.

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

•	Corrosion and/or water intrusion of terminals.

Important: Difficulty may occur when trying to locate the 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.

Front Wheel Speed Sensor Resistance

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

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.

Important: Zero the J 39200 test leads before making any resistance measurements.

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

Step

Action

Value(s)

Yes

Was the Diagnostic System Check performed?

Go to Step 2

Go to Diagnostic System Check - ABS

Turn the ignition switch to the OFF position.
Inspect the left front wheel speed sensor and the left front wheel speed sensor harness connector for physical damage.

Is there any physical damage?

Go to Step 23

Go to Step 3

Inspect the following components for physical damage:

•	The left front wheel speed sensor jumper harness

•	The left front wheel speed sensor jumper harness connectors

Is there any physical damage?

Go to Step 22

Go to Step 4

Disconnect the left front wheel speed sensor directly at the left front wheel speed sensor connector.
Use the J 39200 in order to measure the resistance between the left front wheel speed sensor connector terminal A and the left front wheel speed sensor connector terminal B.

Is the resistance within the specified range?

1020-1137 ohms at 20°C (68°F)

Go to Step 5

Go to Step 23

Select the A/C VOLTAGE scale on the J 39200 .
Spin the left front wheel by hand while observing the voltage reading on the J 39200 .

Is the voltage equal to or greater than the specified voltage?

100 mV

Go to Step 6

Go to Step 23

Disconnect the 24-way EBCM/EBTCM connector C1.
Use the J 39200 in order to measure the resistance between the 24-way EBCM/EBTCM connector C1 terminal A5 and the 24-way EBCM/EBTCM connector C1 terminal B4.

Is continuity present between the 24-way EBCM/EBTCM connector C1 terminal A5 and terminal B4?

Go to Step 8

Go to Step 7

Inspect the 24-way EBCM/EBTCM connector C1 for the following conditions:

•

Damage

•	Poor terminal contact

•	Terminal corrosion

•	(Damage, poor terminal contact, and terminal corrosion may cause a short between the 24-way EBCM/EBTCM connector C1 terminal A5 and the EBCM/EBTCM connector C1 terminal B4.

Inspect the remaining terminals of the 24-way EBCM/EBTCM connector C1 for the following conditions:

•

Damage

•	Poor terminal contact

•	Terminal corrosion

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

Go to Step 21

Go to Step 9

Repair the short between CKT 873 and CKT 830.

Is the repair complete?

Go to Diagnostic System Check - ABS

Use the J 39200 in order to measure the resistance between the 24-way EBCM/EBTCM connector C1 terminal A5 and ground.

Is continuity present between the 24-way EBCM/EBTCM connector C1 terminal A5 and ground?

Go to Step 10

Go to Step 11

Repair the short to ground in CKT 830.

Is the repair complete?

Go to Diagnostic System Check - ABS

Use the J 39200 in order to measure the resistance between the 24-way EBCM/EBTCM connector C1 terminal B4 and ground.

Is continuity present between the 24-way EBCM/EBTCM connector C1 terminal B4 and ground?

Go to Step 12

Go to Step 13

Repair the short to ground in CKT 837.

Is the repair complete?

Go to Diagnostic System Check - ABS

Use the J 39200 in order to measure the resistance between the 24-way EBCM/EBTCM connector C1 terminal A5 and the wheel speed sensor connector terminal A.

Is continuity present in CKT 830 between the 24-way EBCM/EBTCM connector C1 terminal A5 and the wheel speed sensor connector terminal A?

Go to Step 15

Go to Step 14

Repair the open or high resistance in CKT 830.

Is the repair complete?

Go to Diagnostic System Check - ABS

Use the J 39200 in order to measure the resistance between the 24-way EBCM/EBTCM connector C1 terminal B4 and the wheel speed sensor connector terminal B.

Is continuity present in CKT 873 between the 24-way EBCM/EBTCM connector C1 terminal B4 and the wheel speed sensor connector terminal B?

Go to Step 17

Go to Step 16

Repair the open or high resistance in CKT 873.

Is the repair complete?

Go to Diagnostic System Check - ABS

Reconnect the 24-way EBCM/EBTCM harness connector C1.
Reconnect the left front wheel speed sensor harness connector.
Install a scan tool.
Test drive the vehicle at a speed above 24 km/h (15 mph) for at least 30 seconds.
Use the scan tool in order to read the DTCs.

Does DTC C1221 set as a current DTC?

Go to Step 18

Go to Step 20

Select Data List on the scan tool.
Monitor the wheel speed sensor speeds.
Drive the vehicle in the following manner:

-	Slowly accelerate to 65 km/h (40 mph).

-	Slowly decelerate to 0 km/h (0 mph).

Is the speed of the left front wheel speed sensor constantly higher than the speed of the three remaining wheel speed sensors?

Go to Step 23

Go to Step 19

Replace the EBCM/EBTCM. Refer to Electronic Brake and Traction Control Module Replacement .

Is the repair complete?

Go to Diagnostic System Check - ABS

Is the malfunction intermittent or not present at this time?

Go to Diagnostic Aids

Go to Diagnostic System Check - ABS

Replace all of the terminals that exhibit signs of poor terminal contact, corrosion, or damaged terminals.

Is the repair complete?

Go to Diagnostic System Check - ABS

Replace the left front wheel speed sensor jumper harness. Refer to Wheel Speed Sensor Jumper Harness Replacement .

Is the repair complete?

Go to Diagnostic System Check - ABS

Replace the left front wheel speed sensor. Refer to Wheel Speed Sensor Replacement .

Is the repair complete?

Go to Diagnostic System Check - ABS