GM Service Manual Online
For 1990-2009 cars only

Object Number: 393824  Size: MF
ABS Components
Antilock Brake System Schematics
Handling Electrostatic Discharge Sensitive Parts Notice

Circuit Description

The speed sensor used on this vehicle is a multiple pole magnetic pickup. This sensor produces an AC signal that the EBCM/EBTCM uses the frequency from to calculate the wheel speed.

Conditions for Setting the DTC

The DTC can be set when the brake is off and no wheel speed DTCs (DTC C1232 through C1235) are present.

This DTC will set anytime the EBCM sees a wheel speed variation of more than 24 Km/h (15 mph) in 0.01 seconds. The 14 Km/h  (15 mph) change must occur 5 times with less than 1.00 seconds between each occurrence for a code to be set.

Action Taken When the DTC Sets

    • A malfunction DTC stores.
    • The ABS/TCS disables.
    • The ABS/TCS indicator(s) turn on.

Conditions for Clearing the DTC

    • Condition for DTC is no longer present and scan tool clear DTC function is used.
    • 100 ignition cycles have passed with no DTC(s) detected.

Diagnostic Aids

    • It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect wiring and connectors may result in misdiagnosis, causing part replacement with reappearance of the malfunction.
    • An intermittent malfunction can be caused by poor connections, broken insulation, or a wire that is broken inside the insulation.
    • If an intermittent malfunction exists refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.

DTC C1228 RR Excessive Wheel Speed Variation

Step

Action

Value(s)

Yes

No

1

Was the Diagnostic System Check performed?

--

Go to Step 2

Go to Diagnostic System Check - ABS

2

Did DTC C1235 set as a current or history DTC?

--

Go to DTC C1235 RR Wheel Speed Circuit Open or Shorted DTC C1291 Open Brake Lamp Switch Contacts During Deceleration or DTC C1293 Code C1291 Set in Previous Ignition Cycle

Go to Step 3

3

  1. Inspect the WSS wiring and connectors for damage.
  2. Inspect WSS for looseness or damage.

Is physical damage of sensor evident?

--

Go to Step 4

Go to Step 5

4

Replace wheel speed sensor. Refer to Wheel Speed Sensor Replacement .

Is the repair complete?

--

Go to Step 11

--

5

Inspect the WSS jumper harness for physical damage.

Is physical damage to the jumper harness evident?

--

Go to Step 6

Go to Step 7

6

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

Is the repair comnplete?

--

Go to Step 11

--

7

  1. Disconnect the WSS at the sensor pigtail.
  2. Using J 39200 DMM, measure the resistance between terminals A and B of the WSS.

Is the resistance within the range specified in the value(s) column?

850-1350ohms

Go to Step 8

Go to Step 4

8

  1. With J 39200 DMM still connected, select the mV AC scale.
  2. Spin the wheel at approximately 1 revolution per second by hand while monitoring the AC output.
  3. While monitoring the AC output notice if the reading on the J 39200 DMM goes below 100 mV.

Does the AC voltage fall below the specified value?

100 mV

Go to Step 4

Go to Step 9

9

  1. Disconnect the EBCM/EBTCM harness connector.
  2. Install the J 39700 Universal Pinout Box using the J 39700-99 Cable Adapter to the EBCM/EBTCM harness connector only.
  3. Using a DMM, measure for continuity between terminals A5 and A6 of the Universal Pinout Box.

Is there continuity between terminals A5 and A6 of the Universal Pinout Box?

--

Go to Step 10

Go to Step 11

10

Repair the short between CKT(s) 882 and 883. (If a short is found in the jumper harness, replace the jumper harness assembly.)

Is the repair complete?

--

Go to Step 11

--

11

  1. Reconnect all connectors.
  2. Using a scan tool, clear the DTC.
  3. Carefully test drive vehicle above 24 Km/h (15 mph) for at least 30 seconds while monitoring a scan tool.

Does DTC reset as a current DTC?

--

Go to Step 12

System OK

12

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

Is the replacement complete?

--

Go to Diagnostic System Check - ABS

--