GM Service Manual Online
For 1990-2009 cars only

Object Number: 247742  Size: MF
ABS Components
Antilock Brake System Schematics
Handling ESD Sensitive Parts Notice

Circuit Description

DTC 1263 identifies an ABS motor circuit that is shorted shorts to voltage or an ABS motor that has low or no resistance. The malfunction will cause one of the following conditions to occur:

    • The ABS motor will not be controlled at the commanded current rate.
    • The ABS motor will turn in the opposite direction or not at all.

Conditions for Setting the DTC

DTC C1263 can set only when the ABS motor is commanded off.

A malfunction exists if The EBCM/EBCTM detects an out of range voltage on either of the right front ABS motor circuits.

An out of range voltage on either circuit indicates one of the following conditions:

    • A circuit shorts to voltage.
    • An ABS brake motor shorts internally.

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

Use the Scan Tool Manual Control function in order to exercise ABS motor movement of affected channel in both directions while applying light pressure on the brake pedal.

An intermittent malfunction may be indicated if erratic or jumpy brake pedal movement is detected while performing an apply or release function of the ABS monitor.

The following conditions may cause an intermittent malfunction:

    • A poor connection
    • Rubbed-through wire insulation
    • A broken wire inside the insulation

If the malfunction is not current, use the following procedure to pinpoint an intermittent malfunction in the motor circuitry or connections:

  1. Wiggle the wires of the affected channel.
  2. Inspect if the DTC resets.

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.

Thoroughly inspect any circuitry that may cause 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

Clear the DTCs after completing the diagnosis. Test drive the vehicle for three drive cycles in order to verify that the DTC does not reset. Use the following procedure in order to complete one drive cycle:

  1. Start the vehicle.
  2. Drive the vehicle over 16 km/h (10 mph).
  3. Stop the vehicle.
  4. Turn the ignition to the OFF position.

Important: Zero the J 39200 test leads before making any resistance measurements. Refer to the J 39200 user's manual.

Step

Action

Value(s)

Yes

No

1

Was the Diagnostic System Check performed?

--

Go to Step 2

Go to Diagnostic System Check

2

Does DTC C1263 occur intermittently?

--

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn the ignition switch to the OFF position.
  2. Disconnect the 6-way ABS brake motor pack connector.
  3. Disconnect the 8-way EBCM/EBTCM connector C2
  4. Turn the ignition switch to the RUN position.
  5. Do not start the engine.

  6. Use the J 39200 in order to measure the voltage between the 6-way ABS brake motor pack harness connector terminal B and ground.

Is the voltage within the specified range?

0-1 V

Go to Step 4

Go to Step 10

4

Use the J 39200 in order to measure the voltage between the 6-way ABS brake motor pack harness connector terminal A and ground.

Is the voltage within the specified range?

0-1 V

Go to Step 5

Go to Step 11

5

  1. Turn the ignition switch to the OFF position.
  2. Use the J 39200 in order to measure the resistance between the 6-way ABS motor pack harness connector terminal B and the 6-way ABS motor pack harness connector terminal A.

Is the resistance within the specified range?

OL

(Infinite)

Go to Step 6

Go to Step 12

6

Use the J 39200 in order to measure the resistance between the 6-way ABS motor pack connector terminal B and the 6-way ABS motor pack connector terminal A.

Is the resistance measured equal to or greater than the specified range?

0.2 ohms

Go to Step 7

Go to Step 9

7

  1. Inspect the following components for damage:
  2. • The 6-way ABS motor pack connector
    •  The 6-way ABS motor pack harness connector
    • Damage may cause a short to voltage with the connector connected.
  3. Inspect the following components for damage:
  4. • The 8-way EBCM/EBTCM connector C2
    • The 8-way EBCM/EBTCM harness connector C2
    • Damage may cause a short to voltage with the connector connected.
  5. Inspect CKT 1282 and CKT 1283 for signs of damage.
  6. Damage may cause a short to voltage.

Is there damage which may cause a short to voltage?

--

Go to Step 13

Go to Step 8

8

  1. Reconnect the 6-way ABS motor pack connector.
  2. Reconnect the 8-way EBCM/EBTCM connector C2.
  3. Test drive the vehicle at a speed of at least 16 km/h (10 mph).
  4. Turn the ignition switch to the OFF position.
  5. Repeat the drive sequence two additional times.
  6. Use the Scan Tool in order to inspect for DTCs.

Did DTC C1263 set as a current DTC during the last three drive cycles?

--

Go to Step 14

Go to Step 15

9

Replace the ABS motor pack.

Is the repair complete?

--

Go to Diagnostic System Check

--

10

Repair the short to voltage in CKT 1282.

Is the repair complete?

--

Go to Diagnostic System Check

--

11

Repair the short to voltage in CKT 1283.

Is the repair complete?

--

Go to Diagnostic System Check

--

12

Repair the short between CKT 1282 and CKT 1283.

Is the repair complete?

--

Go to Diagnostic System Check

--

13

Replace all of the following components that are damaged:

    • The terminals
    • The connectors
    • The wires
        Damage may cause a short to voltage.

Is the repair complete?

--

Go to Diagnostic System Check

--

14

Replace the EBCM/EBTCM.

Is the repair complete?

--

Go to Diagnostic System Check

--

15

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

Is the repair complete?

--

Go to Diagnostic Aids

--