For 1990-2009 cars
ABS Components
Cell 44: PWR, GND, ABS Relays
Cell 10: IGN 1 Fuse, Ignition Switch
Cell 10: Battery Power
Cell 10: IGN 3 Fuse and Ignition Switch (Buick)
Cell 10: IGN 3 Fuse, Ignition Switch (Oldsmobile)
Cell 10: CHIME (IGN 1) Fuse (Buick)
Cell 10: CHIME (IGN 1) Fuse (Oldsmobile)
Cell 10: ABS PUMP MOTOR, ABS MAIN, and COOLING FAN Fuses
Cell 14: G202 (1 of 3) (Buick)
Cell 14: G202 (1 of 3) (Oldsmobile)
Cell 14: G102, G104, G106, G110 and G301
Cell 50: UART Serial Data Line

### Circuit Description

When the ignition switch is first turned to the RUN position, the EBCM/EBTCM goes through a self-test lasting 2-4 seconds. During this test, the EBCM/EBTCM grounds terminal 52, causing the amber ANTILOCK indicator to light. This serves as an indicator bulb test. The EBCM/EBTCM also grounds terminal 34, energizing the main relay. This removes the indicator ground path provided through the antilock diode and the main relay contacts.

When the self-test is completed (and no faults detected) the EBCM/EBTCM removes the ground at terminal 52, turning OFF the indicator. The main relay remains energized.

When the EBCM/EBTCM detects a malfunction, it grounds terminal 52 causing the amber ANTILOCK indicator to light. (Note: The EBCM/EBTCM also de-energizes the main relay creating a redundant ground path.)

When the EBCM/EBTCM is disabled for any reason (i.e., open ABS fuse), the main relay is de-energized. This provides an ANTILOCK indicator ground path through the antilock diode and main relay contacts, and causes the indicator to come ON with no DTC being set.

### Diagnostic Aids

Possible causes:

• | Open in CKT 1451, 852, 39, 351, or 1633.

• | Open IGN 1 fuse (Buick) or CADME Fuse (Oldsmobile).

• | Open bulb.

• | Short to voltage in CKT 852.

• | Open or shorted antilock diode.

• | Main relay fails "engaged."

• | Short to ground in CKT 39, 852, or 1632.

#### ABS Indicator Inoperative with No DTC(s) Set

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Diagnostic System Check performed? | -- | Go to Step 2 | Go to Diagnostic System Check
2 |

1. Turn the ignition switch to the OFF position.
2. Disconnect EBCM/EBTCM connector.
3. Connect J 38716 pinout box.
4. Using J 38716 set to ohms, measure resistance between J 38716 terminal 1 and ground.

Is the resistance less than the specified value?

2 ohms

Go to Step 3

Go to Step 11

3 |

1. Disconnect the ABS main relay.
2. Turn the ignition switch to the RUN position.
3. Using J 39200, measure voltage between J 38716 terminals 52 and 1.

Is the voltage within the specified range?

Battery Voltage

Go to Step 4

Go to Step 12

4 |

1. Turn the ignition switch to the RUN position.
2. Connect a fused jumper between J 38716 pinout box terminals 52 and 1.

Does the ANTILOCK indicator illuminate?

--

Go to Step 5

Go to Step 17

5 |

1. Turn the ignition switch to the OFF position.
2. Using J 39200 and the J 38716 terminals 3 and 52, check the antilock diode. Verify proper diode polarity.

Does diode check OK?

--

Go to Step 6

Go to Step 18

6 |

1. Disconnect J 38716.
2. Reinstall the ABS main relay and reconnect all connectors.
3. Turn the ignition switch to the RUN position.

Does the ANTILOCK indicator illuminate for 2-4 seconds and then go out?

--

Go to Diagnostic System Check

Go to Step 7

7 |

1. Turn the ignition switch to the OFF position.
2. Disconnect the ABS main relay.
3. Using the J 39200 set to ohms, measure resistance between main relay terminals 30 and 87A.

Is the resistance less than the specified range?

2 ohms

Go to Step 8

Go to Step 19

8 |

1. Remove the ABS fuse of IP fuse block.
2. Turn the ignition switch to the RUN position.
3. Using J 39200 set to DC scale, measure voltage between the main relay harness connector terminal 30 and ground.

Is the voltage within the specified range?

Battery Voltage

Go to Step 9

Go to Step 20

9 | Measure the voltage between the ABS main relay harness connector terminals 30 and 87A. Is the voltage within the specified range? | Battery Voltage | Go to Step 10 | Go to Step 21
10 |

1. Turn the ignition switch to the OFF position.
2. Disconnect the EBCM/EBTCM connector.
3. Using the J 39200 set to ohms, measure resistance between the ABS main relay harness connector terminal 85 and ground.

Is the resistance less than the specified value?

2 ohms

Go to Step 22

Go to Step 23

11 | Repair the open or high resistance in CKT 1451. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | --
12 |

1. Turn the ignition switch to the OFF position.
2. Check the IP fuse block IGN1 fuse (Buick) or CHIME (Oldsmobile).

Is the fuse open?

--

Go to Step 13

Go to Step 14

13 | Repair the short to ground in CKT 39. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | --
14 | Remove and check the ANTILOCK indicator bulb. Is the bulb open? | -- | Go to Step 15 | Go to Step 16
15 | Replace the ANTILOCK indicator bulb. Is the repair complete? | -- | Go to Diagnostic System Check | --
16 | Repair the open or high resistance in CKT 39 or CKT 852. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | --
17 |

1. Repair the short to voltage in CKT 852. Refer to Wiring Repairs in Wiring Systems.
2. Check antilock diode and main relay for possible damage.

Is the repair complete?

--

Go to Diagnostic System Check

--

18 | Replace antilock diode. Observe the polarity. Refer to Antilock Diode Replacement . Is the repair complete? | -- | Go to Diagnostic System Check | --
19 | Replace the ABS main relay. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | --
20 | Repair the open or high resistance in CKT 1633. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | --
21 | Repair the open or high resistance in CKT 351. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | --
22 | Repair the short to ground in CKT 1632. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | --
23 |

1. Replace or repair the wiring harness connector as needed to obtain proper connector retention.
2. Clear DTCs.
3. Verify proper operation.

Does the system operate properly?

--

Go to Diagnostic System Check

Go to Step 24

24 | Replace the EBCM/EBTCM. Refer to Electronic Brake and Traction Control Module Replacement . Is the repair complete? | -- | Go to Diagnostic System Check | --