For 1990-2009 cars
ABS Components
Cell 44: ABS/TCS Switch, UART, PCM, and Traction Control Switch
Handling ESD Sensitive Parts Notice
Cell 50: UART Serial Data Line

### Circuit Description

The serial data UART allows information to be exchanged from module to module as needed. This is done by the PCM. The PCM requests and sends all of the information that is transmitted via serial data UART. When the scan tool is connected to the serial data UART, the scan tool takes over for the PCM and sends and requests the needed information.

### 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.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
DEFINITION: The scan tool will not communicate with the EBCM/EBTCM.
1 | Did you perform the ABS Diagnostic System Check? | -- | Go to Step 2 | Go to Diagnostic System Check - ABS
2 | Turn the ignition switch to the RUN position with the engine off. May the scan tool communicate with other modules on the UART serial data line, such as the PCM? | -- | Go to Step 3 | Go to Data Link Communications System Check in Data Link Communications
3 | Inspect the ABS/CCR Fuse in the IP fuse block. Is the fuse OK? | -- | Go to Step 4 | Go to Step 8
4 | Inspect the ABS SOL Fuse in the LH underhood fuse block. Is the fuse OK? | -- | Go to Step 10 | Go to Step 5
5 |

1. Turn OFF the ignition.
2. Remove the ABS SOL Fuse.
3. Disconnect the EBCM/EBTCM connector.
4. Connect the J 39700 using the J 39700-25 cable adapter to the EBCM/EBTCM harness connector only.
5. Use the J 39200 DMM in order to measure the resistance between terminal D and terminal B of the J 39700 .

Is the resistance within the specified range?

OL (infinite)

Go to Step 6

Go to Step 7

6 | Replace the EBCM/EBTCM. Refer to Electronic Brake Control Module Replacement . Did you complete the repair? | -- | Go to Diagnostic System Check - ABS | --
7 | Repair a short to ground CKT 342 (RED). Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Diagnostic System Check - ABS | --
8 |

1. Turn OFF the ignition.
2. Remove the ABS/CCR Fuse.
3. Disconnect the EBCM/EBTCM connector.
4. Connect the J 39700 using the J 39700-25 cable adapter to the EBCM/EBTCM harness connector only.
5. Use J 39200 DMM in order to measure the resistance between terminal A and terminal B of the J 39700 .

Is the resistance within the specified range?

OL (infinite)

Go to Step 6

Go to Step 9

9 | Repair a short to ground CKT 641 (BRN). Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Diagnostic System Check - ABS | --
10 |

1. Install the fuses if removed.
2. Turn ON the ignition leaving the engine OFF.
3. Use the J 39200 DMM in order to measure the voltage at the ABS/CCR Fuse by probing between the fuse test terminals and a good ground.

Is the voltage within the specified range?

Battery Voltage

Go to Step 11

Go to Wiring Repairs in Wiring Systems

11 | Use the J 39200 DMM in order measure the voltage at the ABS SOL Fuse by probing between the fuse test terminals and a good ground. Is the voltage within the specified range? | Battery Voltage | Go to Step 12 | Go to Wiring Repairs in Wiring Systems
12 |

1. Turn OFF the ignition.
2. Disconnect the EBCM/EBTCM connector.
3. Connect the J 39700 universal pinout box using the J 39700-25 cable adapter to the EBCM/EBTCM harness connector only.
4. Use the J 39200 DMM in order to measure the resistance between the J 39700 terminal B and a good ground.

Is the resistance less than the specified value?

2 ohms

Go to Step 14

Go to Step 13

13 | Repair an open or high resistance in CKT 1050 (BLK) or G106. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Diagnostic System Check - ABS | --
14 |

1. Turn ON the ignition leaving the engine OFF.
2. Use the J 39200 DMM in order to measure the voltage between the J 39700 terminal A and terminal B.

Is the voltage within the specified range?

Battery Voltage

Go to Step 16

Go to Step 15

15 | Repair an open in CKT 641 (BRN). Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Diagnostic System Check - ABS | --
16 | Use the J 39200 DMM in order to measure the voltage between the J 39700 terminal D and terminal B. Is the voltage within the specified range? | Battery Voltage | Go to Step 6 | Go to Step 17
17 | Repair an open in CKT 342 (RED). Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Diagnostic System Check - ABS | --