Two-Wire Bus System, Checking

Two-wire bus system, checking - 5 Spd. Automatic Transmission 01V

If the DTC table indicates to check the bus:

- Use the applicable wiring diagram, determine how many control modules communicate with each other via the bus.
- Press the -0- button twice to select the function "Automatic test sequence".
- Before checking the bus wires, make sure that none of the control modules connected are malfunctioning.

A malfunction will disrupt communication to other control modules.

Is there a malfunction?

- Fix the malfunction before proceeding.
- Note malfunction and erase DTC memory of all control modules.
- Press buttons -0- and -6- to select "End Output" function 06. Press -Q- button to confirm input.
- End output of scan tool by selecting the function "end output".

When necessary repairs have been made:

- Check bus wires if communication to the control modules is still faulty. If yes, check bus wires.

There can be two situations:

^ Two control modules communicate via a "two-line bus system"
^ Three or more control modules communicate via a "two-line bus system"

Two control modules communicate via a "two-line bus system"

- Switch ignition off.





- Disconnect both control modules.
- Check bus wires for open circuit.





- Check whether there is a short circuit between bus wires.





- Check bus wires for short circuit to B+ or Ground (GND).

If there are no malfunctions in the bus wires:

- As a test, replace one of the control modules. Select a control module that will take the least amount of time to replace and cost the least amount of money.
- If communication between the control modules across the bus is still interrupted, replace the second control module.

Three or more control modules are communicating across a "two-line bus system"

- Analyze DTCs stored in the memories of the control modules.





Example 1:

From the DTCs stored in the memories, determined that control module 1 is not communicating with control modules 2 and 3.





- Switch ignition off.
- Disconnect the control modules connected across the bus wires and check bus wires for open circuit.
- Replace control module 1 if bus wires are OK.





Example 2:

From the DTCs stored in the memories, determined that control module 2 is not communicating with control modules 1 and 3.





- Switch ignition off.
- Disconnect the control modules connected across the bus wires and check bus wires for open circuit.
- Replace control module 2 if bus wires are OK.

Example 3:

Using DTCs stored in the memories, determined that none of the control modules are sending or receiving signals.





- Switch ignition off.





- Disconnect the control modules connected across the bus wires and check for a short circuit between the bus wires.





- Check bus wires for short circuit to B+ or Ground (GND).
- If there are no malfunctions found in the bus wires, check whether one of the control modules is responsible for a short circuit of the bus wires to each other, to B+ or to Ground (GND).

Disconnect each of the control modules connected via the bus wires one at a time and check whether the malfunction "Hardware faulty" has been eliminated.

If it was eliminated, replace the control module that is currently disconnected. If malfunction was not eliminated, re-connect that control module and disconnect the next control module connected via the bus wires.