Checking connectors and bus wire
Remember that the CAN network is only a communications network. There are therefore no fuses, switches and sensors on the CAN bus. Check the resistance as described below (see references).
To maintain the correct values the battery should be disconnected when measuring resistance.
Check the bus wire for a short circuit to voltage supply as described in Short-circuit to supply voltage, intermittent faults and for an intermittent open circuit as described in Open-circuit, intermittent faults .
HINT: When checking for an open circuit, check if possible from the rear of the connector concerned so that it is not damaged.
Also check the intermediate connectors for contact resistance and oxidation as described in Contact resistance and oxidation and for a loose contact as described in Loose connections (terminals) .
HINT: If the fault is found before all the wires below have been checked trouble-shooting is not necessary on the wires.
The following wires and connectors should be checked to locate the short circuit.
Wire between:
- electronic throttle module (ETM) 4 and engine control module (ECM) 55A.
To connect the test box to the ETM control unit, see Connecting the breakout box
To connect the test box to the ECM control unit, see Connecting the breakout box
- engine control module (ECM) 1B and transmission control module (TCM) 1B.
To connect the test box to the ECM control unit, see Connecting the breakout box
To connect the test box to the TCM control unit, see Connecting breakout box, Transmission control module (TCM) (AW) or Connecting the breakout box (GM).
- transmission control module (TCM) 2B and anti-lock braking system (ABS) 10 (or 20 if the vehicle has a switch button with the text "DSTC" on the center console).
To connect the test box to the TCM control unit, see Connecting breakout box, Transmission control module (TCM) (AW) or Connecting the breakout box (GM).
To connect the test box to the ABS control unit, see Connecting the ABS breakout box
- engine control module (ECM) 1B and anti-lock braking system (ABS) 10 (or 20 if the vehicle has a switch button with the text "DSTC" on the center console).
To connect the test box to the ECM control unit, see Connecting the breakout box
To connect the test box to the ABS control unit, see Connecting the ABS breakout box
- central electronic module (CEM) 18B and anti-lock braking system (ABS) 10 (or 20 if the vehicle has a switch button with the text "DSTC" on the center console.) Also check intermediate connector 54/3R.
To connect the test box to the CEM control unit, see Connecting the breakout box
To connect the test box to the ABS control unit, see Connecting the ABS breakout box
Applies to automatic gear box.
Applies to automatic gear box.
Applies to manual gear box.
Additional information:
- The voltage should be between approximately 1.5 V and 2.5 V.
- To disconnect the battery, see Battery, disconnecting