Signal Too Low. Intermittent Fault

Signal too low. Intermittent fault

Checking connectors and bus wire

Note! 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).

Note! To maintain the correct values the battery should be disconnected when measuring resistance.

Check the bus wire for a short circuit to ground as described in Checking wiring and terminals. Intermittent faults Checking Wiring and Terminals. Intermittent Faults.
Also check the intermediate connectors for contact resistance and oxidation as described in Checking wiring and terminals. Intermittent faults Checking Wiring and Terminals. Intermittent Faults and for a loose contact as described in Checking wiring and terminals. Intermittent faults Checking Wiring and Terminals. Intermittent Faults.

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
electronic throttle module (ETM) 3 and engine control module (ECM) 37A.
To connect the test box to the ETM control unit, see Connecting the breakout box, B5244T5, B5254T2 Connecting the Breakout Box
To connect the test box to the ECM control unit, see Connecting the breakout box, B5244T5, B5254T2 Connecting the Breakout Box
Note! Applies to automatic gear box.

engine control module (ECM) 1B and transmission control module (TCM) 1B.
engine control module (ECM) 13B and transmission control module (TCM) 13B.
To connect the test box to the ECM control unit, see Connecting the breakout box, B5244T5, B5254T2 Connecting the Breakout Box
To connect the test box to the TCM control unit, see Connecting breakout box, Transmission control module (TCM) Connecting Breakout Box, Transmission Control Module (TCM) (AW) or (GM).
Note! Applies to automatic gear box.

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 centre console).
transmission control module (TCM) 14B and anti-lock braking system (ABS) 11 (or 19 if the vehicle has a switch button with the text "DSTC" on the centre console).
To connect the test box to the TCM control unit, see Connecting breakout box, Transmission control module (TCM) Connecting Breakout Box, Transmission Control Module (TCM) (AW) or (GM).
To connect the test box to the ABS control unit, see Connecting the ABS breakout box Pinout Values and Diagnostic Parameters
Note! Applies to manual gear 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 centre console).
engine control module (ECM) 13B and anti-lock braking system (ABS) 11 (or 19 if the vehicle has a switch button with the text "DSTC" on the centre console).
To connect the test box to the ECM control unit, see Connecting the breakout box, B5244T5, B5254T2 Connecting the Breakout Box
To connect the test box to the ABS control unit, see Connecting the ABS breakout box Pinout Values and Diagnostic Parameters
- 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 centre console.) Also check intermediate connector 54/3R.
central electronic module (CEM) 17B and anti-lock braking system (ABS) 11 (or 19 if the vehicle has a switch button with the text "DSTC" on the centre console.) Also check intermediate connector 54/3R.
To connect the test box to the CEM control unit, see Connecting the breakout box Connecting the Breakout Box, Central Electronic Module (CEM)
To connect the test box to the ABS control unit, see Connecting the ABS breakout box Pinout Values and Diagnostic Parameters

Additional information:
- The voltage should be between approximately 1.5 V and 2.5 V.
- For wiring diagram for bus wire and for position of connectors see Service Handbook, Section 3, Wiring Diagram.
- To disconnect the battery, see Battery, disconnecting Battery Disconnecting









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