Short to B+ in CAN Bus Line

CAN COMMUNICATION SYSTEM: Short to B+ in CAN Bus Line

Short to B+ in CAN Bus Line

DESCRIPTION

A short to B+ is suspected in the CAN bus line when the resistance between terminals 6 (CANH) and 16 (BAT), or terminals 14 (CANL) and 16 (BAT) of the DLC3 is below 1 MOhms.

WIRING DIAGRAM

INSPECTION PROCEDURE

PROCEDURE

1. CHECK FOR SHORT TO B+ IN CAN BUS WIRE
(a) Turn the engine switch off.

(b) Disconnect the DLC3 branch line connector (J8) from the CAN LH J/C B side (without earth terminal).
- Before disconnecting the connector, make a note of where it is connected.
- Reconnect the connector to its original position.

NG -- REPAIR OR REPLACE DLC3 BRANCH WIRE OR CONNECTOR
OK -- Continue to next step.
2. RECONNECT CONNECTOR
(a) Reconnect the DLC3 branch line connector (J8) to the CAN LH J/C B side (without earth terminal).
NEXT -- Continue to next step.
3. CHECK FOR SHORT TO B+ IN CAN BUS WIRE

(a) Disconnect connectors from the CAN LH J/C or CAN RH J/C one at a time.
HINT: Disconnect the ECU and sensor connectors other than the DLC3 branch lines and CAN main bus lines between the CAN LH J/C and CAN RH J/C.
(b) Using an ohmmeter, measure the resistance between terminals 6 (CANH) and 16 (BAT), and between terminals 14 (CANL) and 16 (BAT) of the DLC3 each time a connector is disconnected.

Wiring color:

NOTE: Do not reconnect the disconnected connectors until this inspection is complete because there may be a short to B+ in 2 or more CAN bus lines.

Result:

(c) When there is a short to B+ in one or more of the bus lines that connect to an ECU (or sensor):
(1) Reconnect all of the connectors to the CAN J/C, except for the one that was disconnected last (the bus line that is shorted to B+). Check that the resistance shown on the tester is normal (1 MOhms or more) to confirm that there is a short to B+ in the one bus line only.
HINT:
- The connectors connected to the CAN J/C can be distinguished according to the color of the communication bus lines and the shape of the connectors.
- Reconnecting the connectors to non-specified positions on the CAN J/C does not affect system operation. However, it is preferred to reconnect the connectors to their specified positions to avoid negative effects on the wiring such as tension on the wiring harnesses, and to make future maintenance easier.

A -- REPAIR OR REPLACE CAN BUS MAIN WIRE (CAN LH J/C - CAN RH J/C)
B -- Continue to next step.
4. RECONNECT CONNECTOR
(a) Reconnect the connector of the bus line that is shorted to B+ to the CAN J/C (the connector that caused the bus line resistance to change to 1 MOhms or more when it was disconnected).
NEXT -- Continue to next step.
5. CHECK FOR SHORT TO B+ IN CAN BUS WIRE

(a) Disconnect the connector that includes terminals CANH and CANL from the ECU (or sensor) to which the bus line shorted to B+ is connected. CAN Communication System

(b) Measure the resistance according to the value(s) in the table below.
Standard resistance:

HINT: If the resistance changes to 1 MOhms or higher when the connector is disconnected from the ECU (or sensor), there may be a short in the ECU (or sensor).

NG -- REPAIR OR REPLACE CORRESPONDING ECU OR SENSOR BUS LINE OR CONNECTOR
OK -- REPLACE CORRESPONDING ECU OR SENSOR