Lexus ES: Check Bus 3 Line for Short to GND
DESCRIPTION
There may be a short circuit between one of the CAN bus lines and GND when there is no resistance between terminal 6 (CA3H) of the central gateway ECU (network gateway ECU) and terminal 4 (CG) of the DLC3, or terminal 21 (CA3L) of the central gateway ECU (network gateway ECU) and terminal 4 (CG) of the DLC3.
| Symptom | Trouble Area |
|---|---|
| There is no resistance between terminal 6 (CA3H) of the central gateway ECU (network gateway ECU) and terminal 4 (CG) of the DLC3, or terminal 21 (CA3L) of the central gateway ECU (network gateway ECU) and terminal 4 (CG) of the DLC3. |
|
WIRING DIAGRAM
CAUTION / NOTICE / HINT
CAUTION:
When performing the confirmation driving pattern, obey all speed limits and traffic laws.
NOTICE:
-
Because the order of diagnosis is important to allow correct diagnosis, make sure to begin troubleshooting using How to Proceed with Troubleshooting when CAN communication system related DTCs are output.
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- Before measuring the resistance of the CAN bus, turn the engine switch off and leave the vehicle for 1 minute or more without operating the key or any switches, or opening or closing the doors. After that, disconnect the cable from the negative (-) battery terminal and leave the vehicle for 1 minute or more before measuring the resistance.
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After turning the engine switch off, waiting time may be required before disconnecting the cable from the negative (-) battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) battery terminal notices before proceeding with work.
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After performing repairs, perform the DTC check procedure and confirm that the DTCs are not output again.
DTC check procedure: Turn the engine switch on (IG) and wait for 1 minute or more. Then operate the suspected malfunctioning system and drive the vehicle at 60 km/h (37 mph) or more for 5 minutes or more.
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After the repair, perform the CAN bus check and check that all the ECUs and sensors connected to the CAN communication system are displayed as normal.
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Before replacing the DCM (telematics transceiver), refer to Registration.
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HINT:
- Before disconnecting related connectors for inspection, push in on each connector body to check that the connector is not loose or disconnected.
- When a connector is disconnected, check that the terminals and connector body are not cracked, deformed or corroded.
PROCEDURE
| 1. | CHECK FOR SHORT TO GND IN CAN BUS LINE (NO. 4 CAN JUNCTION CONNECTOR) |
(a) Disconnect the cable from the negative (-) battery terminal.
(b) Disconnect the G98 No. 4 CAN junction connector.
(c) Measure the resistance according to the value(s) in the table below.
| *1 | DLC3 | - | - |
| *a | Front view of wire harness connector (to No. 4 CAN Junction Connector) | *b | to DCM (Telematics Transceiver) (w/ Telematics Transceiver) |
| *c | to Central Gateway ECU (Network Gateway ECU) | *d | to Option Connector (Bus Buffer ECU) (w/ CAN Compatible Optional Devices) |
Standard Resistance:
| Tester Connection | Condition | Specified Condition | Connected to |
|---|---|---|---|
| G98-8 (CANH) - G57-4 (CG) | Cable disconnected from negative (-) battery terminal | 200 Ω or higher | DCM (telematics transceiver)*1 |
| G98-19 (CANL) - G57-4 (CG) | |||
| G98-9 (CANH) - G57-4 (CG) | Cable disconnected from negative (-) battery terminal | 200 Ω or higher | Central gateway ECU (network gateway ECU) |
| G98-20 (CANL) - G57-4 (CG) | |||
| G98-10 (CANH) - G57-4 (CG) | Cable disconnected from negative (-) battery terminal | 200 Ω or higher | Option connector (bus buffer ECU)*2 |
| G98-21 (CANL) - G57-4 (CG) | |||
| G98-11 (CANH) - G57-4 (CG) | Cable disconnected from negative (-) battery terminal | 200 Ω or higher | Central gateway ECU (network gateway ECU) |
| G98-22 (CANL) - G57-4 (CG) |
- *1: w/ Telematics Transceiver
- *2: w/ CAN Compatible Optional Devices
HINT:
If there is a short to ground in a CAN bus line without any CAN compatible optional devices connected to the option connector, repair or replace the CAN bus branch line or the option connector.
| Result | Proceed to |
|---|---|
| OK | A |
| NG (Line to central gateway ECU (network gateway ECU)) | B |
| NG (Line to ECU or sensor) | C |
| B | .gif) | GO TO STEP 3 |
| C | | GO TO STEP 4 |
|
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| 2. | CHECK FOR SHORT TO GND IN CAN BUS LINE (NO. 4 CAN JUNCTION CONNECTOR) |
(a) Disconnect the G99 No. 4 CAN junction connector.
(b) Measure the resistance according to the value(s) in the table below.
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| *1 | DLC3 | - | - |
| *a | Front view of wire harness connector (to No. 4 CAN Junction Connector) | *b | to Radio Receiver Assembly |
| *c | to Stereo Component Equalizer Assembly (w/ Active Noise Control System) | - | - |
Standard Resistance:
| Tester Connection | Condition | Specified Condition | Connected to |
|---|---|---|---|
| G99-1 (CANH) - G57-4 (CG) | Cable disconnected from negative (-) battery terminal | 200 Ω or higher | Radio receiver assembly |
| G99-12 (CANL) - G57-4 (CG) | |||
| G99-2 (CANH) - G57-4 (CG) | Cable disconnected from negative (-) battery terminal | 200 Ω or higher | Stereo component equalizer assembly* |
| G99-13 (CANL) - G57-4 (CG) |
- *: w/ Active Noise Control System
| OK | | REPLACE NO. 4 CAN JUNCTION CONNECTOR |
| NG | | GO TO STEP 4 |
| 3. | CHECK FOR SHORT TO GND IN CAN BUS LINE (NO. 4 CAN JUNCTION CONNECTOR - CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU)) |
(a) Disconnect the G66 central gateway ECU (network gateway ECU) connector.
(b) Measure the resistance according to the value(s) in the table below.
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| *1 | DLC3 | - | - |
| *a | Front view of wire harness connector (to No. 4 CAN Junction Connector) | *b | to Central Gateway ECU (Network Gateway ECU) |
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| G98-9 (CANH) - G57-4 (CG) | Cable disconnected from negative (-) battery terminal | 200 Ω or higher |
| G98-20 (CANL) - G57-4 (CG) | ||
| G98-11 (CANH) - G57-4 (CG) | Cable disconnected from negative (-) battery terminal | 200 Ω or higher |
| G98-22 (CANL) - G57-4 (CG) |
| OK | | REPLACE CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU) |
| NG | | REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (NO. 4 CAN JUNCTION CONNECTOR - CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU)) |
| 4. | CHECK FOR SHORT TO GND IN CAN BUS LINE (ECU OR SENSOR) |
(a) Reconnect all wire harness connectors.
(b) Disconnect the connector that includes terminals CANH and CANL from the ECU or sensor to which the bus line shorted to GND is connected.
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(c) Measure the resistance according to the value(s) in the table below.
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| *1 | DLC3 | - | - |
| *a | Component with harness connected (Central Gateway ECU (Network Gateway ECU)) | - | - |
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| G66-6 (CA3H) - G57-4 (CG) | Cable disconnected from negative (-) battery terminal | 200 Ω or higher |
| G66-21 (CA3L) - G57-4 (CG) |
HINT:
- If the resistance changes to 200 Ω or higher when the connector is disconnected from the ECU or sensor, there may be a short in the ECU or sensor.
- If the resistance does not become normal when the connector is disconnected from the ECU or sensor, check for a short to ground in the wire harness and repair or replace the wire harness or connector if necessary.
| OK | | REPLACE ECU OR SENSOR |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR |
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