- Short to GND in CAN main bus wire
- Short to GND in CAN branch wire
- Central gateway ECU (network gateway ECU)
- ECM
- Combination meter assembly
- Air conditioning amplifier assembly
- Power steering ECU assembly
- Certification ECU (smart key ECU assembly)
- Airbag ECU assembly
- Main body ECU (multiplex network body ECU)
- Brake actuator assembly (skid control ECU)
- Steering sensor
- Parking brake ECU assembly
- Meter mirror sub-assembly*1
- Stereo component equalizer assembly*2
- Headlight ECU sub-assembly LH*3
- Hybrid vehicle control ECU
- No. 2 CAN junction connector
- No. 3 CAN junction connector
Lexus NX: Check Bus 2 Line for Short to GND
Lexus NX Service Manual / Power Source & Network / Networking / Can Communication System / Check Bus 2 Line for Short to GND
DESCRIPTION
There may be a short circuit between one of the CAN bus wire and GND when there is no resistance between terminal 18 (CA4H) of the central gateway ECU (network gateway ECU) and terminal 4 (CG) of the DLC3, or terminal 17 (CA4L) of the central gateway ECU (network gateway ECU) and terminal 4 (CG) of the DLC3.
| Symptom | Trouble Area |
|---|---|
|
*1: w/ Headup Display
*2: w/ ASC System *3: for Triple Beam Headlight | |
| There is no resistance between terminal 18 (CA4H) of the central gateway ECU (network gateway ECU) and terminal 4 (CG) of the DLC3, or terminal 17 (CA4L) of the central gateway ECU (network gateway ECU) and terminal 4 (CG) of the DLC3. | |
WIRING DIAGRAM
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CAUTION / NOTICE / HINT
CAUTION:
When performing the confirmation driving pattern, obey all speed limits and traffic laws.
NOTICE:
- Inspect the fuses for circuits related to this system before performing the following procedure.
- Before measuring the resistance of the CAN bus, turn the power 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 (-) auxiliary battery terminal and leave the vehicle for 1 minute or more before measuring the resistance.
-
After turning the power switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal.
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When disconnecting and reconnecting the auxiliary battery.
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HINT:
When disconnecting and reconnecting the auxiliary battery, there is an automatic learning function that completes learning when the respective system is used.
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Some parts must be initialized and set when replacing or removing and installing parts.
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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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After performing repairs, perform the DTC check procedure and confirm that the DTCs are not output again.
DTC check procedure: Turn the power 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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- When replacing the combination meter assembly, always replace it with a new one. If a combination meter assembly which was installed to another vehicle is used, the information stored in it will not match the information from the vehicle and a DTC may be stored
HINT:
- Operating the power switch, any switches or any doors triggers related ECU and sensor communication with the CAN, which causes resistance variation.
- Even after DTCs are cleared, if a DTC is stored again after driving the vehicle for a while, the malfunction may be occurring due to vibration of the vehicle. In such a case, wiggling the ECUs or wire harness while performing the inspection below may help determine the cause of the malfunction.
PROCEDURE
| 1. | CHECK FOR SHORT TO GND IN CAN BUS WIRE (NO. 2 CAN JUNCTION CONNECTOR) |
(a) Disconnect the cable from the negative (-) auxiliary battery terminal.
(b) Disconnect the No. 2 CAN junction connector.
| *a | Front view of wire harness connector (to No. 2 CAN Junction Connector) | *b | to Hybrid Vehicle Control ECU |
| *c | to Stereo Component Equalizer Assembly (w/ ASC System) | *d | to Central Gateway ECU (Network Gateway ECU) |
| *e | to No. 3 CAN Junction Connector | *f | to Certification ECU (Smart Key ECU Assembly) |
| *g | to Combination Meter Assembly | *h | to Meter Mirror Sub-assembly (w/ Headup Display) |
| *i | to Airbag ECU Assembly | *j | Front view of DLC3 |
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition | Connected to |
|---|---|---|---|
|
*1: w/ ASC System
*2: w/ Headup Display | |||
| I93-1 (CANH) - I182-4 (CG) | Cable disconnected from negative (-) auxiliary battery terminal | 200 Ω or higher | Hybrid vehicle control ECU |
| I93-11 (CANL) - I182-4 (CG) | |||
| I93-2 (CANH) - I182-4 (CG) | Cable disconnected from negative (-) auxiliary battery terminal | 200 Ω or higher | Stereo component equalizer assembly*1 |
| I93-12 (CANL) - I182-4 (CG) | |||
| I93-4 (CANH) - I182-4 (CG) | Cable disconnected from negative (-) auxiliary battery terminal | 200 Ω or higher | Central gateway ECU (network gateway ECU) |
| I93-14 (CANL) - I182-4 (CG) | |||
| I93-5 (CANH) - I182-4 (CG) | Cable disconnected from negative (-) auxiliary battery terminal | 200 Ω or higher | No. 3 CAN junction connector |
| I93-15 (CANL) - I182-4 (CG) | |||
| I93-6 (CANH) - I182-4 (CG) | Cable disconnected from negative (-) auxiliary battery terminal | 200 Ω or higher | Certification ECU (smart key ECU assembly) |
| I93-16 (CANL) - I182-4 (CG) | |||
| I93-7 (CANH) - I182-4 (CG) | Cable disconnected from negative (-) auxiliary battery terminal | 200 Ω or higher | Combination meter assembly |
| I93-17 (CANL) - I182-4 (CG) | |||
| I93-9 (CANH) - I182-4 (CG) | Cable disconnected from negative (-) auxiliary battery terminal | 200 Ω or higher | Meter mirror sub-assembly*2 |
| I93-19 (CANL) - I182-4 (CG) | |||
| I93-10 (CANH) - I182-4 (CG) | Cable disconnected from negative (-) auxiliary battery terminal | 200 Ω or higher | Airbag ECU assembly |
| I93-20 (CANL) - I182-4 (CG) | |||
| Result | Proceed to |
|---|---|
| OK | A |
| NG (Central gateway ECU [network gateway ECU] branch wire) | B |
| NG (No. 3 CAN junction connector CAN main wire) | C |
| NG (Wire to ECU or sensor) | D |
| A | .gif) | REPLACE NO. 2 CAN JUNCTION CONNECTOR |
| C | | GO TO STEP 4 |
| D | | GO TO STEP 6 |
|
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| 2. | CONNECT CONNECTOR |
(a) Reconnect the I93 No. 2 CAN junction connector.
|
| 3. | CHECK FOR SHORT TO GND IN CAN BUS WIRE (CENTRAL GATEWAY ECU [NETWORK GATEWAY ECU] - NO. 2 CAN JUNCTION CONNECTOR) |
(a) Disconnect the central gateway ECU (network gateway ECU) connector.
| *a | Front view of wire harness connector (to Central Gateway ECU [Network Gateway ECU]) | *b | Front view of DLC3 |
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| I160-18 (CA4H) - I182-4 (CG) | Cable disconnected from negative (-) auxiliary battery terminal | 200 kΩ or higher |
| I160-17 (CA4L) - I182-4 (CG) |
| OK | | REPLACE CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU) |
| NG | | REPAIR OR REPLACE CAN BRANCH WIRE OR CONNECTOR (CENTRAL GATEWAY ECU [NETWORK GATEWAY ECU] - NO. 2 CAN JUNCTION CONNECTOR) |
| 4. | CONNECT CONNECTOR |
(a) Reconnect the I93 No. 2 CAN junction connector.
|
| 5. | CHECK FOR SHORT TO GND IN CAN BUS WIRE (NO. 3 CAN JUNCTION CONNECTOR) |
(a) Disconnect the No. 3 CAN junction connector.
| *a | Front view of wire harness connector (to No. 3 CAN Junction Connector) | *b | to Air Conditioning Amplifier Assembly |
| *c | to Power Steering ECU Assembly | *d | to Headlight ECU Sub-assembly LH (for Triple Beam Headlight) |
| *e | to Main Body ECU (Multiplex Network Gateway ECU) | *f | to No. 2 CAN Junction Connector |
| *g | to ECM | *h | to Brake Booster with Master Cylinder Assembly (Skid Control ECU) |
| *i | to Steering Sensor | *j | to Parking Brake ECU Assembly |
| *k | Front view of DLC3 | - | - |
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition | Connected to |
|---|---|---|---|
| *: for Triple Beam Headlight | |||
| I94-1 (CANH) - I182-4 (CG) | Cable disconnected from negative (-) auxiliary battery terminal | 200 Ω or higher | Air conditioning amplifier assembly |
| I94-11 (CANL) - I182-4 (CG) | |||
| I94-2 (CANH) - I182-4 (CG) | Cable disconnected from negative (-) auxiliary battery terminal | 200 Ω or higher | Power steering ECU assembly |
| I94-12 (CANL) - I182-4 (CG) | |||
| I94-3 (CANH) - I182-4 (CG) | Cable disconnected from negative (-) auxiliary battery terminal | 200 Ω or higher | Headlight ECU sub-assembly LH* |
| I94-13 (CANL) - I182-4 (CG) | |||
| I94-4 (CANH) - I182-4 (CG) | Cable disconnected from negative (-) auxiliary battery terminal | 200 Ω or higher | Main body ECU (multiplex network gateway ECU) |
| I94-14 (CANL) - I182-4 (CG) | |||
| I94-6 (CANH) - I182-4 (CG) | Cable disconnected from negative (-) auxiliary battery terminal | 200 Ω or higher | No. 2 CAN junction connector |
| I94-16 (CANL) - I182-4 (CG) | |||
| I94-7 (CANH) - I182-4 (CG) | Cable disconnected from negative (-) auxiliary battery terminal | 200 Ω or higher | ECM |
| I94-17 (CANL) - I182-4 (CG) | |||
| I94-8 (CANH) - I182-4 (CG) | Cable disconnected from negative (-) auxiliary battery terminal | 200 Ω or higher | Brake booster with master cylinder assembly (skid control ECU) |
| I94-18 (CANL) - I182-4 (CG) | |||
| I94-9 (CANH) - I182-4 (CG) | Cable disconnected from negative (-) auxiliary battery terminal | 200 Ω or higher | Steering sensor |
| I94-19 (CANL) - I182-4 (CG) | |||
| I94-10 (CANH) - I182-4 (CG) | Cable disconnected from negative (-) auxiliary battery terminal | 200 Ω or higher | Parking brake ECU assembly |
| I94-20 (CANL) - I182-4 (CG) | |||
| Result | Proceed to |
|---|---|
| OK | A |
| NG (No. 2 CAN junction connector CAN main wire) | B |
| NG (Wire to ECU or sensor) | C |
| A | | REPLACE NO. 3 CAN JUNCTION CONNECTOR |
| B | | REPAIR OR REPLACE CAN MAIN WIRE OR CONNECTOR (NO. 3 CAN JUNCTION CONNECTOR - NO. 2 CAN JUNCTION CONNECTOR) |
|
| 6. | CHECK FOR SHORT TO GND IN CAN BUS WIRE (ECU, 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.
| *a | Component with harness connected (Central Gateway ECU [Network Gateway ECU]) | *b | Front view of DLC3 |
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| I160-18 (CA4H) - I182-4 (CG) | Cable disconnected from negative (-) auxiliary battery terminal | 200 Ω or higher |
| I160-17 (CA4L) - I182-4 (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.
| OK | | REPLACE ECU OR SENSOR |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR |
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