Fault-Tracing Information
Fault-tracing
Checking video signal
Troubleshoot
1. Search for cause of fault in Trailer module (TRM).
2. If no defects are found in Trailer module (TRM) the problem is likely with the CAN-communication.
Was a fault detected?
Yes - Verification
No - Troubleshooting CAN-net
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Verification
Verification
Access to the vehicle is necessary for the following checks.
- Activate parking camera in the menu.
- Activate distance information in the menu.
- Ignition position II or engine running.
- Engage reverse gear.
Check that:
- An image of what is behind the vehicle is shown on the front display screen.
- Help lines change when the steering wheel is turned.
- Help lines are shown for the vehicle's lateral position as well as bars for any objects behind the vehicle.
Is the function OK?
Yes - VERIFIED
No - VERIFICATION FAILED
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VERIFICATION FAILED - Information
VERIFIED - FAULT FOUND
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Information
Attempt New Test - Checking video signal
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Replacing the control module
If no defects were found on CAN-cables, change Parking Assistance Camera (PAC).
Other information
- Parking Aid Camera Module Parking Aid Camera Module
Continue - Verification
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Troubleshooting CAN-net
Fault-tracing
General information
Note! During this fault-tracing use the wiring diagram to assist when taking readings.
The diagnostic trouble code (DTC) is stored in the event of communication faults on the low speed side of the control area network (CAN). There can be a number of causes for faults in the communication:
- Intermittent open-circuits in one or both CAN cables in part of the network
- Intermittent short-circuits between the CAN cables
- Intermittent short-circuits between one of the CAN cables and ground or supply voltage
- Fault in the communication circuit in one or more control modules
- Internal fault in a control module on the CAN network that results in the control module transmitting faulty messages on the CAN network.
Note! In the event of a diagnostic trouble code (DTC) for a communication fault in a control module, the central electronic module (CEM) must also be checked for diagnostic trouble codes (DTCs). The central electronic module (CEM) monitors the voltage level in the CAN cables. The central electronic module (CEM) is the only control module that can directly store a diagnostic trouble code (DTC) for a short-circuit in one of the cables for ground or supply voltage. Do not replace the central electronic module (CEM) in the event of a CAN fault unless fault-tracing has indicated that the central electronic module (CEM) has an internal fault.
In order to check the control area network (CAN) cables, the resistance in the network must be measured.
Other information
Continue -
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Taking reading on cables in the CAN network (LS-CAN)
- Ignition off
- Disconnect the battery negative lead.
- Remove the central electronic module (CEM)
- Connect the breakout box to the cable harness for the central electronic module (CEM). Do not connect the central electronic module (CEM).
Hint: Where a breakout box cannot be used, take readings from the rear of the affected connectors if possible. This prevents terminal pins and socket housings being damaged.
Disconnect the CAN network to make it easier to locate a fault. A suitable point to disconnect the network is at the central electronic module (CEM). Fault-tracing therefore starts from the central electronic module (CEM).
Take resistance readings across the following terminals. Various readings must be taken due to the structure of the network. Twist the cable harness and work the connectors during each measurement to identify any intermittent short-circuits.
Note! The following resistance readings only measure the main arteries in the low speed network, not the junctions that exist for some control modules. If an open-circuit is suspected in a cable, or a short-circuit is suspected in one of its junctions, the connector at the control module for this junction must be disconnected and the reading taken from there.
Take the following readings
- Resistance between C1:49and C1:50. Resistance should be 120 ohms.
Note! Measuring will only give value 120 ohms if the main circuit in the CAN-net is intact. If there is a short-circuit somewhere in the CAN-net (either main circuit or other branching) the resistance will be 0 ohms.
- The resistance between C1:49 and a connection to voltage as well as between C1:49 and a short-circuit to ground. The resistance must be infinite or very high (more than 1 Mohms).
- The resistance between C1:50 and a connection to voltage as well as between C1:50 and a short-circuit to ground. The resistance must be infinite or very high (more than 1 Mohms).
Turn the cable harness and wiggle the connectors along the cable harness to detect any intermittent open circuits or short-circuits on the CAN-leads.
Note! Any short-circuit detected on the CAN-net may be on the main circuit or on any branching running out to some control modules. However, it will not be possible to measure open circuit on any branching.
Hint: If a fault is found, try to disconnect the junction with the fault at a point further forward. Disconnect any connector/control module immediately before the measurement point and take the reading again. Try to locate the fault in this way.
Remedy as necessary.
Other information
- Battery, disconnecting Battery, Disconnecting
- Connecting the breakout box Connecting The Breakout Box. Central Electronic Module (CEM)
- Checking wiring and terminals Checking Wiring And Terminals
Was a fault detected?
Yes -
No -
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Checking the traffic load on the CAN cables
- Connect the central electronic module (CEM) to the breakout box
- Connect the battery.
- Ignition on.
Note! When the adapter cable harness and the central electronic module (CEM) have been connected, there is access to both sides of the CAN network (both LS-CAN and HS-CAN). There will also be traffic on both networks. Be careful to check the terminals between which the readings are to be taken so that the intended reading is not taken on the wrong network.
Faults in the CAN network may be due to a control module sending faulty messages that disrupt "normal" communication. When messages are sent incorrectly, this results in a considerable increase in the amount of traffic on the CAN network. Check the load by measuring the average voltage value on the CAN cables in relation to ground.
Check as follows:
- Measure the voltage between C1:49 and ground. The voltage shall be approx. 2.3 V.
- Measure the voltage between C1:50 and ground. The voltage shall be approx. 2.8 V.
Other information
- Battery, disconnecting Battery, Disconnecting
Is the value OK?
Yes -
No -
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Identifying a control module in the CAN network
If the load on the CAN network is too high, this may be due to a control module transmitting faulty messages on the CAN network. This is called a disruptive control module. The fault may also be due to an intermittent short-circuit to supply voltage or ground in one of the CAN cables. This results in the control modules on the CAN network starting to send faulty messages. An intermittent short-circuit may occur without a diagnostic trouble code (DTC) being stored by any of the control modules.
Note! It is not necessarily the control module(s) that stored the diagnostic trouble code (DTC) that is communicating faultily. Faulty messages can come from any control module in the same section of the CAN network. However, faulty communication in one network cannot affect the communication on the other network. In other words, faulty communication on LS-CAN cannot disrupt communication on HS-CAN and vice versa.
Check communication/load on CAN-net by measuring voltage between C1:49 and C1:50. The voltage's average value shall be approx. 0.5 V (permitted is 0.4 to 0.6 V). In case of communication error, the voltage is approx. 0.7 V and higher.
In order to identify which control module is communicating incorrectly, cut the power supply to one control module at a time. Check the voltage in the CAN cables again. The easiest way to cut the power supply is to remove the fuse(s) for the relevant control module. Continue until the voltage between the CAN cables drops to approximately 0.5 V.
Hint: When the suspected control module has been identified, connect and disconnect the supply voltage to the control module a number of times to verify that the fault appears and disappears. Switch off the ignition between each check.
Note! Do not cut the power to the central electronic module (CEM) unless it is the last control module left to check.
A control module that is communicating incorrectly must be replaced. Remedy as necessary.
Note! Following a fault involving control modules that disrupt communication, other control modules may operate in Limp-Home mode (i.e. they work but with limited functionality) even after switching the ignition off and on a number of times. To remedy this, disconnect and reconnect the battery negative terminal to restore the control modules to normal function.
Remedy as necessary.
Other information
Continue -
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Verification
Hint: Once a fault has been repaired, conduct a verification to check that the fault has been remedied.
- Reinstall the connectors, components etc.
- Ignition on
- Erase diagnostic trouble codes (DTCs) in all control modules.
- Start the car. Allow the car to run for 10 minutes.
Read out the diagnostic trouble codes in the vehicle.
Does the diagnostic trouble code (DTC) for faulty communication return?
Yes -
No - FAULT FOUND
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Fault-tracing information
Attempt New Test -
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Fault-tracing without result
Information
Fault-tracing information
Verification shows that the fault is no longer present. The diagnostic trouble code (DTC) was probably caused by an intermittent fault.
Fault-tracing for this diagnostic trouble code (DTC) is not followed by a verification.
You can view the information again or exit fault-tracing for this diagnostic trouble code (DTC).
Do you want to view information again?
Yes - Attempt New Test
No - No Fault Found
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Attempt New Test -
No Fault Found - DONE
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FAULT FOUND - Verification
DONE - Verification
FAULT-TRACING FAILED - Replacing the control module
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