Fault-Tracing Information
Fault-tracing
General information
The diagnostic trouble code (DTC) is stored when the communication between the central electronic module (CEM) and the relevant control module has been interrupted. There can be a number of causes for interruptions in the communication:
- Faulty signal configuration in the control module that stored the diagnostic trouble code (DTC). The fault can be due to a customer or workshop replacing a control module without downloading new software for the replacement
- Intermittent open-circuit 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
The problem may also be due to defective software in a control module or hardware problem in the CAN-net (defective leads).
Note! If there is a diagnostic trouble code (DTC) for a communication fault in a control module, check whether diagnostic trouble codes (DTCs) have been stored in the central electronic module (CEM). The central electronic module (CEM) monitors the voltage level in the CAN cables and 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.
Corrective actions
1. If this diagnostic trouble code (DTC) is the only communication diagnostic trouble code (DTC) stored in one of the control modules in the high speed network, try to remedy the fault by downloading new software for the control module that stored the diagnostic trouble code (DTC)
2. Check the cables in the CAN network according to the following fault-tracing
Other information
- General information about fault-tracing in the CAN network Initial Inspection and Diagnostic Overview
- Go to the tab software and program the control module with the latest software.
Hint: If both PBM-U030000 and PBM-U014000 are stored, the likely problem cause is communication error with Central electronic module (CEM). Park Brake Module (PBM) shall not be replaced.
Continue - Verification
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Verification
- Ignition on
- Wait for 20 seconds.
Note! This first verification assumes that download of new software was required in the control module that generated the diagnostic trouble code. If download of new software was not required: read out diagnostic trouble codes and check if the code status is permanent or intermittent to learn how difficult it will be to find the fault.
Read out the diagnostic trouble codes in the vehicle.
Check that the diagnostic trouble code (DTC) for faulty communication is not stored again.
Has the fault been remedied?
Yes - FAULT FOUND
No - Taking reading on cable in the CAN network (HS-CAN)
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Taking reading on cable in the CAN network (HS-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 will be obtained due to the structure of the network. Twist the cable harness and work the connectors at accessible points along the cable harness in order to check whether the resistance changes during each measurement. This method can be used to detect intermittent short-circuits or open-circuits.
Note! The following resistance readings only measure the main arteries in the high speed network, not the junctions that exist for some control modules. See the Wiring diagram for the relevant car model. 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 C3:47 and C3:48. 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 C3:48 and a connection to voltage as well as between C3:48 and a short-circuit to ground. The resistance shall be very high (more than 1 Mohms).
- The resistance between C3:47 and a connection to voltage as well as between C3:47 and a short-circuit to ground. The resistance shall be very high (more than 1 Mohms).
Hint: Any short-circuit detected on the CAN-net may be on the main circuit or on any branching running out to some control modules. If a fault is found, try to disconnect the junction with the fault at a point further forward. Try to locate the fault in this way.
Remedy as necessary.
Other information
- Battery, disconnecting Battery Disconnecting
- Connecting the breakout box Connecting Breakout Box, Central Electronic Module (CEM)
- Checking wiring and terminals Checking Wiring and Terminals
Was a fault detected?
Yes - Verification
No - Checking the traffic load on the CAN cables
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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 C3:48 and ground. The voltage shall be approx. 2.3 V.
- Measure the voltage between C3:47 and ground. The voltage shall be approx. 2.8 V.
Other information
- Connecting the breakout box Connecting Breakout Box, Central Electronic Module (CEM)
- Battery, disconnecting Battery Disconnecting
Is the value OK?
Yes - Fault-tracing without result
No - Identifying a control module in the CAN network
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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 sending faulty messages on the CAN network (known as 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. The faults can occur without a diagnostic trouble code (DTC) being stored by the control modules. The voltage can be measured between the CAN cables in order to check the load on the CAN network.
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 of the CAN network. However, faulty communication in one network cannot affect the communication on the other network. In other words, faulty communication on the LS-CAN cannot disrupt communication on the HS-CAN and vice versa.
- Check communication/load on HS-CAN by measuring voltage between C3:48 and C3:47. 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. Ignition off 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.
The control module that is communicating incorrectly must be replaced.
Note! A faulty control module that disrupts communication can place other control modules 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.
Continue - Verification
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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 vehicle. Allow the vehicle to run for 10 minutes.
Read out the diagnostic trouble codes in the vehicle.
Is the diagnostic trouble code for configuration fault regenerated?
Yes - Fault-tracing information
No - FAULT FOUND
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Fault-tracing information
Attempt New Test - General information
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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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No Fault Found - DONE
Attempt New Test - General information
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