Troubleshooting
Troubleshooting
General information
Hint: For general information about troubleshooting in the Control Area Network (CAN), see the linked document below.
Note! When selecting the vehicle profile, the correct vehicle must be identified. Use the "Retrieve VIN" button. Troubleshooting may fail if this is not done.
In order to check the CAN cables, the resistance of the network must be measured. The resistance between the two high-speed CAN cables, with the network connected, must be 60 ohms. The acceptable range of this reading is approx. 55-65 ohms.
If the communication diagnostic trouble code can be read from the control module, the malfunction is probably intermittent.
An intermittent malfunction in the power supply to a control module is indicated by individual diagnostic trouble codes in the Central Electronic Module (CEM) (CEM-1A5X or CEM-1A6X, as appropriate). There is probably no diagnostic trouble code in the control module that the central electronic module (CEM) has generated, since the module cannot generate a diagnostic trouble code when it is not supplied with voltage.
Caution! During this troubleshooting use the wiring diagram as help when measuring.
Other information
Continue - Measuring cables in CAN-network (HS-CAN)
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Measuring cables in CAN-network (HS-CAN)
- Ignition off
- Disconnect the minus terminal on the battery.
- Connect a breakout box to the Engine Control Module (ECM).
Note! Also connect the engine control module (ECM) to the adapter cable harness, otherwise the measured values will be incorrect.
Hint: Use the applicable wiring diagrams as help when measuring.
Measure the resistance between the connections below. Due to the network design, different measurement values will be obtained. For each measurement, twist the cable harness and wiggle the connections, where accessible, to detect any intermittent short-circuits or open circuits.
Note! The following resistance measurements only measure the main paths in the high-speed network, not the junctions that exist for some control modules. See the applicable wiring diagram for the relevant car model. An open circuit in one path cannot be detected by this measurement. However, a short-circuit in a branch can be detected.
Measure the resistance between #B58 (#C58) and #B45 (#C45). The resistance shall be approx. 60 ohms. Permitted values approx. 55-65 ohms.
Also measure the resistance between each connection and the voltage as well as ground. The resistance must be infinite or very large (more than 1 Mohms).
Hint: If a malfunction is detected, then try to separate the junction with the measured malfunction at an appropriate point further along the cable. Unplug any connector/control module nearest to the previous measurement point and measure again. In this manner, try to find the malfunction.
Remedy the cables as necessary.
Other information
- Battery, disconnecting Battery Disconnecting
- Connecting the breakout box Connecting Breakout Box, Transmission Control Module (TCM)
- Signal description Signal Description. Transmission Control Module (TCM)
- Checking wiring and terminals Checking Wiring And Terminals
Was a malfunction 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 battery
- Ignition on
Malfunctions in the Control Area Network (CAN) may be due to a control module sending incorrect messages that disrupt normal communication. When messages are sent incorrectly, this results in a considerable increase in the amount of traffic on the Control Area Network (CAN). Check the load by measuring the average voltage value on the network cables in relation to ground.
Check in the following manner:
- Measure the voltage between #B45 (#C45) (HS-CAN-L) and ground. The voltage shall be approx. 2.3 V.
- Measure the voltage between #B58 (#C58) (HS-CAN-H) and ground. The voltage shall be approx. 2.8 V.
Other information
- Battery, disconnecting Battery Disconnecting
Is the value OK?
Yes - Troubleshooting 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 incorrect messages on the CAN network (known as a disruptive control module). The malfunction may also be due to an intermittent short-circuit to voltage or ground in one of the CAN-cables. This results in the control modules on the CAN-network starting to send incorrect messages. The malfunctions 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 incorrectly. Incorrect messages can come from any control module in the same section of the CAN-network. However, incorrect communication in one network cannot affect the communication on the other network. In other words, incorrect communication on the LS-CAN cannot disrupt communication on the HS-CAN, and vice versa.
Check the communication/load on the CAN-network by measuring the voltage between #B45 (#C45) and #B58 (#C58). The average value of the voltage shall be approx. 0.5 V (0.4-0.6 V). In case of malfunctioning communication, the voltage is at approx. 0.7 V and above.
To identify which control module is responsible for the incorrect communication, one can disconnect the voltage feed to each control module in turn and re-check the voltage on the CAN-cables. The voltage feed is most easily disconnected by removing the fuse/fuses for the particular control module. Continue until the voltage between the CAN-cables drops to about 0.5 V.
Note! When connecting and disconnecting individual control modules, other diagnostic trouble codes (DTCs) may be stored in certain control modules.
Hint: When a suspected control module is identified, connect and disconnect the voltage feed several times to verify that the malfunction appears and disappears. Turn off the ignition between each check.
Note! Do not cut the voltage to the central electronic module (CEM) unless it is the last control module left to check.
A control module which communicates incorrectly must be replaced. See Repair and installation/Removal, replacement and installation.
Note! Following a malfunction involving control modules that disrupt communication, other control modules may remain in Limp-Home mode (that is, they work but with limited functionality) even after the ignition has been turned off and on a number of times. To remedy this, disconnect and reconnect the battery's minus terminal to restore the control modules to normal function.
Continue - Verification
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Troubleshooting 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 - General information
No Fault Found - No Fault Found
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Verification
- Erase diagnostic trouble codes via Vehicle communication service.
- Start the engine and let it run for 10 minutes.
- Read out diagnostic trouble codes via Vehicle communication service.
Check to see if the communication diagnostic trouble code has been stored again.
Did the trouble code(s) return?
Yes - Troubleshooting information
No - Fault Found
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Troubleshooting information
Information
Fault-tracing information
The fault should have been detected and remedied. As this is not the case fault-tracing has failed.
Exit fault-tracing for this diagnostic trouble code (DTC) or make another attempt.
Do you want to exit fault-tracing?
Yes - FAULT-TRACING FAILED
No - Attempt New Test
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FAULT-TRACING FAILED - FAULT-TRACING FAILED
Attempt New Test - General information
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