Headlight Control Module (Hcm) Diagnostic Trouble Codes: Overview Volvo XC70 II

GENERAL INFORMATION

Note. Figures shown are only examples.

For general information about CAN-troubleshooting, see

1. see «GENERAL INFORMATION ABOUT FAULT-TRACING IN THE CAN NETWORK»(ref-495323-S26252627522012082100000)

General about CAN-related diagnostic trouble codes.

CEM-U000100/CEM-U000111/CEM-U000112/CEM-U000188 (HS CAN) or CEM-U001000/CEM-U001011/CEM-U001012/CEM-U001088 (MS-CAN) is generated when an electrical fault is detected in the CAN cables. Start with these diagnostic trouble codes first.

CEM-U01XX00 - CEM-U02XX00 indicates that Central electronic module (CEM) does not get a reply from, or has lost communication with, some control module on the CAN-net.

XXX-U000100/XXX-U000188 (HS-CAN) or XXX-U001000/XXX-U001088 (MS-CAN) can be generated in all CAN-connected control modules. For emission-related faults, diagnostic trouble code XXX-U007300 may also be stored. These diagnostic trouble codes indicate that the control module has detected interference on the CAN-net or another communication fault.

XXX-U010000 - XXX-U029900 can be stored in all CAN-connected control modules. These diagnostic trouble codes indicate that the control module does not receive any reply from or has lost communication with any control module on the CAN-net.

XXX-U030000 can be stored in all CAN-connected control modules except in Central electronic module (CEM). The control modules on the CAN-net listen for a message (identity number) that is sent out at regular intervals from Central electronic module (CEM). This diagnostic trouble code indicates that the control module has not received any identity number, or that the expected number is not correct. Interference on the CAN-net can also store this diagnostic trouble code.

XXX-U04XXXX - XXX-U05XXXX can be stored in all CAN-connected control modules. These diagnostic trouble codes (deviations may occur) indicate that the control module has received invalid data from another control module on the CAN-net. It may also indicate that the control module has, due to signal from another control module, limited its own functionality.

Note. In case of CAN-related faults, it is likely that a combination of above diagnostic trouble codes occur.

Note. After fault with control modules that interfere with communication, other control modules may remain in Limp-Home (that is, they work with reduced functionality) even when the ignition has been turned off and on a few times. For certain faults in the CAN-net where control modules have stopped communicating, it may help to disconnect/reconnect the battery to "restart" the control module/CAN-net.

If a communication diagnostic trouble code can be read from the control module, the malfunction is probably intermittent. Intermittent fault in the voltage supply and ground to a control module on the CAN network results in the Central electronic module (CEM) storing a diagnostic trouble code (DTC) for an open-circuit in communication with the control module where the voltage supply does not work. There will probably not be a diagnostic trouble code (DTC) in the control module where the open-circuit in the voltage supply occurred as the control module cannot store a diagnostic trouble code (DTC) when it is not supplied with power.

Note. Central electronic module (CEM) should not be replaced in case of CAN-fault, unless troubleshooting reveals that Central electronic module (CEM) has an internal fault.

Scheme 4

1. Continue Refer to «CHECKING RESISTANCE IN CAN-NET»(ref-495399-S35772909742012082100000)

Scheme 5

Scheme 6

1. Ignition off.
2. Disconnect the battery negative lead.
3. Connect OBDII-Box (951 3015) to the diagnostics socket. HINT: Use the appropriate wiring diagram to provide support when taking readings. For general information about fault-tracing the control area network (CAN), see the linked document below. see «GENERAL INFORMATION ABOUT FAULT-TRACING IN THE CAN NETWORK»(ref-495323-S26252627522012082100000) Measure resistance between the following connections on the OBDII-box/diagnostics socket. #6 and #14. The resistance should be approx. 55 - 65 ohms. If resistance is approx. 120 ohms, this indicates open circuit in the circuit so that only one terminating resistor (120 ohms) has been measured. If resistance is above 1 kohms this indicates open circuit/high contact resistance somewhere in the circuit. If resistance is below 55 ohms this indicates short-circuiting/contact resistance between the CAN-lines somewhere in the circuit. HINT: For HS-CAN the terminating resistors are located in Central electronic module (CEM) and in Engine control module (ECM). Twist the cable harness and wiggle connectors where they can be accessed along the cable harness during every measurement, and note if the resistance changes to detect intermittent short-circuits or open circuit. NOTE: Resistance measurement measures only main lines in the CAN-net (in circuit where both terminating resistors are found), not branches to certain control modules. See appropriate wiring diagram for vehicle model in question. Open circuit on branching without a terminating resistor cannot be detected with this measurement. However, short-circuiting on a branch can be detected. To measure resistance in the CAN-net to control modules located in a branching of their own, the measurement shall be done against the CAN-net at that control module. The values shall be as above. NOTE: After fault with control modules that interfere with communication, other control modules may remain in Limp-Home (that is, they work with reduced functionality) even when the ignition has been turned off and on a few times. For certain faults in the CAN-net where control modules have stopped communicating, it may help to disconnect/reconnect the battery to "restart" the control module/CAN-net. Remedy wiring as necessary. Other information see «BATTERY DISCONNECTING AND CONNECTING»(ref-495407-S17646253862012082100000) see «CHECKING WIRING AND TERMINALS»(/volvo/xc70/ii-2007-2013/remont/body-electrical/#wiring-and-terminals-general-diagnostics-and-tests)

Was a fault detected?

1. YES Refer to «VERIFICATION»(ref-495399-S15183848072012082100000)
2. NO Refer to «CHECKING SHORT-CIRCUITING TO GROUND/VOLTAGE IN CAN-NET»(ref-495399-S23660487032012082100000)

Scheme 7

Scheme 8

1. Connect the battery.
2. Ignition on.
3. Connect OBDII-Box (951 3015) to the diagnostics socket. HINT: Use the appropriate wiring diagram to provide support when taking readings. For general information about fault-tracing the control area network (CAN), see the linked document below. see «GENERAL INFORMATION ABOUT FAULT-TRACING IN THE CAN NETWORK»(ref-495323-S26252627522012082100000) 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. The load can be checked by reading the average value of the voltage on the CAN cables in relation to ground. Measure voltage between the following connections on the OBDII-box/diagnostics socket. #6 and #4 (ground). The voltage should be approx: 2, 8 - 3, 2 V. #14 and #4 (ground). The voltage should be approx: 1, 8 - 2, 2 V. #6 and #14. The voltage shall be between approx. 0.55-1.4 V. The voltage shall normally be between 0.55 - 0.90 V. A higher voltage may indicate increased traffic on the CAN-net. In case of fault in communication/too high traffic on the CAN-net, the voltage is considerably higher than the above stated values. NOTE: After fault with control modules that interfere with communication, other control modules may remain in Limp-Home even when the ignition has been turned off and on a few times. For certain faults in the CAN-net where control modules have stopped communicating, it may help to disconnect/reconnect the battery to "restart" the control module/CAN-net. 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. HINT: DiCE can be used as fault detection tool if fault is suspected on the CAN-net that cannot be detected with normal troubleshooting. Interference, intermittent faults, faulty messages on the CAN-net (chattering control modules) etc., are examples of such faults. The tool registers fault messages used on the CAN-net. Fault messages may be caused by short intermittent malfunctions on the CAN-net or by a control module sending fault messages. See tools: 951 3010 as well as associated TJ 20402. Ignition on. Connect DiCE to the diagnostics socket. Note the blue LED-indicator. The indicator flashes to show detection of fault messages. NOTE: Certain interference may occur without any real fault Cable fault Shake the cables lightly and pull lightly on the connections during the check to locate any fault. Note the blue LED-indicator. "Chatting" control modules "Chatting" control modules may be difficult to find and troubleshooting may take time. Let the vehicle stand with DiCE connected for an extended time period. Afterwards, activate functions to provoke a malfunction. It may take up to several hours before the fault messages are sent. When the indicator starts to flash, remove the fuse for one control module at a time until the indicator stops flashing. When the indicator stops flashing, restore the fuse for the relevant control module and check that the indicator starts to flash again. Then it is likely that the problem is identified. Other information see «BATTERY DISCONNECTING AND CONNECTING»(ref-495407-S17646253862012082100000) see «CHECKING WIRING AND TERMINALS»(/volvo/xc70/ii-2007-2013/remont/body-electrical/#wiring-and-terminals-general-diagnostics-and-tests)

Was a fault detected?

1. YES Refer to «IDENTIFYING A CONTROL MODULE IN THE CAN NETWORK»(ref-495399-S33959175702012082100000)
2. NO Refer to «CHECKING VOLTAGE-DROP IN CABLE FOR CAN-H AND CAN-L, RESPECTIVELY»(ref-495399-S04729191102012082100000)

The diagnostic trouble code is stored when communication between Central electronic module (CEM) and relevant control module has been interrupted. There can be a number of causes for interruptions in the communication

1. Central electronic module (CEM) has stopped sending the signal that receiving control module (the control module that generated this fault code) expects.
2. Intermittent open-circuit in one or both CAN cables in part of the network
3. Intermittent short-circuits between the CAN cables
4. Intermittent short-circuits between one of the CAN cables and ground or supply voltage
5. Incorrect signal configuration in control module that set diagnostic trouble code. The fault can be due to a customer or workshop replacing a control module without downloading new software for the replacement.

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). Central electronic module (CEM) monitors the voltage level on the CAN-lines, and is the only control module that directly can set a diagnostic trouble code for short-circuiting to ground or to voltage for any of the leads. Central electronic module (CEM) shall not be replaced in case of CAN-fault, unless troubleshooting reveals that the module has an internal fault.

Corrective actions

1. If there are diagnostic trouble codes stored in several control modules that indicate lost communication on the CAN-net, first try to troubleshoot diagnostic trouble codes in Central electronic module (CEM).
2. If the problem is intermittent, erase the diagnostic trouble code and check that it is not generated again.
3. If there are only diagnostic trouble codes that indicate lost communication on the CAN-net stored in the control module that generated this trouble code, try to solve the problem by downloading new software to the control unit.
4. Check the cables in the controller area network (CAN) according to the following fault-tracing.

Other information

1. see «GENERAL INFORMATION ABOUT FAULT-TRACING IN THE CAN NETWORK»(ref-495323-S26252627522012082100000)
2. Go to the tab software and program the control module with the latest software.

1. Continue Refer to «VERIFICATION»(ref-495399-S12097617082012082100000)

Scheme 9

1. Ignition on
2. 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 via the DIAGNOSTICS tab. Check that the diagnostic trouble code (DTC) for faulty communication is not stored again.

Has the fault been remedied?

1. YES OKAY: Troubleshooting has been completed.
2. NO Refer to «TAKING READING ON CABLE IN THE CAN NETWORK (HS-CAN)»(ref-495399-S17080119092012082100000)

Scheme 10

1. Ignition off
2. Disconnect the battery negative lead.
3. Remove the central electronic module (CEM)
4. 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. 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 see «BATTERY DISCONNECTING AND CONNECTING»(ref-495407-S17646253862012082100000) see «CONNECTING THE BREAKOUT BOX»(ref-495323-S29210678802012082100000) see «SIGNAL SPECIFICATION»(ref-495325-S00863282382012082100000) see «CHECKING WIRING AND TERMINALS»(/volvo/xc70/ii-2007-2013/remont/body-electrical/#wiring-and-terminals-general-diagnostics-and-tests)

Was a fault detected?

1. YES Refer to «VERIFICATION»(ref-495399-S15149508462012082100000)
2. NO Refer to «CHECKING THE TRAFFIC LOAD ON THE CAN CABLES»(ref-495399-S37181084502012082100000)

The diagnostic trouble code is stored when communication between Central electronic module (CEM) and relevant control module has been interrupted. There can be a number of causes for interruptions in the communication

1. Central electronic module (CEM) has stopped sending the signal that receiving control module (the control module that generated this fault code) expects.
2. Intermittent open-circuit in one or both CAN cables in part of the network
3. Intermittent short-circuits between the CAN cables
4. Intermittent short-circuits between one of the CAN cables and ground or supply voltage
5. Incorrect signal configuration in control module that set diagnostic trouble code. The fault can be due to a customer or workshop replacing a control module without downloading new software for the replacement.

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). Central electronic module (CEM) monitors the voltage level on the CAN-lines, and is the only control module that directly can set a diagnostic trouble code for short-circuiting to ground or to voltage for any of the leads. Central electronic module (CEM) shall not be replaced in case of CAN-fault, unless troubleshooting reveals that the module has an internal fault.

Corrective actions

1. If there are diagnostic trouble codes stored in several control modules that indicate lost communication on the CAN-net, first try to troubleshoot diagnostic trouble codes in Central electronic module (CEM).
2. If the problem is intermittent, erase the diagnostic trouble code and check that it is not generated again.
3. If there are only diagnostic trouble codes that indicate lost communication on the CAN-net stored in the control module that generated this trouble code, try to solve the problem by downloading new software to the control unit.
4. Check the cables in the controller area network (CAN) according to the following fault-tracing.

Other information

1. see «GENERAL INFORMATION ABOUT FAULT-TRACING IN THE CAN NETWORK»(ref-495323-S26252627522012082100000)
2. Go to the tab software and program the control module with the latest software.

1. Continue Refer to «VERIFICATION»(ref-495399-S07173070852012082100000)

See also:
• DESCRIPTION OF FROZEN VALUES
• DESCRIPTION OF STATUS IDENTIFIER
• DESCRIPTION OF COUNTER
• LOCATION OF COMPONENTS
• CHECKING THE POWER SUPPLY AND GROUND TERMINAL
• CHECKING WIRING AND TERMINALS