Communication Problems With the Volvo Scan Tool
Fault Tracing Information
NOTE: Before commencing fault tracing check that the correct memory cassette is being used.
Cause of faults:
- Open-circuit, short-circuit to ground or short-circuit to supply voltage in the cable to the data link connector (DLC).
- Open-circuit in data link connector (DLC) power supply, power ground or signal ground.
- Open-circuit in SRS sensor module power supply.
- Defective Volvo Scan Tool (ST), Volvo Scan Tool (ST) cabling or adapter.
NOTE: If the communications problem only occurs in a stationary car with the ignition switched to position II or when starting the engine (not when the engine is running); connect a battery charger or extra battery.
^ Start fault tracing at checking the power supply.
Checking The Power Supply
- Ignition off.
- Connect Volvo Scan Tool (ST) to data link connector (DLC).
- Ignition on.
- Power up the Volvo Scan Tool (ST) with the switch on the adapter box. The adapter box, which is part of the Volvo Scan Tool (ST) kit, may sometimes be called the switch or just the adapter.
- Check that the display lights up.
The Volvo Scan Tool (ST) display should light up.
If the display lights up:
Check communication with another on-board diagnostic (OBD) system, the ABS system for example.
- Continue with checking communication with another on-board diagnostic (OBD) system, the ABS system for example.
If the display does not light up:
Check data link connector (DLC) supply.
- Continue with checking data link connector (DLC) power supply.
Checking Data Link Connector (DLC) Power Supply
- Ignition off.
- Disconnect Volvo Scan Tool (ST) from data link connector (DLC).
- Connect a voltmeter between data link connector (DLC) terminal 16 and ground.
The voltmeter should read supply voltage.
If the reading is OK:
- Continue with checking data link connector (DLC) power ground.
If the reading is abnormal:
- Continue checking.
Checking Fuse 15
- Check fuse 15.
If the fuse is OK:
- Continue with hecking voltage before fuse 15.
If the fuse is not OK:
^ Check the cable between data link connector (DLC) terminal 16 and fuse 15 for a short-circuit to ground. Checking Cabling and Connections
Checking Voltage Before Fuse 15
- Ignition off.
- Connect a voltmeter between ground and rear fuse holder battery side output for fuse 15.
The voltmeter should read supply voltage.
If the reading is OK:
^ Check the cable between fuse 15 and data link connector (DLC) terminal 16 for an open-circuit. Checking Cabling and Connections
If the reading is abnormal:
^ Check the cable between fuse 15 and battery positive terminal for an open-circuit in accordance with: Checking Cabling and Connections
Checking Data Link Connector (DLC) Power Ground
- Ignition off.
- Connect an ohmmeter between data link connector (DLC) terminal 4 and ground.
The ohmmeter should read approx. 0 Ohms.
If the reading is OK:
- Continue with checking data link connector (DLC) signal ground.
If the reading is abnormal:
If the ohmmeter reads infinity there is an open-circuit in the cable.
^ Check the cable between data link connector (DLC) terminal 4 and ground terminal 31/15 for an open circuit. Checking Cabling and Connections
Checking Data Link Connector (DLC) Signal Ground
- Ignition off.
- Connect an ohmmeter between data link connector (DLC) terminal 5 and ground.
The ohmmeter should read approx. 0 Ohms.
If the reading is OK:
^ Check adapter box supply.
If the reading is abnormal:
If the ohmmeter reads infinity there is an open-circuit in the cable.
^ Check the cable between data link connector (DLC) terminal 5 and ground terminal 31/15 for an open circuit in accordance with: Checking Cabling and Connections
Checking Communication With Another On-board Diagnostic (OBD) System, The ABS System For Example
- Ignition off.
- Connect Volvo Scan Tool (ST) to data link connector (DLC).
- Ignition on.
- Try to establish contact with another on-board diagnostic (OBD) system, the ABS system for example.
Communication with another on-board diagnostic (OBD) system established:
- Continue with checking the communication cable for open-circuits to the SRS system.
Communication with another on-board diagnostic (OBD) system not established:
- Continue with checking to see if the communications cable is short-circuited to ground.
Checking the communication cable for open circuits to the SRS system
- Ignition off.
- Disconnect battery negative lead.
- Disconnect Volvo Scan Tool (ST) from data link connector (DLC).
- Expose and remove SRS sensor module connector. SRS Sensor Module - Replacement
CAUTION: Never touch the sensor module pins. There is a risk of static discharge which could damage the sensor module.
- Connect an ohmmeter between data link connector (DLC) terminal 7 and sensor module connector terminal 9.
The ohmmeter should read approx. 0 Ohms.
If the reading is OK:
There is no open-circuit in the cable between data link connector (DLC) terminal 7 and SRS sensor module connector terminal 9.
- Continue with checking 30 supply to the SRS sensor module.
If the reading is abnormal:
If the ohmmeter reads infinity there is an open-circuit in the cable.
^ Check the cable between junction point 23/421 sensor module connector terminal 9 for an open-circuit in accordance with: Checking Cabling and Connections
Checking To See If The Communications Cable Is Short-circuited To Ground
- Ignition off.
- Make a note of radio code if anti-theft coded radio installed.
- Disconnect battery negative lead.
- Disconnect Volvo Scan Tool (ST) from data link connector (DLC).
- Expose and remove SRS sensor module connector.
CAUTION: Never touch the sensor module pins. There is a risk of static discharge which could damage the sensor module.
- Connect an ohmmeter between data link connector (DLC) terminal 7 and ground.
The ohmmeter should read approx. 20 Kohms (or a similarly high resistance). This reading depends on the number of on-board diagnostic (OBD) systems connected to the data link connector (DLC).
If the reading is OK:
The cable is not short-circuited to ground.
- Continue with Checking to see if the communications cable is short-circuited to supply voltage.
If the reading is abnormal:
If the ohmmeter reads approx. 0 Ohms there is a short-circuit to ground in the cable.
^ Check cable between data link connector (DLC) terminal 7 and junction point 23/421 and between junction point 23/421 and the control modules connected to that junction point for short-circuit to ground. Checking Cabling and Connections
Checking To See If The Communications Cable Is Short-circuited To Supply Voltage
- Ignition off.
- Disconnect battery positive lead.
- Connect an ohmmeter between data link connector (DLC) terminal 7 and battery positive lead.
The ohmmeter should read approx. 20 Kohms (or a similarly high resistance). This reading depends on the number of on-board diagnostic (OBD) systems connected to the data link connector (DLC).
If the reading is OK:
The cable is not short-circuited to supply voltage.
^ Check Volvo Scan Tool (ST), Volvo Scan Tool (ST) cabling and adapter box.
If the reading is abnormal:
If the ohmmeter reads approx. 0 Ohms there is a short-circuit to supply voltage in the cable.
^ Check cable between data link connector (DLC) terminal 7 and junction point 23/421 and between junction point 23/421 and the control modules connected to that junction point for a short-circuit to supply voltage in accordance with: Checking Cabling and Connections
Checking 30 Supply To The SRS Sensor Module
- Ignition off.
- The connector should have been disconnected from the SRS sensor module previously.
CAUTION: Never touch the sensor module pins. There is a risk of static discharge which could damage the sensor module.
- Switch ignition to position II.
- Connect a voltmeter between ground and SRS sensor module connector terminal 5.
The voltmeter should read battery voltage.
If the reading is OK:
There is no open-circuit in the cabling.
^ Replace sensor module.
If the reading is abnormal:
If the voltmeter reads approx. 0 V there is an open-circuit in the cable between overload relay 105 (2/30) and SRS sensor module connector terminal 5.
- Continue with checking 30-supply before fuse 32.
Checking 30-supply Before Fuse 32
- Remove fuse 32.
- Switch ignition to position II.
- Connect a voltmeter between ground and fuse holder positive side for fuse 32.
The voltmeter should read battery voltage.
If the reading is OK:
^ Check the cable between fuse 32 and SRS sensor module connector terminal 5 for an open-circuit in accordance with: Checking Cabling and Connections
If the reading is abnormal:
- Continue with checking overload relay signal ground.
Checking Overload Relay Signal Ground
- Ignition off.
- Screw off central electrical unit cover in engine compartment.
- Remove relay 105 from base.
- Ignition off.
- Connect an ohmmeter between terminal 4 on relay base 105 (2130) and ground.
The ohmmeter should read approx. 0 Ohms.
If the reading is OK:
- Continue with checking 30 supply to the overload relay.
If the reading is abnormal:
If the ohmmeter reads infinity there is an open-circuit in the cable.
^ Check the ground lead between relay base 105 (2130) terminal 4 and ground for an open-circuit. Checking Cabling and Connections
Checking 30 Supply To The Overload Relay
- Ignition off.
- Connect a voltmeter between terminal 1 on relay base 105 (2/30) and ground.
The voltmeter should read battery voltage.
If the reading is OK:
- Continue with checking the X supply to the overload relay.
If the reading is abnormal:
^ Check the cable between relay base 105 (2/30) terminal 1 and battery positive terminal for an open-circuit. Checking Cabling and Connections
Checking The X Supply To The Overload Relay
- Ignition on.
- Connect a voltmeter between terminal 2 on relay base 105 (2/30) and ground.
The voltmeter should read battery voltage.
If the reading is OK:
- Continue with checking 30 supply after overload relay.
If the reading is abnormal:
- Continue with checking the X supply from the ignition switch.
Checking 30 Supply After Overload Relay
- Ignition off.
- Connect an ohmmeter between relay base 105 (2130) terminal 3 and fuse holder positive side for fuse 32.
The ohmmeter should read approx. 0 Ohms.
If the reading is OK:
^ Try using a new relay.
If the reading is abnormal:
^ Check cable between relay base 105 (2/30) terminal 3 and fuse 32 for an open-circuit in accordance with: Checking Cabling and Connections
Checking The X Supply From The Ignition Switch
- Ignition off.
- Disconnect battery negative lead.
- Disconnect the connector from the ignition switch
- Turn ignition key to position II.
- First connect an ohmmeter between terminal X and terminal 30 on the ignition switch and then between terminal X and the other terminal 30 on the ignition switch.
In both cases the ohmmeter should read approx. 0 Ohms.
If both readings are OK:
Check ignition switch supply.
- Continue with checking ignition switch supply.
If any reading is abnormal:
^ Replace ignition switch.
Checking Ignition Switch Supply
- Ignition off.
- Connect battery negative lead.
- Ignition switch connector should be disconnected.
- First connect an voltmeter between terminal 30 on the ignition switch connector and ground and then between the other terminal 30 on the ignition switch connector and ground.
In both cases the voltmeter should read battery voltage.
If readings are OK:
^ Check cable between ignition switch terminal X and relay base 105 (2/30) terminal 2 for an open-circuit in accordance with: Checking Cabling and Connections
If the readings are abnormal:
^ Check the cable between battery positive terminal and ignition switch terminal 30 for an open-circuit in accordance with: Checking Cabling and Connections