Communication Problems With the Volvo Scan Tool
Fault-Tracing Information
NOTE: Before commencing fault tracing check that the correct memory cassette is being used.
Fault sources:
- 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 (engine not running); connect a battery charger or extra battery.
Checking The Power Supply
- Ignition off.
- Connect the Volvo Scan Tool (ST) to the 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) power 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 an voltmeter between data link connector (DLC) terminal 16 and ground.
The voltmeter should read battery voltage.
If the reading is OK:
- Continue with checking data link connector (DLC) power ground.
If the reading is abnormal:
- Continue with checking fuse 14.
Checking Fuse 14
- Check that fuse 14 is intact.
If the fuse is OK:
- Continue with checking voltage before fuse 14.
If the fuse is not OK:
^ Check the cable between data link connector (DLC) terminal 16 and fuse 14 for a short-circuit to ground. Checking Cabling and Connections
Checking Voltage Before Fuse 14
- Ignition off.
- Connect a voltmeter between ground and fuse holder battery side output for fuse 14.
The voltmeter should read battery voltage.
If the reading is OK:
^ Check the cable between fuse 14 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 14 and battery positive terminal for an open-circuit. 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 31/67 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
See Volvo Scan Tool (ST).
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 31/53 for an open-circuit. Checking Cabling and Connections
Checking Communication With Another On-board Diagnostic (OBD) System,
(The ABS System For Example)
- Ignition off.
- Connect the Volvo Scan Tool (ST) to the 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 before fuse 4.
If the reading is abnormal:
If the ohmmeter reads infinity there is an open-circuit in the cable.
^ Check the cable between the sensor module connector terminal 9 and junction point 34/18 for an open-circuiT. 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. 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 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 34/18 and between junction point 34/18 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.
See Volvo Scan Tool (ST).
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 34/18 and between junction point 34/18 and the control modules connected to that junction point for a short-circuit to supply voltage. Checking Cabling and Connections
Checking 30-supply Before Fuse 4
- Ignition off.
- Remove fuse 4.
- Check that fuse is OK.
- Connect a voltmeter between ground and fuse holder positive side for fuse 4.
The voltmeter should read battery voltage.
If the reading is OK:
- Continue with checking 30 supply to the SRS sensor module.
If the reading is abnormal:
^ Check the cable between fuse 4 and main fuse 11A:1 for an open-circuit. 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 when "checking the communication cable for open circuits to th SRS system".
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 SRS sensor module. SRS Sensor Module - Replacement
If the reading is abnormal:
If the voltmeter reads approx. 0 V there could be an open-circuit in the cable between the ignition switch and SRS sensor module connector terminal 5.
- Continue checking.
Checking The X Supply From The Ignition Switch
- Ignition off.
- Disconnect battery negative lead.
- Disconnect the connector from the ignition switch
- Switch ignition 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 the cable between ignition switch terminal X and SRS sensor module connector terminal 5 for an open-circuit. Checking Cabling and Connections
If the readings are abnormal:
^ Check the cable between battery positive terminal and ignition switch terminal 30 for an open-circui. Checking Cabling and Connections