ABS-143
D. ABS-143 Road speed signalDA. DTC information
Condition
The control module converts the signal from the front wheel sensors to a pulsed signal which is sent to the speedometer on the instrument panel (dashboard). The road speed signal is the average of the front wheel speeds. If the road speed of the slowest front wheel is over 40 km/h (24 mph) and the ABS control module registers that the pulse signals to the instrument panel cut out below 7ms, DTC ABS-143 will be posted.
Substitute value
None
Possible source
- Signal lead short circuiting to ground or current
- Break in signal cable
- Defective instrument panel (dashboard)
- Contact resistance in the connections
Note! A DTC may be posted for certain control modules if the ignition is switched on once the car's speed reaches approx. 6 km/h (4 mph) e.g. when being towed. These control modules can be identified by the identification code in the lower left corner of the control module product plate beginning with "M5..." for ABS control modules and with "P1..." for TRACS control modules. Faults caused in this way are not included in the fault-tracing.
Fault symptom(s)
No display of speed on the instrument panel. Other systems which use the road speed signal via the instrument panel can be affected.
Fault-tracing begins with DB. Other DTCs, status notifications and status checks.
DB. Other DTCs, status notifications and status checks
[DB1]
Other DTCs
Select one of the above alternatives to continue.
Alternative 1: DB2
Alternative 2: DB3
[DB2]
Status notification
Select one of the following alternatives to continue.
Alternative 1: Fault-trace as per DC.Circuit fault. Permanent fault.
Alternative 2: Fault-trace as per DD.Circuit fault. Intermittent fault.
[DB3]
Status check
- Test drive the vehicle.
- Disconnect the Volvo System Tester to abort the diagnosis.
Warning! The ABS and EBD systems are not available while Volvo Diagnosis is activated. Take great care when test driving as there is serious risk of the wheels locking when braking.
Check that the speedometer is working.
Does the speedometer work ?
Yes: Fault-trace as per DD. Circuit fault. Intermittent fault.
No: Fault-trace as per DC. Circuit fault. Permanent fault.
DC. Circuit fault. Permanent fault
[DC1]
Connect the test box and check the contact points
Connect test box as per JJJA. Connect the test box Connect the Test Box [JJJ]
Then proceed to: DC2
[DC2]
Check the signal cable resistance
- Ignition off.
- Control module disconnected.
- Uncover the instrument panel.
- Disconnect instrument panel contact A.
Connect an ohmmeter between #6 on the test box and combination instrument contact A connection 3.
The ohmmeter should indicate approx. 0 ohms.
If reading is OK: DC4
If reading is incorrect: DC3
[DC3]
Check for cable breaks
Check the cable between instrument panel contact A connection 3 and control module #6 for breaks as per [IIIB2]. Check Communication to Control Module [III]
Then continue with: DC13
[DC4]
Check the signal cable resistance to ground
- Ignition off.
- Instrument panel contact A disconnected.
- Control module disconnected.
Connect an ohmmeter between #6 and #8 on the test box.
The ohmmeter should indicate infinite resistance
If reading is OK: DC6
If reading is incorrect: DC5
[DC5]
Check for short circuiting
Check the cable between instrument panel contact A connection 3 and control module #6 for short circuiting to ground as per [IIIB3]. Check Communication to Control Module [III]
Then continue with: DC13
[DC6]
Check the signal cable short circuiting to power
- Ignition off.
- Instrument panel contact A disconnected.
- Control module disconnected
- Ignition on.
Connect a voltmeter between #6 and #8 on the test box.
The voltmeter should indicate approx. 0V.
If reading is OK: DC8
If reading is incorrect: DC7
[DC7]
Check for short circuiting
Check the cable between combination instrument contact A connection 3 and control module #6 for short circuiting to power as per [IIIB4]. Check Communication to Control Module [III]
Then continue with: DC11
[DC8]
Check the instrument panel
- Ignition off.
- Connect the control module.
- Connect the instrument panel.
- Raise the vehicle so that the back wheels are free.
- The engine ticking over.
- Engage gear so that the front wheels begin to rotate.
Note! DTCs may be registered when the rear wheels are still and the front wheels are rotating. Erase any DTC's in the ABS system after fault tracing.
Check that the speedometer is working
Note! Ensure that the front wheels are still when the gear selector/lever is moved.
Does the speedometer work ?
Yes: DC9
No: DC10
[DC9]
Fault causes and contact resistance and oxidation checks
The DTC has been caused by poor contact in the control module and instrument panel contacts. Check the contacts for contact resistance and oxidation and take appropriate action [IIIB5] Check Communication to Control Module [III]
Then continue with: Fault corrected
[DC10]
Replacing a component
Test with a new instrument panel.
Then continue with: DC13
[DC11]
Check the instrument panel
Hint: The instrument panel can be damaged as a consequence of a short circuit to power in the signal cable.
- Ignition off.
- Connect the control module.
- Connect the instrument panel.
- Raise the vehicle so that the front wheels are free.
- Engine ticking-over.
- Engage gear so that the front wheels begin to rotate.
Note! DTCs may be caused in the ABS system when the rear wheels are still and the front wheels are rotating. Erase any DTCs in the ABS system after fault-tracing.
Check that the speedometer is working.
Note! Ensure that the front wheels are still when the gear selector/lever is moved.
Does the speedometer work?
Yes: DC12
No: DC10
[DC12]
The speedometer works
The instrument panel is OK.
Then continue with: Fault corrected
[DC13]
Verification
Hint: After repair it is necessary to check that the fault has been rectified.
- Ignition off.
- Reconnect the contacts, components etc.
- Raise the vehicle so that the front wheels are free.
- Engine ticking-over.
- Engage gear so that the front wheels begin to rotate.
Note! DTCs may be registered in the ABS-system when the rear wheels are still and the front wheels are rotating. Erase any DTCs in the ABS system after fault-tracing.
Check that the speedometer is working.
Note! Ensure that the front wheels are still when the gear selector/lever is moved.
Does the speedometer work ?
Yes: Fault corrected
No: DC14
[DC14]
Fault-tracing information
The verification result shows that the fault persists.
Do you want to exit fault-tracing?
Yes: Fault not corrected
No: DC1
DD. Circuit fault. Intermittent fault
[DD1]
Check leads and connections
Check the instrument panel and control module contacts for contact resistance and oxidation as per [IIIB6]. Check Communication to Control Module [III]
Check the cable between the instrument panel contact A connection 3 and control module #6 for intermittent breaks as per [IIIB2], intermittent short circuiting to ground as per [IIIB3] and intermittent short circuiting to power as per [IIIB4]. Check Communication to Control Module [III]
Then continue with: DD2
[DD2]
Fault-tracing information
For intermittent faults fault-tracing is not followed by a verification because the fault is not present at this moment.
Do you want to repeat fault-tracing?
Yes: DD1
No: Operation done