Electrical Accessory Panel: Description and Operation

ABS wheel sensor wiring -Jan 1996 (natural gas powered engines)

Note: There are approximately 150 cars with factory-installed natural gas powered engines which have solenoid valves on the firewall. Solenoid valves can interfere with signals from the ABS sensors. Deal with these cars as follows.





Customers have complained that the brake pedals in model year 1996 cars pulse, and that there is some noise when braking at low speeds. However, no reduction in braking performance or other faults have been reported. If the above occurs, it is due to the ABS system carrying out a self-diagnosis at low speed, which can be a result of high resistance in one of 4 cable splices in the front wheel sensor cable harness. The cables have a thin plastic film on the inside of the insulation to make them more flexible, and there may be a residue of this plastic film in the cable splice crimp. The wiring has been remedied in production from February 1996. The correct material, and cars that have been remedied, are marked with a green dot (decal or paint) under the fusebox cover on the white edge of the integrated relay/fusebox. This Service Bulletin describes how to cut and re-splice suspect cable splices. After re-splicing the ABS system should be tested accordingly.

Preparations:
Disconnect battery negative lead. Remove wiper arms. Remove cover from windscreen wiper well.





Remove electrical distribution unit cover (4 torx)
Cut tape on cable duct (at A).
Remove clip holding cable on brake pipe.
Remove cable harness from clip on wiper bracket.
Remove screws holding central electrical unit.
Lift the central electrical unit from its box and place on the edge of the windscreen wiper well.





Remove all relays in terminals 201-215
Reinstall central electrical unit in its box.
Install one screw to temporarily hold the central electrical unit in place.





Remove cable harness covers





Remove fuse panel (3 screws)
Remove rubber grommets
Lift the fuse panel to access cables.





Identify two spliced cable pairs (4 cable slices) 2 brown and 2 black cables. These cables may be black-white and brown-white.
The cable colors can be as illustrated.
Expose cable splices by pulling them out





Cut one cable pair

Caution: Only cut one cable pair at a time so as to avoid confusion. Take great care not to damage other cables. Use good lighting when cutting cables!

One cable splice can be pulled forward relatively easily.
Try to pull the other cable splice to the same as the cable harness.
If this is not possible cut the cable pair as close to the cable splice as possible and pull out sideways. Locate and pull out the other end of the cut cable pair.

Joining:





^ Thread 2 heat-shrink tubes onto the new ABS sensor cables.





Cut cable splice on both cables
Strip insulation on the 4 cables 13 mm with pliers 951 2620.





There may be a thin plastic film residue on the white (tinned) conductor units.
Untwist the stripped cable ends a little and twist them together again. For safety reasons, do the same with all four stripped cable ends.





Note: The (brown/black) cable pair are twisted around each other. It is important that paired cables are paired in the same way as earlier, before they are re-spliced. They should be twisted approximately 3 turns per 100 mm.





Splice the same cable ends that were previously spliced.
Insert crimping sleeve 967777 into the crimping tool 951 2649, in crimping slot "A" (This is easier on a workbench).
Squeeze the crimping tool a little to secure the crimping sleeve in the tool.





Take the crimping tool with crimping sleeve to the car
Put both cable ends in the crimping sleeve in the tool.
Insert cables in crimping sleeve so that their insulation comes up to but not into the crimping sleeve. Both cables should be inserted from the same direction (parallel).

Note: Insert cables in the crimping tool on the side without text!

Press crimping sleeve tight.
Check by hand that crimping sleeve is secure.





When one cable pair has been spliced, cut and splice the remaining cable pair
When the cable ends are joined, solder the tops of the conductors outside the crimping sleeves. This work may only be carried out by a professional, accustomed to soldering electrical components.
Set up an extractor by the soldering site.
Take care of adjacent cables. If necessary set up a heat shield.
Heat the crimping sleeve/conducting unit ends with the soldering iron. Heat thoroughly. Apply solder so that some runs into the crimping sleeve covering the conducting units.





Installing heat-shrink tubing on cable splice
^ Fold both cable splices as illustrated (arrow).
^ Carefully pull the heat-shrink tubing over the soldered cable splices. (The cable ends should be inside the tubing).
^ Heat the heat-shrink tubing

Note: The heat-shrink tubing is intended to provide good electrical insulation. Only one cable should protrude from the ends of the heat- shrink tubing.





^ Hold a putty knife behind the heat-shrink tubing and heat at close range using a hot air gun. Heat heat-shrink tubing quickly to avoid overheating the cable insulation.

Caution: The heat-shrink tubing should be totally crimped around the crimping sleeve. The ends should be sealed.





^ If necessary set up a heat deflector.
^ Twist the cables as much as possible before reinstalling into cable duct.





Reinstall central electrical unit
Check that the black box for the central electrical unit is loosely secured with a screw. (This is to facilitate installing the central electrical unit.)
Lower the central electrical unit into the black box. This may be difficult.)
Screw central electrical unit into place with 3 screws.
Check that all fuses are in place.
Screw clamp into place over cable harness.





Remove screw and pull up black box
Place it on the edge of the windscreen wiper well.
Install and tighten the second clamp (by arrow) to the cable harness. (This is easier to do when the black box is lifted up.)





Install relays





Press the black box into place
It may help to hold the auxiliary cable duct clip (at A) out of the way with a putty knife.
Screw the 4 screws holding the black box to the bodywork into place.
Install and screw fusebox cover into place.
Install a tie strap on the auxiliary cable duct (at A, instead of the tape)
Secure cable harness to the brake pipe with the clip. Secure cable harness to wiper bracket with a clip as before.

Note: Lift fusebox cover. Paint a green spot on the white edge of the integrated relay/fusebox to show that the cable splices have been remedied.

Finishing
Install:
^ Cover on windscreen wiper well
^ Wiper arms
^ Battery negative terminal Enter radio code if anti-theft coded radio installed.

Checking ABS system after repair Method

Note: It is important that the following checks are made in the correct order.

^ Connect Volvo Scan Tool (ST). Select: MONITOR TEST/ENTER/SCROLLING LIST/ENTER/LIST 1/ENTER/
^ Rotate right front wheel.
^ Check signal from right front wheel.
^ Connect left wheel sensor. (Connect connector at left ABS sensor.)
^ Rotate left front wheel.
^ Check signal from left front wheel.
^ Test drive the car.
^ Carry out a brake test.
^ Use the Volvo Scan Tool (ST) to check that there are no diagnostic trouble codes (DTCs).