traction control FIAT PUNTO 1994 176 / 1.G Workshop Manual

9*2 Braking system
2.3a Release tho locking clip ...
1 General information
The braking system is of the vacuum servo-assisted. dual-circuit hydraulic type. The arrangement of Ihe hydraulic system is such that each circuit operates one front ond ono rear brake from a tandem master cylinder. Under normal circumstances, both circuits operate In unison However, in the event of hydraulic failure in one circuit, lull braking force will still be available at two diagonally-opposite wheels. All models covered in this manual are fitted with front disc brakes and rear drum brakes. The front disc brakes are aotuated by single-piston sliding lype calipers, which ensure lhat equal pressure is applied to each brake pad. The rear drum brakes incorporate leading and trailing shoes, which are actuated by twin-piston wheel cylinders. A self-adjust mechanism is incorporated, to automatically compensate for brako shoe wear. As the brake shoe linings wear, the footbrnke operation automatically operates the adjuster mechanism, which effectively lengthens the shoe strut and repositions the brake shoes, to remove the llning-to-drum clearance. The mechanical handbrake linkage operates the brake shoos via a lever attached to the trailing brake shoe.
2.3b ... and remove the pad wear indicator wiring and brake fluid line from the suspension strut Load sensitive proportioning valves operate on the rear brake hydraulic circuits, to prevent the possibility of the rear wheels locking before the front wheels under heavy braking. Note: When servicing any part of the system, work carefully and methodically; also observe scmpulous cleanliness when overhauling any part of the hydraulic sysiem. Always renew components (in axle sets, where applicable) if In doubt about their condition, and use only genuine Fiat replacement parts, or at least those of known good quality. Note the warnings given in Safety first and at relevant points in this Chapter concerning fhe dangers of asoestos dust and hydraulic fluid.
Models with anti-lock braking system (ABS) Available as an option on certain models, the anti-lock braking system prevents skidding which not only optimises stopping distances but allows full steering control to be maintained under maximum braking. By electronically monitoring the speed of each roadwheel in relation to the other wneete, Ihe system can detect when a wheel is about to lock-up, before control is actually lost. The brake fluid pressure applied to that wheel's brake caliper is then decreased and restored (or modulated) several times a second until control
£s
regained. The system components comprise an Electronic Control Unit (ECU), four wheel speed sensors, a hydraulic unit, brake lines and dashboard mounted warning lamps.
The hydraulic unit incorporates a tandem master cylinder, a valve block which modulates the pressure in the brake hydrauli: circuits during ABS operation, an accumulator which provides a supply of highly pressursed brake fluid, a hydraulic pump to charge Ihe accumulator and an integral electronic control unit (ECU). The four wheel sensors are mounted on the wheel hubs. The ECU uses the signals produced by the sensors to calculate Ihe rotational speed of each wheel, The ECU has a self-diagnostic capability and will inhibit the operation of the ABS il a fault is detected, lighting the dashboard mounted warning lamp. The braking system will then revert lo conventional. non-ABS operation. II the nature of the laull ie not immediately obvious upon inspection, the vehicle must be taken to a Fiat dealer, who will have the diagnostic equipment
required
lo interrogate the ABS ECU electronically and pin-point the problem
2 Front brake pads - & renewal S

A


Warning: Renew BOTH sets ol front brake pads at the same
time
- NEVER renew the pads on
only
one wheel, as uneven braking may result

A


Warning: Note that the dust created by wear of the pads
may
contain asbestos, which is a health hazard. Never blow It out with compressed air, and don't inhale any of
it.
An approved filtering mask should be worn when working on the brakes. DO NOT use petrol or petroleum-based solvents to clean brake parts; use proprietary braks cleaner or methylated spirit only. 1 Firmly apply the handbrake, then jack up the front of the car and support it securely
on
axle stands (see Jacking and vehicle supporti. Remove the front roadwheeis. 2 Wording on one side of the vehicle, puth the caliper piston into its bore by pulling the caliper outwards. If necessary, press the piston back into its bore using a large G-clamp or a piston retraction tool. Keep a careful eye on the level of brake llufd in Ihe I reservoir as you do this - ensure that the
level
I does not rise above the MAX marking. 3 Whore applicable, release the locking dp and remove the pad wear indicator
wiring end
brake fluid line from the bracket at Ihe
base of
the suspension strut (see illustrations).
Petrol models without ABS 4 Remove the locking clip and exlracl the lower guide pin from the caliper (see illustrations) 5 Pivot the caliper body upwards and support In position with a length of wire or a cabie-fc. Avoid straining the hydraulic hose.
2,4a Remove the locking clip ... 2.4b ... and extract the lower guide pin from the caliper (petrol models without ABS)

Body electrical systems 12*9
3 Undo the mounting screws and lift out the speaker (see Illustration). Unplug the wiring at the connector. 4 Refitting is a reversal of removal,
Rear parcel shelf speakers 5 Working underneath the relevant parcel shetf support bracket, remove the securing screws and lower the loudspeaker from the support bracket. Unplug the wiring at the connector (see illustration). 6 Refitting is a reversal of removal.
11 Radio aerial - J^s removal and refitting ^
Removal 1 Carefully prise off the plastic cap. then remove the securing screws and withdraw the aerial from the roof. 2 Oraw the aerial co-axial cable through the roof aperture and disconnect it. If there is insufficient slack In the aerial cable, remove the courtesy light unit/overhead panel from the inside of the vehicle (as described earlier in this Chapter) to gain access to the cable connector,
Refitting 3 Refitting Is a reversal of removal, but ensure that seal between the aerial housing and the roof panel is in good condition.
12.2 Removing the radio/cassette unit using the special extraction tools
12.3 Disoonnect the wiring plugs from the rear of the unit. Note the bayonet fuse (arrowed) which is a push fit In the rear of the unit
10.3 Lift out the speaker and unplug the wiring at the connector
12 Radio/cassette player -removal and refitting ^
Removal Note: Once the battery has been disconnected, the radio/cassette unit cannot be re-activated until the appropriate security code has been entered. Do not remove the unit unless the appropriate code Is known. 1 Disconnect the battery negative terminal (refer to Disconnecting the battery in the Reference Section of this manual). 2 Insert the special extraction tools supplied with the vehicle into the holes on either side of the radio/cassette unit. Press them home until the Internal clips can be felt to release (see illustration). 3 Pull the unit forwards from the facia, then disconnect the wiring plugs and the aerial lead from the rear of the unit. Note the bayonet fuse, which is a push fit in the rear of the unit, (see illustration).
Refitting A Refitting is a reversal of removal, ensuring that the wiring Is routed freely behind the unit.
13 Speedometer drive cable - % removal and refitting Ss ^
Note: Later vehicles are fitted with an electronic transducer in place of the mechanical speedometer drive. This is mounted on the fransm/ss/on casing; refer to Chapter 7A, Section 3, for details.
Removal 1 Remove the instrument panel as described in Section 7. 2 Working in the engine compartment, unscrew the sleeve securing the cable end to gearbox, then pull the cable from gearbox. 3 Where applicable, release the cable from the brackets in the engine compartment bulkhead, then pull the cable through into the engine compartment. If necessary, pull the cable grommet from the bulkhead.
10.S Lower the loudspeaker from the support brackot and unplug tho wiring at the connector
Refitting 4 Refitting is a reversal of removal, bearing in mind the following points: a} Ensure that the bulkhead grommet is securely seated. b) Refit the instrument panel with reference to Section 7. c) Note that certain models have alignment marks on the cable outer for use when refitting. The marks should be aligned with the bulkhead bracket when the cable is correctly refitted and routed.
14 Switches -removal and refitting ^
Steering column stalk switches Note: On vehicles equipped with sfeezing wheel-mounted radio controls, the column stalk switch unit also incorporates the rotary contacts for the steering wheel switches. Removal 1 Disconnect the battery negative cable and position it away from the terminal. Turn the steering wheel so that the roadwheeis are pointing in the straight-ahead position. 2 Refer to Chapter 10 and remove the steering wheel from the column. 3 Remove the screws and lift off the upper and lower steering column shrouds. 4 Using an Allen key. slacken Ihe clamp ring at the rear of the switch unit (see illustration),
14.4 Using an Allen key, slacken the clamp ring at the rear of the switch unit