22 · Diagnostics

Abs working irregularly

Make: Fiat
Model: 500 Factory Service Manual
Year: 2007–2024
Section: Brakes › Abs working irregularly

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Fault diagnosisAbs working irregularly

ABS WORKING IRREGULARLY

1.2 8v, 1.3 Multijet, 1.4 16v

When the brakes are operated briskly and suddenly (emergency braking) the ABS does not work properly and, as a result, one or more of the wheels is partly locked

0	PRELIMINARY CHECKS	All OK	Problems encountered	Operation
		Test results
	Turn the ignition ON and check that the "ABS failure" warning light comes on for around 4 seconds and then goes out	Move on to Step 1	The "ABS failure" warning light comes on and stays on.	Proceed as instructed in the See table K060 ABS FAILURE WARNING LIGHT ON
1	CHECK USING DIAGNOSTIC EQUIPMENT	All OK	Problems encountered	Operation
	Connect the Examiner diagnostic equipment to the diagnostic socket and check: that there are no faults in the ABS control unit; the plausibility of all the parameters.	Move on to Step 2	1. Error detected in the control unit. 2. No communication with the control unit 3. Fault detected in one of the front sensors. 4. Fault detected in one of the rear sensors. 5. Fault detected in one of the front wheel hubs. 6. Fault detected in one of the rear wheel hubs.	1. Continue following the instructions on the diagnostic equipment 2. Restore connection between the ABS control unit and the diagnostic connector See E7020 ABS 3. Replace the sensor Op. 3340A30 RPM SENSOR (ONE) FOR ONE FRONT WHEEL, LEFT OR RIGHT - R.R. 4. Replace the sensor Op. 3340A34 LEFT OR RIGHT REAR WHEEL RPM SENSOR (ONE) - R.R. 5. Replace the wheel hub Op. 4450C10 FRONT STEERING KNUCKLE (ONE), L/H OR R/H COMPLETE WITH WHEEL HUB - R+R WITH WHEEL REMOVED - CHECK WHEEL GEOMETRY SEPARATELY 6. Replace the wheel hub Op. 4450D10 HUB FOR ONE REAR WHEEL, L/H OR R/H - R+R WITH WHEEL REMOVED - CHECK WHEEL GEOMETRY SEPARATELY
2	ACTIVE DIAGNOSIS WITH DIAGNOSTIC EQUIPMENT	All OK	Problems encountered	Operation
	Keeping the diagnostic equipment connected carry out the active diagnosis of: pump motor; solenoid valves.	Move on to Step 3	Fault detected in one of the solenoid valves.	Replace the electrohydraulic unit - ABS electronic control unit Op. 3340A12 ABS HYDRAULIC AND ELECTRONIC CONTROL UNIT - R.R.
3	BRAKE CALIPER CHECK	All OK	Problems encountered	Operation
	Check the sliding of the brake caliper control pistons.	Move on to Step 4 for the 1.2 8v and 1.3 Mjet 16v versions Move on to Step 5 for all versions	1. Front caliper pistons seized. 2. Rear caliper pistons seized.	1. Replace the front brake calipers Op. 3310A30 FRONT BRAKE CALIPER (ONE) - R.R 2. Replace the rear brake calipers Op. 3310B36
4	CHECK ON FRONT BRAKE CALIPER AND SHOE CONTROL CYLINDER	All OK	Problems encountered	Operation
	Check that the shoe control cylinders are working properly.	Move on to Step 5	1.Front caliper pistons seized. 2.Shoe control cylinder not working properly.	1. Replace the front brake calipers Op. 3310A30 FRONT BRAKE CALIPER (ONE) - R.R 2.Replace the shoe control cylinder Op. 3320B20 REAR BRAKE SHOE CYLINDER (ONE) LEFT OR RIGHT - REPLACE.
5	CHECK ON PIPES / HOSES AND BLEED BRAKES	All OK	Problems encountered	Operation
	Visually inspect that there are no bends or constrictions in the brake pipes, bleed the system and check that the fluid comes out evenly from the bleed screws.	End of diagnosis.	Bends or constrictions present, the fluid does not come out evenly.	Replace the section of pipe affected by the problem.

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Parts & tools for this job For 2007 Fiat 500

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