22 · Diagnostics

Steering hard / (steering in both directions)

Make: Fiat
Model: Croma Factory Service Manual
Year: 2005–2010
Section: Steering – vehicle behaviour › Steering hard / (steering in both directions)

‹ Prev Excessive rolling/pitching - at rear Next › Steering hard / (in one direction only)

Fault diagnosisSteering hard / (steering in both directions)

STEERING HARD / (STEERING IN BOTH DIRECTIONS)

There is a noticeable hardening in the steering (in both directions) with no assistance.

The electric steering is known as MPU (motor pump unit) and is fitted directly on the steering box.

The failure warning light should go off with the engine running.

The MPU electric motor speed varies as the steering speed varies.

0	PRELIMINARY CHECKS	ALL OK	PROBLEMS ENCOUNTERED	ACTION
	Carry out a test steering fully in various conditions to check the actual onset of the hardening in both directions. Check: Presence of oil in the reservoir The oil level is between the minimum and the maximum The battery is run down (not below 10.5 Volt) The alternator is working properly Connectors correctly connected at the MPU See E7045 ELECTRIC STEERING	Move on to Step 1	1. No oil in the MPU reservoir	1.Add oil and bleed the system Op. 0010T75 HYDRAULIC POWER STEERING SYSTEM BLEED AIR
			2. Oil level not correct	2.Restore correct oil level
			3. Battery run down	3.Charge battery
			4. The alternator is not charging correctly	4.Check/Replace the alternator, if defective
			5. Connectors not correctly connected	5.Restore the correct connections
1	CHECK USING DIAGNOSTIC EQUIPMENT	ALL OK	PROBLEMS ENCOUNTERED	ACTION
	Connect the diagnostic equipment (Examiner or other instruments) to the electric steering node diagnostic socket and check: for the presence of any errors for the presence of any errors at the NBC for the presence of any errors at the NCM for the presence of any errors at the NAS correct impedance of the CAN presence of the SRS error at the system with ESP	Move on to Step 2	1. Errors present for the electric steering node	1. Continue as described by the diagnostic equipment
			2. CAN line from MPU to NBC faulty	2. Restore CAN line electrical connections from MPU to NBC
			3. CAN line from NCM to MPU faulty	3. Restore CAN line electrical connections from NCM to MPU
			4. CAN line from NGE to NAS	4. Restore the CAN line electrical connections from the NGE to the NAS
			5. Incorrect body proxy	5. Replace Body computer with correct proxy
2	STEERING ANGLE SIGNAL CHECK	ALL OK	PROBLEMS ENCOUNTERED	ACTION
	Connect the Examiner to the ABS control unit and, in the parmeters ambient, check the operation of the steering angle signal by turning the steering wheel clockwise (to the right) where the values should decrease and turning it anti-clockwise they should increase. The value should be zero with the wheels perfectly straight	Move on to Step 3	1. Value of parameter incorrect the vehicle has lost toe in	1.Zero the parameter by regulating the steering rods and checking that the control unit is working properly by turning the steering wheel to the end of travel position in both directions
			2. The steering wheel angle parameter value is always zero for the defective steering angle sensor	2.Replace the steering angle sensor, (on the pinion for systems with ABS or located on the steering wheel for systems with ESP)
				Cancel the errors, carry out a road test to ensure that the control unit checks whether the errors are still present,return to the workshop and check that the fault is no longer present using the diagnostic equipment.
3	STEERING ANGLE SENSOR SUPPLY CHECK	ALL OK	PROBLEMS ENCOUNTERED	ACTION
	Using the Examiner in the Voltmeter function, check that the supply for the steering angle sensor in the steering box is correct See Test 4110AB STEERING ANGLE SENSOR ON STEERING BOX CHECK	Move on to Step 4	2.Sensor supply not correct	1.Restore correct power supply.
		Move on to Step 4	2.Wiring between steering angle sensor and connector plate for the MPU broken/short circuited to earth	2.Renew the correct wiring
3	STEERING ANGLE SENSOR SUPPLY CHECK	ALL OK	PROBLEMS ENCOUNTERED	ACTION
	Using the Examiner in the Voltmeter function, check that the supply for the steering angle sensor on the steering wheel is correct See Test 3350EB STEERING ANGLE SENSOR OPERATION CHECK	Move on to Step 4	Sensor supply not correct	Restore correct power supply
4	SPEED SIGNAL CHECK	ALL OK	PROBLEMS ENCOUNTERED	ACTION
	Connect the EXaminer and check for the presence of the vehicle speed signal	Move on to Step 5	No speed signal	Restore the speed signal for the ABS node
5	CHECK USING DIAGNOSTIC EQUIPMENT	ALL OK	PROBLEMS ENCOUNTERED	ACTION
	Cancel the errors, disconnect the diagnostic station and place the key in the OFF position for about 10 secs. Start up the engine and turn the steering wheel to the end of travel position in both directions. Reconnect the Examiner diagnostic equipment and check that there are no errors at the electric steering control unit	End of diagnosis	The fault persists	Move on to Step 6
6	STEERING COLUMN CHECK	ALL OK	PROBLEMS ENCOUNTERED	ACTION
	Raise the vehicle at the front, check that the steering column rotates correctly by disconnecting it from the steering (take care not to rotate the steering column through more than 360° which could cause a loss of the reference position for the steering by the MPU	Move on to Step 7	Steering column hardness during rotation	Replace the MPU Op. 4130B25 POWER STEERING PUMP ASSEMBLY R R FOR VERSIONS WITH AIR CONDITIONER
7	RACK AND PINION CLEARANCE CHECK	ALL OK	PROBLEMS ENCOUNTERED	ACTION
	Check the pinion-rack clearance with the steering column detached and the wheels straight	Move on to Step 8	Pinion-rack clearance too large	Replace steering Op. 4130A15 POWER STEERING BOX R R WITH FRONT SUSPENSION FRAME REMOVED
8	BOOT CONDITION CHECK	ALL OK	PROBLEMS ENCOUNTERED	ACTION
	Remove the front wheels and the track rod ends from the hub. Check the condition of the boots.	Move on to Step 9	Boots broken	Lubricate the steering and replace the boots Op. 4120A30 LEFT OR RIGHT STEERING BOX BOOT (ONE) - REPLACE AT BENCH
9	CHECK ON SLIDING AND FASTENING OF RACK	ALL OK	PROBLEMS ENCOUNTERED	ACTION
	Check the sliding of the rack Check the bush-rack radial clearance Check the fastening of the steering box	Move on to Step 10	1.Steering hardness	1.Replace the steering Op. 4130A15 POWER STEERING BOX R R WITH FRONT SUSPENSION FRAME REMOVED
			2.Clearance too large	2.Replace the steering Op. 4130A15 POWER STEERING BOX R R WITH FRONT SUSPENSION FRAME REMOVED
			3. Fastening loose	3.Tighten the steering box fastening pins to torque.
10	STEERING ROD JOINTS CLEARANCE CHECK	ALL OK	PROBLEMS ENCOUNTERED	ACTION
	Check the clearance of the steering rod joints	Move on to Step 11	Joints seized or with clearance	Replace the rods Op. 4110B10 STEERING LINKS - R+R ON VEHICLE - CHECK TOE-IN/TOE-OUT SEPARATELY
11	HARDENING/STICKING CHECK	ALL OK	PROBLEMS ENCOUNTERED	ACTION
	Check that there is no hardening/sticking by rotating the hubs	Move on to Step 12	Clearance in the joint	Replace the joint Op. 4410B40 LOWER TRACK CONTROL ARM (WITH BALLJOINT) FOR LEFT OR RIGHT FRONT SUSPENSION (ONE) - R+R - CHECK WHEEL GEOMETRY SEPARATELY
12	STEERING WHEEL RETURN CHECK	ALL OK	PROBLEMS ENCOUNTERED	ACTION
	Refit all the components detached: Test the vehicle and check that the steering wheel returns correctly	Move on to Step 13	Steering wheel return poor	Restore front wheel geometry Op. 4450A10 FRONT WHEEL GEOMETRY - CHECK USING OPTICAL EQUIPMENT - INCLUDES ADJUSTMENT IF NECESSARY
13	CHECK ON CORRECT OPERATION	ALL OK	PROBLEMS ENCOUNTERED	ACTION
	Check that the fault is no longer present	End of diagnosis

‹ Prev Excessive rolling/pitching - at rear Next › Steering hard / (in one direction only)

Parts & tools for this job For 2005 Fiat Croma

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