ABS Faults - Task No 5 - Monday 16th March 2015

Plan:

Retrieve vehicle information and record on Job Card.  Gather equipment and tools required.  Undertake vehicle checks and conduct a start to ensure correct prior operation.  Apply VPE.


Task Requirements:

• Check condition of Front Pads & Discs and Report.
• Check ABS Sensors and their operation and Report.
• Use Diagnostic Equipment.
• Complete Knowledge Questions (within Portfolio).
• Complete Blog.
• Report to Assessor with analysis and diagnosis.
• Account for all tools and equipment and tidy work area.

Analysis Front Brake Pads and Disc (NSF)

Manufacturer's Data

Manufacturer's Data states the following:

Minimum Disc Thickness (Ventilated) - 21.5 mm

Maximum Disc Runout - 0.04 mm

Minimum Pad Thickness - 2 mm

Diagnosis

Measuring Pads

Measuring Disc
Thickness

Pads were removed and measured using a steel rule.  Pads measured 10 mm and are serviceable.  Brake Disc was removed and thickness measured using a Micrometer.  Disc thickness was ascertained to be 23.65 mm.  The disc was reattached to the hub in order to measure Runout using a DTI Gauge.  A reading of 0.19 mm was recorded and exceeds Manufacturer's recommendations.  Accordingly 2 new front Brake Discs are required.

Measuring Disc
Runout

Analysis ABS Sensors

Manufacturer's Data specifies an expected output voltage of 1.3 Volts, and a resistance of between 1280 and 1920 Ohms.

Diagnosis

Suspect broken/missing tooth on Reluctor Ring OSF

I disconnected the NSF ABS Sensor and probed the connector with a Multimeter set to K/Ohms, in order to test resistance.  The reading returned was 1.643 K/Ohms (1643 Ohms) NSF, and 1.639 K/Ohms (1639 Ohms) OSF which are within manufacturer's specifications.  I then connected a Picoscope and 

Damaged Reluctor Ring Tooth OSF

commenced a programme to establish sensor output voltage. Sensor output was established at 2.235 Volts.  Although this reading is higher than the researched Manufacturer's specification, there may be a variance between sensor types used.  The pattern returned indicated that the sensor was operating satisfactorily, and also indicated an issue with the

NSF Sensor Pattern

OSF reluctor ring, probably a broken or missing tooth.  This was confirmed after a visual inspection of the rear of the steering knuckle.  The reluctor ring is a component that is fitted to the end of the CV Boot at the end of the Drive Shaft and requires replacement accordingly.  NSF operation was within Manufacturer's specifications and operating correctly within expected parameters.

Analysis Fault Codes:

Customer stated that ABS warning light had illuminated.

Diagnosis:

I connected the Autel Diagnostics scanner via the vehicle DLC and began a search for DTCs accordingly.  The initial listing of returned DTCs was subsequently erased and a new search begun.  This search returned "No Codes Found".  Recommend customer continues to drive the vehicle in order to see if any further MIL illuminate, and return for further analysis should they do so.

Initial DTCs returned and cleared