Exhaust Emissions & Control (SI) - Task No 3 - Tuesday 21st April 2015

Plan

Gather all tools and equipment required and retrieve vehicle information for entry onto Job Card.

Task Requirements

• Establish Lambda Operating Voltages
• Establish correct functioning of Sensor
• Record Fault Codes
• Provide Graphs/Drawings of Performance Patterns
• Record Emissions at Tail Pipe
• Establish Fuel Injector Duration at Idle
• Complete Knowledge Questions
• Complete Blog
• Account for all Tools and Equipment and tidy work area
• Report to Assessor with Analysis and Diagnosis

Preliminary Vehicle Checks

Healthy Battery

Battery voltage was checked using a Voltmeter and returned a healthy reading of 12.82 Volts.  All other engine bay fluid levels were also checked and ascertained to be maintained at a satisfactory level for operation.

Analysis Fault Codes

Initial Search Results

Autel Diagnostics scanner was connected to vehicle ECU via the DLC and interrogated for DTCs accordingly.  Initial search was cleared and then a fresh search undertaken, which returned ""No DTCs Found".

System Pass

Sensor Location

4 Wire Zirconia Sensor Connector

Analysis Lambda Sensor Voltages

Manufacturer's Data suggests that expected operating voltages to be within the range of 0.2 Volts - 0.8 Volts (Lean to Rich).  The Sensor under examination is a 4 Wire Zirconia Pre-Cat O2 Sensor.  There are 2 White wires which are for the Heater Element, a Black wire for the Signal and a Grey wire for the Signal Earth Return.  All wiring and connections appeared to be integrally sound.  A Picoscope was then connected as per the on-board package instructions and then the engine started and allowed to reach operating temperature at idle RPM.

Diagnosis

Expected Pattern of correct Sensor operation

Pattern Retrieved (at Idle RPM)

Sensor Switching

The image returned was not as expected and initially suggested a faulty sensor.  However upon applying the throttle, the pattern performed correctly, moving between rich and lean accordingly.  








In order to test the heating element, the engine was turned off and the sensor disconnected. An Ohmeter was then used to probe the 2 white wires (Heater Element), which returned a reading of Infinity and confirmed a faulty sensor. Recommend R&R new Sensor and then confirm procedure with an emissions test accordingly.

Monday 27th April 2015

Analysis Injector Duration

A Picoscope was connected as per the on board package instructions and a test conducted to ascertain injector duration performance under a variety of throttle operating conditions.  Manufacturer's data suggests a pattern be retrieved within the parameters as displayed below:

Expected Pattern at Idle

Diagnosis Injector Duration

Images were captured at start up, throttling and idle, all of which met the expected parameters:

Start Up

Throttling

At Idle RPM (Measured)

Voltage peaked at 54.33 Volts (between 50-60 Volts recommended) and had a duration of 3.168 ms, indicating satisfactory performance.

Analysis Emissions Test

Manufacturer's Emissions Data

Manufacturer's Data was retrieved regarding permissible emissions and were listed as follows:

Oil Temp: 80 Degrees C
CO (idle): 0.5% Max
HC (idle): 100ppm
CO2 (idle): 14.5 - 16%
O2 (idle): 0.1 - 0.5 %

Emissions Results

Diagnosis Emissions Test

The vehicle failed to meet the minimum standards with an excessively high CO & HC content recorded.  Idle RPM appears higher than it should be, and it is recommended that the Throttle Potentiometer be checked, and the test re-initiated accordingly.