In this scan tool work sheet I worked on a Nissan Aviner.
The first task in this worksheet was to read the current data from the scan tool, these are the readings I got,
Engine load = off
Engine RPM (cmps) 1000 RPM
Throttle Angle (tps) 0.50v
Engine Coolant = 57 C
Fuel injection opening pulse = 3.2ms
Vehicle speed = 0 Km/h
Power steering condition = off
Air conditioning condition = off
MAF = 0.80v
After these reading where taken we needed to check the vehicle for fault codes, there where no fault codes present in the vehicles computer. After the initial scan we got the lecturer to put a fault under the hood without us knowing what it was, after this was done we re scanned the car and found a fault code,
Code number = 12 Mass Airflow sensor
After discovering that there was a fault in the MAF circuit we checked the current data again to see what changes had happened after the fault was introduced, this is the data we found different,
MAF = 0.30v instead of 0.80v
Throttle Angle = 5.1v instead of 0.50v
this told us straight away that it was just not the MAF circuit that had been affected so we came to the conclusion that 2 circuits had been afftected.
Visual Inspection
After looking under the hood we found the MAF sensor unplugged and the throttle position sensor unplugged, we plugged these back in to repair the fault.
We re checked the current data and found that the two circuits that had been affected had returned to normal operating conditions.
We rechecked the system for for codes, erased the old code and found the fault did not reappear.
After this I found the importance of live data when fault finding to be very helpful, as no code came up for the throttle position sensor I would have not realized that something was wrong with this circuit, the only was i saw this was with the difference in the live data readings.
Parameters are very important when fault finding, if you find a sensor working outside of its set parameters you can be sure something is wrong with that component.
Scan tools are only a aid when fault finding as they do not tell you what is wrong with the car, they just help you by identifying the circuit, but a fault code might not appear unless certain conditions are met.
