Scan Tool Diagnostics

For this segment we used a Hanatec Scan Tool on a Toyota 1ZZ engine.

The table below is an example of live data from a scan tool.

A Scan Tool is a highly effective tool in diagnosing problems in a vehicle, as it narrows down problems for a faster diagnosis/repair. Live data is also really helpful as it shows what is happening, as it is happening.

Type of information(PID=Parameter Identification) Letters to describe it Value of data Units for data Engine Load(how much air comes in) AFM(MAF) 2.58 Gm/s Engine RPM Engine speed 700 RPM Throttle angle Throttle position 11 % Engine coolant temperature Coolant temperature 71 C Intake air temperature Intake air temperature 22 C Fuel Injection opening pulse Injector pulse width 2.7 ms Transmission select position shift 4 Vehicle speed 0 0 Km/h Oxygen sensor(s) O2 sensor B1 S1 0.890 V Fuel Trim Short fuel trim#1 -20.3 % Idle control IAC duty ratio 37.5 % Power steering condition PS off Air Conditioning condition A/C cut signal on Exhaust Gas Recirculation(EGR) - - - Fuel Evap or Purge condition EVAP VCV OFF - Malfunction Indicator Light Warning light/MIL on on

The diagnostic plug on this particular engine was located under the bench. If it was on a vehicle, it may be located in the dash, or in the engine bay. As this particular engine is OBDII, there are particular laws the manufacturer must follow in mounting the plug, and it will most probably be located under or near the steering wheel.

< http://en.wikipedia.org/wiki/On-board_diagnostics#OBD-II_Diagnostic_connector > This link shows information on the OBDII connector and laws surrounding it.

Next we plugged in our scan tool and asked our tutor to introduce a fault into the system. We then turned on the Scan tool and entered the required data for it to begin diagnosis. The fault code came up as PO120. After searching the workshop manual, I found the fault was coming from the TPS. The first test I did was a visual check. I checked rigidness and condition of plugs, I looked for nicks, breaks or corrosion in the wire, and checked the condition of the sensor itself. I then checked voltage supply to the sensor. My multimeter showed 0v. I then reported this to the tutor and as the fault wasn't anywhere I could repair, he switched the fault switch back on and I carried on. To clear the codes, I pressed the "clear codes" button on the Scan Tool, and turned the ignition on then off again. The Scan Tool showed no codes.