Scan Tool Diagnostics
Using a Scan Tool that communicates to the engine you want to test.)
Warning: Be careful working around engines and exercise caution to avoid injury.
1. Scan Tool Data
1.1 Our vehicle is appropriate for the scan tool.
1.2 Connect the scanner, power it on, follow the instructions and input the correct vehicle information it asks for so you can view the data.
1.3 Find the data for the information listed on the next page. Turn engine on to idle. Fill in the letters used to label the information and the value of that data. (For example, engine load information may be found under MAP, with a value of 3.6, listed in volts) Note: not all vehicles will support all information, just find as much as you can. If the engine won’t run, input the information with the key on, engine off.
Type of information (PID = Parameter Identification) | Letters to describe it E.g. TPS | Value of data | Units for data E.g. volts |
Engine Load (how much air comes in) | MAP | 0.95 | volts |
Engine RPM | RPM | 900 | RPM |
Throttle angle | 0 | Degrees | |
Engine coolant temperature | TAW | 0.44 | volts |
Fuel Injection opening pulse | ING | 3.3 | ms |
Transmission select position | No | switch | |
Vehicle Speed | 0 | KM/H | |
Oxygen sensor(s) | 02 | Lean | Good |
Fuel Trim | N/A | ||
Idle control | ISC | ON | Switch |
Power steering condition | N/A | ||
Air conditioning condition | OFF | Switch | |
Exhaust Gas Recirculation (EGR) | N/A | ||
Fuel Evap or Purge condition | N/A | ||
Malfunction Indicator Light (MIL) | N/A | ||
Barometric Pressure | N/A | ||
Sark Advance | 10 | degrees |
2 Trouble Codes or Fault Codes
2.1 Found where the Codes are listed
2.2 Recorded any codes, and what system and condition they describe in the chart below (Example: might be code number 21, for Throttle Position Sensor, signal voltage too low)
Code number | System affected | Condition described |
None | None | None |
3.1 Created a fault under the hood.
4 Record New Codes
4.1 Look up the codes now in the scan tool
Code number | System affected | Condition described |
31 | MAP | We unplugged it. |
5 Find What Data Has Changed
5.1 We Looked through the scan tool data to see what PIDs (Parameter Identification of system voltages) have changed. Which readings don’t make sense or don’t read what you would expect. Concentrate on the PIDs related to the codes.
5.2 I Recorded the PIDs that have changed below:
Type of information (PID = Parameter Identification) | Letters to describe it | Value of data | Units for data |
Engine Speed | RPM | 720 | RPM |
Ignition Timing | IGN | 5 | Degrees |
Oxeygen sensor | 02 | Rich | mixture |
Idle Control | ISC | 117 | Steps |
6 Visual Inspection to find fault
6.1 Did a visual inspection under the hood to find where the problem was. Used information from the code to know where to look for the problem.
The problem was found by looking at the MAP sensor and noticing it was unplugged.
7 Repair fault
7.1 Plugged back in the connector
8 Recheck Data PIDs
8.1 I Rechecked the data with the scan tool
8.2 And recorded the voltages for the PIDs related to the problem, to confirm they are back to normal
Type of information (PID = Parameter Identification) | Letters to describe it | Value of data | Units for data |
Engine Speed | RPM | 900 | RPM |
Ignition Timing | IGN | 10 | Degrees |
Oxeygen sensor | 02 | lean | mixture |
Idle Control | ISC | on | Steps |
9 TO Clear the Codes I disconnected the battery for 30 seconds leaving the key off.
10 I then Rechecked for codes and none were found
11 Discuss the importance of live data when fault finding
12 Live data is very useful as faults can be found whilst the car is being operated or driven. This can reveal faults and problems that only occur while the engine is under load and all the systems operating.
13 Explain the need for parameters when checking live data
Live data should be compared against the specifications or parameters for the car. If the live data is outside these parameters, then there must be a fault with that system.
14 Discuss how a scan tool can aid you when fault finding
The scan tool makes finding faults very easy, although you must use both fault codes and live data to correctly diagnose any problems with the vehicle. A scan tool can also diagnose many other systems within the vehicle rather than just the engine.
