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Using OBD Diagnostics

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Easy Guide to Scanning
OBD2 - Fuel Pressure
OBD2 - Faulty HO2S
OBD2 - Bad Cats
OBD2 - Lambda
OBD2 - Bad MAF
OBD2 - Poor running
OBD2 - Poor Running TPS
OBD2 - Refresh Rate


Setting up the OBD-2 Diagnostics

The mechanics of using the OBD2 interface to read the EECV PCM is described very well in the article OBD2 Engine Mgt. The actual reading from the PCM will depend on several factors, including the speed of the processor of the laptop or PC, and the transfer speed of the serial connector.

First of all check out the Help File, and check each point carefully in the Trouble Shooting page. There are some serial port issues which are worth checking. Then go to Options - Gateway - Protocol. Make sure that the Ford PWM option is ticked, and that the speed is set at about 120. On the right check that timeouts is at 2 or 4, and I use the Auto Reconnect option so that if it does fail it automatically logs in again. Check the Manuf. Enhanced login in order to use the Ford specific readings.

On the Interface tab, check that the baud rate is at 57.6, the Blue Route option is ticked, the Use Direct ISO and Use Fast Tricom options are all ticked.
Make sure the plug is pushed in securely, and don't jog it with your knee. I have connected for as long as twenty minutes and as little as 2 minutes, but I have found the above settings work well.

After connection check the log on the Info page - this will show how the connection went. When making the first connections, just switch on the ignition rather than running the engine to start with so that the bus has more time to respond to requests. You can change the PWM speed to 130 and increase the timeouts until you start to get responses. It's all a matter of fine tuning.

But what can OBD do for us?

Scan Files
Unless you specifically tell the program not to do so, the OBD2 interface will automatically log every connection. When you select an address in the PCM, it will continue to send the data back to the laptop where it is recorded. This takes time, of course, and the more addresses you have selected the greater will be the time lapse between each reading from any one sensor.

Neither do we have a list of correct or acceptable readings - we have to build up our own experience of what the data should be, so from the start I scanned the EECV on the standard OBD addresses, and then checked the Enhanced (Ford Specific) addresses. From this I have a list of all the sensors from which the OBD2 can obtain readings.

In successive scans I took short readings from each sensor before cancelling the connection and moving on to the next. In this way I hope I have a sample of most of the addresses when the PCM is functioning correctly. To assist I have zipped some files and you can use the free OBD-2 software to examine for yourself.

Each zip file contains three files for each scan, and each must be in the same folder when you attempt to read them. Simply unzip the files into a folder called 'Log' in the OBD2 folder. The scans will then show up when you select 'replay' on the OBD software. Double clicking will open the file and a little radio control will appear. Select Play and lower the playback speed from 100 to about 35 and this will give you more time to watch the readings. On the files marked as Enhanced open the enhanced window from the top menu and wait until you see the readings coming through. Data can be can be obtained from the standard OBD connections and the Enhanced at the same time.

File Name  Comment Standard OBD Data Enhanced Ford Data Monitors operation of the EGR   CCS EGRVR EPC GEAR LOAD Standard OBD operation LOAD RPM ECT MPH MAF O2S Monitors Enh. functions, including the Torque Converter Clutch  (TCC)    EGRVR GEAR TCC EPC Monitors enhanced first, then standard LOAD MPH RPM GEAR VSS Urban journey   MAF TPS IAT O2S MPH Lists all Enhanced   Samples all sensors

Analysing Enhanced Files

Of course, one disappointment of the software is that it does not display the Enhanced readings on the dashboard. With these readings, it is simple to export the data into a PRN file which is then inputted into Excel. Opening Excel and selecting all files, the scan file appears as the same filename, but with a PRN. Excel automatically adopts the Import strategy, asking for the type of file it should adopt. Select Delimited, the Comma Separated, and the data will appear as an Excel text sheet. Save it immediately as an Excel worksheet.

The data appears in columns, with the headers showing all the address headings along the first row. Insert a split under the first row, and the headings remain where they are for reference as you scan downwards.

Each reading has the electronic time beside it, so these columns can be dragged across from the right to hide the times, leaving just one time on the left margin. Rows at the beginning of the sheet will be blank until readings have been received, so they may be deleted until the bulk of the data is visible. I carried out this process on Scan13, and the zipped Excel Worksheet can be downloaded here.

Using the data by selecting the title first and then the data columns using the CTRL key, calling up the Chart Wizard and ordering the data sets in Columns, one can plot different results. On the right is the Torque Converter Clutch expressed in percentage engaged, with the VSS (Vehicle Speed) sensor beneath it. (This journey recorded on a German Autobahn)

Data sets connected only by inference can be plotted against one another : below, taken from Scan 4, the calculated engine load expressed as a percentage is plotted against the vehicle speed .

Using the data in this way can provide a powerful insight into the way that the vehicle is performing.

One last point just occurred to me. using the OBD2 from stationary and logging the run, one could do a 0-60 dash and use the OBD2 timer to calculate the time taken!

Use the example scans on the left to see an example of failed HO2S sensors, catalyst tests and poor running.

NOTE: If you purchase the PWM/ISO combi lead option, you will be able to communicate with the ABS module as well, read ABS trouble codes and clear them yourself. 





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