Finding the root cause

20 August 2014  

By Vince Thorpe, Diagnostic Product Specialist at Snap-on

When electronic control units (ECU’s) first appeared on motor vehicles, it was widely believed that they would provide technicians with the root cause of a fault, informing them of the problem component that required replacement. The reality is that this has never really happened, and as vehicles become more complex, so do the fault codes they produce. Now, the information produced by the ECU is a guide only -the fault code is generally an effect and is not the actual cause of a problem. Furthermore, vehicles with a recurring problem may not have a fault code stored in the ECU at all. Information and expert guidance are the tools needed to repair these problems but knowing all the possible glitches and faults across the ranges of say 40 different vehicle manufacturers is just not possible and with technology constantly evolving, this undoubtedly will continue to be a major challenge.

Beyond fault codes

To help technicians overcome this issue, diagnostic equipment manufacturers such as Snap-on offer scan tools with functionality that extends well beyond retrieving fault codes from the ECU, providing detailed step-by-step information on how to get to the cause of a fault and fix it. From the workshop owner’s perspective, it’s also worth ensuring that technicians are making the most of the diagnostic tools that have already been invested in and the functionality the technicians may well already have at their fingertips.

For example, Snap-on scan tools from the Solus Ultra model and above have a ‘Troubleshooter’, function that provides vehicle-specific help, rather like having a master technician working alongside but built in to the scan tool. All that’s needed is for the technician to select the code extracted from the vehicle by the scan tool and then use the Troubleshooter to identify the likely cause of the fault, as mass produced vehicles typically produce the same faults consistently. For example, if ‘Turbo Pressure Positive Deviation’ is reported, the likely cause is an ECU software problem requiring a dealer update. If no fault codes are reported, Troubleshooter’s ‘Symptom Tips’ section provides the common faults related to the specific vehicle being diagnosed, such as poor starting or lack of acceleration. This information alone can give technicians a better understanding and save time and money when it comes to finding those obscure faults.

Reviewing data

If there’s a problem, but no fault codes are being reported, live data from the ECU can be reviewed to see each line of data and identify the component operating outside its normal range, but without a reference this can also be a challenge. To get round this, Troubleshooter’s ‘Parameter Definitions’ section provides a list of all the live data that is coming from the vehicle’s ECU, technicians can then select any parameter to see the operating range that particular line of data should be operating within. Along with vehicle specific ‘Component Locations’ and ‘Component Testing’, Troubleshooter provides technicians with the information at their fingertips needed to identify and repair the vehicle.

After finding and repairing the fault, most vehicles now require a relearn/reset or configuration carried out to complete the repair. This is found in Troubleshooter’s ‘Final Procedure’s section, with step-by-step assistance to carry out manufacturer or vehicle specific procedures to complete the repair. All procedures are engineered to be safe, so no damage will occur to any vehicles systems.

www1.snapon.com/diagnostics/uk