Diagnostic tips in practice: WARNING LIGHT ISSUE
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Diagnostic tips in practice: WARNING LIGHT ISSUE

Discover in this study case some diagnostic tips related to warning light problems, the causes and the solutions.


The vehicle was brought to the workshop with the ABS warning light on. The owner reported that although the vehicle seemed to be driving normally, the brake warning light was permanently on. The engine warning light had remained on for a few days some weeks previously, but had subsequently gone out.


  • Step 1: The technician connected a scan tool to the diagnostic connector and found three stored fault codes: P1536, P2562, P1497. The fault codes were read out before being cleared. The warning light went out. The vehicle was road-tested. During the test, the ABS warning light came on again
  • Step 2: The technician logged into HaynesPro’s WorkshopData and quickly selected the correct vehicle using its registration number. The scan tool was reconnected and this time only the P1536 code was present. The fault code was entered into the search box and returned ‘Brake pedal travel sensor: Coherence’. VESA™ (Vehicle Electronics Smart Assistant) gave two suggestions: 1) to test the brake pedal switch, and 2) to refer to a possible known fix found in a SmartCASE bulletin. 
  • Step 3: Following the advice in the bulletin and the suggested diagnostic tests offered by VESA, the technician tested the brake pedal switch wiring. No fault was found. 
  • Step 4: Continuing to follow advice given in the bulletin, the technician renewed the brake pedal switch. The repair time given by the OEM was 0.20 hours. The fault code was cleared, and the vehicle road-tested again. This time, the ABS warning light remained off. Once back in the workshop, the technician reconnected the scan tool and noted that no-fault codes had been stored.
  • Step 5: With the brake fault fi xed, the technician now wanted to investigate the other fault codes retrieved when the scan tool was first connected. As before, the technician entered the codes P2562, P1497 into the search box (WorkshopData allows seven fault codes to be searched simultaneously). As before, VESA returned the fault descriptions, suggested diagnostic tests and a relevant Technical Service Bulletin (SmartFIX). The bulletin advised that the cause might be the turbocharger pressure regulator pneumatic control. As the fault codes had not re-occurred, no further diagnosis was necessary. As a precaution, this additional advisory information was given to the owner when the vehicle was returned. The proactive, predictive diagnosis was welcomed by the satisfied customer, who stated that they would definitely bring the vehicle back should the intermittent fault return.

You can try out all the features of HaynesPro WorkshopData and discover more about doing a full diagnostic of warning light problems for 7 days free of charge and without obligation:


One comment

  1. Michael Atkinson

    Hi I am currently trying out hanyes Pro, but do not have full access? Can you help

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