December/January 2022

DECEMBER/JANUARY 2022 AFTERMARKET 37 www.aftermarketonline.net Above: Fig 1. Right: Fig. 3 been received by the module, as is now commonplace on modern vehicles. Multiple modules use wheel speed data, not just the ABS system itself, so this is why they log faults for other modules. I didn’t have any modules failing to communicate so this indicated that it was more than unlikely a module was at fault. However, I still had the dashboard issue present which was a permanent fault and it could not be discounted. Intrigue What did intrigue me however was why the mileage and trip displays were just reading “----" and not numbers? What could cause this and why was it happening? Could it be a faulty instrument panel or perhaps a body control module issue? As in most cases now, it stores the main data for the vehicle including total mileage covered. I didn’t have any real fault codes to use as clues so I decided to focus on the ABS fault first, fix it, then go from there. It can be really easy with faults like this to go down a rabbit hole trying to find an issue that is not there. Experience has taught me to fix what you know is wrong first then reassess and then attack the faults which remain. We knew the ABS system had a fault so we fix it first then see what the dashboard displays. My next step was to access live data and do some checks dynamically before I went any further. Displaying all four-wheel speeds showed a problem straight away. With the vehicle sitting stationary in the workshop, the left front wheel speed read 255km/h, which you wouldn’t expect. Meanwhile, the other three read 0, which you would expect as the vehicle wasn’t moving. Experience has taught me that on most Ford vehicles, not all though, 255km/h indicates a circuit problem, whether it be a Above: Fig 2. sensor issue or wiring. I knew I had to do some tests to establish the cause of the fault. Detached I then removed the left front wheel to test the wiring and ABS sensor and a visual inspection found the cause of the ABS fault (see Fig.3). For some reason the wiring loom for the sensor had detached from the securing clip, which can also be seen in the picture, and had allowed the wiring to rub against the tyre and wear through to the point that it was now completely broken and became open circuit. I then cut back the insulation and repaired the wiring and checked live data before completing the repair. It is important to confirm the repair first before you fully assemble the vehicle only to find an issue still exists. Been there, done that and got the t-shirt. I now had all four sensors reading 0 km/h. Spinning the left front wheel while on the ramp showed the sensor to respond and read a wheel speed, so the wiring was then insulated correctly. Knowing the ABS fault was repaired, the vehicle was then reassembled, but this time the wiring loom was secured away from the wheel and tyre. I then cleared all the fault codes in the vehicle and rechecked the customer’s complaint. I found that the car now had no faults stored in any module and the mileage and trip readings displayed correctly. A road test confirmed we also had a working speedometer and a final global fault code scan on return to the workshop showed no fault codes, so the vehicle was fixed. What can be learned from this job? As I said earlier, it would have been very easy indeed to start chasing the mileage/trip display fault. This could possibly condemn the dashboard. Alternatively, I could have ended up removing it and sending it off for testing, only to then be told it had no faults and then be left wondering where to go next. Fix what you know is wrong first, then reassess the situation; Diagnostic work is much easier when you apply methodical thinking and work to a test plan specific to the vehicle and its faults, like I have mentioned in many articles before. Experience has taught me to fix what you know is wrong first then reassess and then attack the faults which remain ”