Page 44 - Australasian Paint & Panel May-June 2021

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Diagnostics
PAINT&PANEL MAY / JUNE 2021 WWW.PAINTANDPANEL.COM.AU
DON’T DASH OFF YOUR SCANS
RELYING ON DASHBOARD INDICATORS AS
an information source of what is going on in a car is nothing short of dangerous, as is the misconception that only really new ve- hicles need pre and post repair scans.
Over in the US back in 2017 a Montana collision repairer kept statistics on his three shops’ repair orders to examine the necessity of pre- and post-repair scanning and whether the dash light can serve as an indicator of fault codes.
Their findings from scanning more than 200 vehicles bear out what OEMs have been saying: Vehicles require scan- ning, and the dash light is for custom- ers, not auto repair professionals.
Here are some study highlights:
• Only about 14 percent of the 216 vehicles McDonnell’s staff scanned actually had a dash light on when it came into the shop. About half of these dash lights were Trye Pressure Monitor and or maintenance
lights not related to the repair.
• About 80 percent of the vehicles with- out a dash light showing posted at least one fault code when scanned prior to
the repair. Some threw as many as 13. • Vehicles with fault codes but no dash lights encountered at the shop reached as far back as 2006 and into the 2017 model year, OEMs say this condition can extend at least as far as
the OBD-II standard in 1996.
• Post-repair scans found numerous ad- ditional faults, which is not surprising as the repair process itself generates fault codes. The record appears to have been claimed by a 2015 GMC K1500 Yukon, which amazingly came in with zero fault codes but had 107
following an extensive repair.
• 49 out of 50 cars came back with codes related to the repair or collision. At that point, the McDonnell Group de- cided to check dash light data as well and collect subsequent findings in a spread- sheet. Technicians found that a vehicle typically needed a “pretty hard hit” before
dash lights would appear.
McDonnell said his technicians “live
and die by the prescan” and the details it provides them about modules and
parts requiring attention. If you waited until the end of the repair to scan the car and found, “we have to replace this, this and this,” and start tearing the car back apart to do so, “who’s going to pay us to do that?” he said.
So, to reiterate a few dashboard lights aren’t going to tell you everything wrong with a car packed with tens of millions of lines of code and dozens of sensors.
Dave Luehr of Elite Bodyshop Solutions ran a two hour webinar in April with Mike Anderson of Collision Advice and diagnostic guru Jake Rodenroth of asTech which is available free at elitebodyshop- solutions.com. In this webinar they thor- oughly explain DTCs (Diagnostic Trouble Codes) what they are and how they are, or importantly aren’t generated.
Each DTC can be in one of four states – clear, pending, active or previously ac- tive. Certain conditions have to be expe- rienced by the vehicle before it will set a DTC. One of these maybe speed, a vehicle may need to trigger a specific speed – that is common for Tyre Pressure Control, Intelligent Cruise Control, ABS, Traction Control and Blind Spot Monitors. If a ve- hicle has been in an accident and is towed in it won’t have achieved those designat- ed speeds. Another one is key cycle, the key may not have been turned on or off enough times to trigger the DTC and that applies to cars driven in after an accident. Rodenroth points out that cars don’t know they are in a bodyshop, they just know that someone disconnected a sen- sor or a control module – like tail lights or door handles being removed.
Anderson says a test drive post repair is essential to ensure there are no DTCs which could have been triggered by the repair. Communication failures are the most common DTC in the collision repair shop as so many sensors or parts that modules commonly ‘talk to’ are removed.
There is a wealth of training available in the marketplace to ensure that if you are undertaking in-house scans that you can interpret the data generated. There are also diagnostic tools which an ‘inter- preter’ service where all you have to do is undertake the scan and they will tell you what the data means.