Diagnostics expert, Frank Massey has spoken to AutoCar about the issues blighting independent garages when it comes to correctly diagnosing vehicle faults.
During his interview, Frank explained how oscilloscopes can provide the gateway to looking at the cause, rather than symptom of the fault in question.
He said: “A scan tool, or code reader, shows you the symptoms of a problem but an oscilloscope shows you its cause.
“The former gives a tech only half the story; the oscilloscope reveals the profile of the signal and its flow.
“The road map to a fault”
“It’s the road map to a fault.
“Imagine a tiny box. If all’s well within it – in other words, if a signal’s profile doesn’t stray outside it – no error code is triggered.
“But what if the signal’s extremes are teetering on its edge?
“It may be just enough to cause a problem but not to generate an error code.”
Frank went on to explain how the ECU constantly struggles to keep signals within these millions of tiny boxes, in the process generating ‘correction values’.
Identify and understand these, he explained, and you’ll find out what’s really going wrong.
Referring to a recent example, a customer’s four-year-old Audi A6 2.0 TDI was suffering with a long-running problem after the main dealer who’d been trying to fix the car had been misled by an error code and, running out of options, told the customer it needed a new selective catalytic reduction (SCR) system.
However, Frank said: “By examining signal strengths and flows, and the wider environment the SCR was operating in, we discovered it was the exhaust gas recirculation cooler that was at fault.
“Basically, it had an air block.”
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