16 years ago, there was no uniformity in how diagnostic trouble codes were displayed or retrieved from vehicles. Each manufacturer developed their own dedicated systems, with some having one or two digit codes while others had more comprehensive three and four-digit coding systems. In many cases, DTCs in early systems could be displayed by connecting a LED tester or jump wire between two pins in the data link connector (DLC), then counting the LED or malfunction indicator lamp (MIL) flashes. This lack of consistency between manufacturers made diagnostics more difficult and time-consuming for technicians.
Today we seem to have it easy. There are over 50 DTC readers on the market that help us diagnose the faults in a vehicle. Although code readers are helpful tools, DTCs can still be difficult to understand. DTCs often indicate the area of a fault, rather than the fault itself. Many technicians have made the time-consuming and expensive mistake of simply replacing components because a particular DTC was identified; only to find that the problem persists and the same code is being displayed by the code reader.
For example, a code reader has identified the trouble code P1102, which typically indicates a mass air flow (MAF) sensor range or performance problem. There are several items that should be checked before any parts are replaced. Firstly, the readings from the MAF, then the integrity of the wiring should be checked. In this case, they are both ok, so an air leak check needs to be carried out. Eventually, an air leak was found by the technician that caused the MAF sensor reading to fall out of sync with the ECM and generated the fault code. If the MAF sensor had been replaced at the first sign of trouble, the workshop or the customer could be a few hundred pounds ‘out of pocket’ and the fault would still be present.
It’s important to understand that DTCs will not always diagnose direct faults. Instead, they often provide systematic clues that require a combination of technical knowledge and investigation to solve.
There are over 79,000 diagnostic trouble codes available in Autodata’s dedicated DTC module. It provides technicians with everything from basic diagnostic information such as connecting to and accessing the DLC, to identifying the system(s) associated with each diagnostic trouble code and informing technicians what the faults are likely to be.
