Automotive scan tools have revolutionized vehicle diagnostics and repair since their inception in the 1980s with GM’s Assembly Line Diagnostic Link (ALDL). Initially designed for pre-delivery checks, these tools quickly became indispensable for service professionals seeking to understand a vehicle’s onboard computer systems. Today’s automotive scan tools offer a wide array of service functions, far beyond basic code reading. Understanding these capabilities is crucial for technicians and car enthusiasts alike.
Before diving into the advanced service functions of modern scan tools, it’s essential to remember the fundamentals. Mechanical issues, fuel delivery problems, or ignition faults can all trigger diagnostic trouble codes (DTCs) and other data points accessible via scan tools. Always begin with a thorough visual inspection, checking vacuum hoses, battery connections, wiring, and ground points. This foundational step ensures that you’re not misinterpreting scan tool data due to simple, overlooked problems.
Diagnostic Trouble Code (DTC) Retrieval: The Starting Point
Retrieving Diagnostic Trouble Codes (DTCs) remains the most frequently used function of automotive scan tools. Often, a lit Malfunction Indicator Lamp (MIL), commonly known as the “check engine light,” prompts technicians to connect a scan tool. Furthermore, with increasing adoption of OBD II emission checks in many regions, DTC reading has become even more vital for compliance and repair verification.
However, it’s crucial to understand that DTCs are merely indicators, not definitive diagnoses. They pinpoint a problematic area but not the precise cause. Think of them as starting points in your diagnostic journey. When selecting a scan tool, verify the range of codes it can display. Some basic tools might only show generic OBD II codes, lacking the detailed, manufacturer-specific information needed for accurate and efficient repairs.
Serial Data and Parameter Identification (PIDs): Real-Time Insights
Vehicle system malfunctions don’t always trigger DTCs. This is where the real-time data streaming capabilities of scan tools become invaluable. Serial data, also known as Parameter Identification Data (PIDs), allows you to monitor live sensor readings and system parameters directly from the vehicle’s control modules, primarily the Powertrain Control Module (PCM).
For instance, a vehicle might exhibit driveability issues without setting any fault codes. By examining PIDs, you can observe sensor values – such as engine temperature, oxygen sensor readings, or throttle position – and assess if they fall within expected ranges. This real-time data stream offers a deeper understanding of system operation, helping identify subtle anomalies that wouldn’t necessarily trigger a DTC. Like DTCs, PIDs provide crucial pieces of the diagnostic puzzle, guiding you towards the root cause of the problem.
Mode 6 Data: Uncovering Potential Issues Before They Escalate
Mode 6 data represents an advanced OBD II diagnostic mode focused on onboard monitoring of test results for systems not continuously monitored. This function provides live, unrecorded data, offering a glimpse into real-time system performance metrics like ignition misfires and fuel control effectiveness.
The power of Mode 6 lies in its ability to reveal intermittent faults or developing problems before they become severe enough to trigger a DTC or illuminate the MIL. By accessing Mode 6 data, technicians can proactively identify and address potential issues, preventing breakdowns and costly repairs down the line. However, Mode 6 availability varies across scan tools and vehicle systems. When considering a scan tool purchase, inquire about its Mode 6 capabilities, especially as automakers increasingly leverage this functionality in newer models.
Actuator Tests: Verifying Component Functionality
Many modern automotive scan tools offer actuator tests, enabling technicians to directly command specific components to activate and verify their operation. The scan tool communicates with the PCM, instructing it to trigger actuators like relays, solenoids, fuel pumps, or cooling fans. This allows for direct functional testing of these components.
Chrysler vehicles, historically, have prominently featured Actuator Test Mode (ATM) for component checks. When evaluating scan tools, confirm their actuator test capabilities, particularly for the vehicle makes you frequently service. Actuator tests provide definitive confirmation of component functionality, isolating problems and saving diagnostic time. Remember, actuator tests, like other scan tool functions, are part of a comprehensive diagnostic approach.
Bi-Directional Communication: Interacting with Vehicle Systems
Most contemporary scan tools provide bi-directional communication, allowing interaction with various onboard vehicle systems beyond just reading data. This two-way communication empowers technicians to send commands and receive responses from modules controlling body systems, Controller Area Networks (CAN), infotainment, fuel management, Anti-lock Braking Systems (ABS), transmission control, and more.
Bi-directional controls can include functions like activating ABS solenoids, commanding fuel pump relays, or even adjusting idle speed (depending on vehicle manufacturer implementation). This interactive capability expands diagnostic possibilities, enabling active testing and system verification beyond passive data observation.
Signal Substitution: Simulating Sensor Inputs for System Analysis
Certain advanced scan tools offer signal substitution, a powerful feature for system analysis. This function allows technicians to temporarily override sensor inputs to the PCM with manually set values. By “substituting” a known good signal, you can assess the PCM’s response and isolate sensor-related issues.
For example, a faulty Vehicle Speed Sensor (VSS) can impact multiple systems including cruise control, speedometer operation, and transmission shifting. By using signal substitution to simulate different speed signals, you can quickly determine if the issue lies with the VSS itself or within the systems that rely on its input. This feature streamlines troubleshooting complex, interconnected systems.
Onboard Service Information: Integrated Repair Resources
Many modern scan tools integrate onboard service information, providing quick access to repair resources directly within the tool interface. This can include technical service bulletins (TSBs) related to specific DTCs, wiring diagrams, component locations, and repair procedures.
While not a replacement for comprehensive online service information systems, onboard data can be a significant time-saver during diagnosis and repair. Quickly checking for relevant TSBs or accessing wiring schematics directly on the scan tool can expedite the repair process and ensure accurate procedures are followed.
Choosing the Right Automotive Scan Tool: Matching Functions to Your Needs
Selecting the “best” automotive scan tool depends entirely on your specific requirements. Do you primarily work on domestic, Asian, or European vehicles? Are you a professional technician or a dedicated DIYer? Consider the vehicle makes and models you service most frequently, and anticipate future needs.
Explore different types of scan tools: aftermarket vs. Original Equipment (OE), handheld vs. PC-based. Discuss options with fellow technicians and equipment suppliers. Crucially, try out scan tools hands-on before committing to a purchase. In some cases, owning multiple specialized scan tools may be necessary to effectively address the diverse range of vehicles encountered in a modern repair shop.
Ultimately, remember that even the most advanced automotive scan tool is just one tool in your diagnostic arsenal. While onboard diagnostics are incredibly helpful, they are not a substitute for a solid understanding of vehicle systems, proper testing procedures, and the use of other diagnostic equipment when needed. A comprehensive approach, combining scan tool proficiency with fundamental diagnostic skills, is the key to efficient and accurate automotive repair.
