Scan tools
Last Updated on July 22, 2024 by Mutiara
A scan tool is one of the most important diagnostic tools to have for working on modern vehicles. A scan tool, code reader, or scanner software provides access to the vehicle’s onboard diagnostics in the event that a CEL (Check Engine Light) comes on to find out what’s wrong. The scan tool allows you to see diagnostic information and error codes.
Reading Codes
Diagnostic trouble codes can be obtained manually by jumping or grounding certain terminals on the diagnostic connector on the majority of 1995 and older American vehicles that are pre ODB2. Upon grounding the proper connections, the PCM (Power Control Module) goes into a self-diagnostic display mode, and flashes code sequences via the CEL (Check Engine Light) or as it is also common referred to as the MIL (Malfunction Indicator Lamp). By looking up the codes on various online references, one can find out why the indicator is on.
The two main downsides with manual flash codes is that counting the codes can be difficult and that they stopped being used on the majority vehicles manufactured after 1996. Code sequences are usually done through a combination of short and flashes that represent double digit codes. Sometimes distinguishing different codes from one another can be difficult if the vehicle has multiple error codes. Hence the favored method of reading codes on older vehicles is through the use of a scan tool or code reader.
Vehicles manufactured on 1996 and after, however, do not have any manual flash codes. Accessing codes on OBD-2 equipped cars requires a code reader or scan tool.
Coder readers
Actron PocketScan code reader
A Code Reader is an affordable entry level diagnostic tool. It is able to access and display codes from the vehicle’s computer. While the least expensive models only display the code, more expensive units will usually provide an explanation. Some models even include multiple languages and allow the explanations to be displayed in English, Spanish, or French. The average cost of a code reader is $ 50, they are available in any auto parts store, and are sometimes even stocked by large department stores such as Walmart.
One of the most popular uses a code reader is usually sought after is it’s ability to clear codes and turn off the CEL. Certain models can also show the “ready” status of different OBD-2 monitors. A monitor is in ready status once it has finished the self-check process error free. However, since a code reader can only read and clear codes, it is not a scan tool. It cannot display anything other than system operating information. Reading sensor and various system data requires a scanner software or a scan tool.
One important factor to consider is that a fault code doesn’t necessarily reveal which part needs to be changed. A code’s purpose is to report the detection of a fault, not it’s cause. It serves as a starting point for additional diagnosis. Very often this misunderstanding causes people to assume that a cheap code reader is all that is required for diagnosis and repair of the vehicle.
Another common misconception is that any code can be read by any code reader. While they’re guaranteed to read universal P0 OBD-2 codes, some units will fail to display manufacturer specific codes, which are P1 “enhanced codes”. Even if a unit does read the P1 codes, it may still be limited by types of vehicles, such as domestic, and fail to display codes from European or Asian vehicles.
Prior to purchasing a unit, you should check which vehicle years the specific model is able to access. The majority of code readers on the market are for 1996 and newer OBD-2 vehicles, with a standard 16-pin interface. The type of interface is specific to OBD-2, and usually means the code reader cannot access OBD-1 vehicles due to a different connector. Vehicle specific code readers are available for certain older Chrysler, Ford, and GM applications. The same goes for import vehicles such as Audi, BMW, Mercedes, and even the Mini.
Due to the ever growing lists of DTCs and system data which increases every year, code readers and scan tools alike are prone to becoming obsolete on newer vehicles. A tool made just a year before may be incompatible with the next year’s vehicles. Since tools can become outdated quickly, many units are equipped with ways to upgrade the software through the means of cartridges, plug-ins, or downloads from the manufacturer’s website. When browsing for a used code reader on sites like eBay, it’s a good idea to make sure the tool is either compatible with your vehicle or has the option of being updated online.
Scan tools
Actron CP9175 code scan tool
A full featured scan tool is necessary for a more advanced diagnosis of modern vehicles. There are two types of scan tools. The common scan tool available in most stores for DIY mechanics is usually capable of displaying system data and sensor values, but it is not able to perform various system self-tests. On the other hand a professional scan tool which is much more expensive, is able to perform many system self-tests such as the following:
- A/C compressor clutch
- Cooling fans
- EGR regulator
- EVAP leak test
- EVAP purge controls
- Fuel injectors
- Fuel pump
- Idle speed control motor or (IAC) idle air control valve
Such tests require proper software and most importantly the capability to communicate bidirectionally or two-way with the car’s computer in order to access and carry out such diagnostics.
Most common entry level scan tools can be obtained for less than $ 200. Their capabilities range from reading and clearing codes, reading the status of various OBD-2 system monitors, and reading basic operating data such as:
- Airflow
- Coolant temperature
- Loop status (open or closed)
- O2 (Oxygen) sensor outputs
- TPS (Throttle Position Sensor)
- Fuel trim values
While domestic vehicle makes such as Ford, GM, and Chrysler are always supported by most entry level scan tools, some will require additional software for European and/or Asian applications.
Since the majority of entry scan tools which are sold in auto parts stores are made for DIY mechanics, bidirectional communication support is usually not included for liability purposes. Compared to professional level scan tools they’ll also usually have a smaller number of PIDs (Performance Information Data). This means they’ll contain less data on things such as switch status, sensor values, and etc. than a professional level or factory scan tool.
Professional scan tools
Innova CAN compliant scan tool
By comparison, the advanced aftermarket scan tools can perform the same tasks as any OEM factory scan tool. Professional scan tools can display and access most PIDs, if not all, so long as they have the proper software. They are also capable of running msot of the OEM self-tests.
Most professional scan tools will include a better LCD display, that is larger and includes color graphics. Some tools will have the ability to display a multi-channel scope, allowing data to be shown in either wave or graph form. A scope is especially helpful when it comes to observing certain problems that occur too fast to spot in a numerical data readout. Another feature that many scan tools contain is the ability to record data during vehicle operation, so that it can be analyzed for later. An add-on which if often used by various inspection agencies is a 5-gas emissions analyzer, which can be beneficial in tracing various details of the burn cycle otherwise unknown during a typical diagnosis.
To keep up with new developments in vehicular computer software and configuration, many professional units will have the option to flash reprogram the PCM. The updated software can help bring the engine up to proper operation and correct emissions issues. Certain vehicles require flashing the PCM if it is replaced. If the tool lacks support to flash the PCM, then a J2534-compliant pass-through tool can can accomplish the task by providing an interface between a personal computer and the PCM in a vehicle.
A vendor’s claims of the vehicles their product or software covers can be misleading. Always perform research on the desired unit to make sure it has all of the features you want. Following is a list of 3 common downfalls that you should watch out for:
- Claims of covering a vast amount of vehicles, however the actual support will only for basic OBD-2 information. Lacking support for even the enhanced codes for the vehicles listed.
- A unit may have complete support for all OBD-2 codes, yet lack any other codes that are not directly related to the engine or the powertrain. Such codes as those used for ABS or air bags.
- Limited diagnostics and lack of all the factory tests and procedures.
OEM vs aftermarket
While OEM factory scan tools may be complete when it comes to accessing everything in the vehicle’s computer system, they tend to be far more expensive than most aftermarket scan tools. However certain top end aftermarket scan tools can also cost thousands of dollars. A price ranging from $ 5,000 to $ 12,000 is not uncommon for OEM scan tools.
Some examples of OEM scan tools is the NGS (New Generation Star) for Ford, Lincoln, and Mercury vehicles. Another is Tech II for GM, and the DRB III for Chrysler vehicles. Though generally these scanners are becoming obsolete due to superior computer software based scanners in dealerships. As a result, some can be found used for a decent price on eBay or craigslist.
Some benefits of having an OEM scanner are:
- Full access to all diagnostic fault codes, which includes OBD-2 and enhanced codes.
- Capability to run all on-board self-tests, rather than being limited to emissions and engine performance. Some of these include:
- ABS module
- Air bag module
- Body control module
- Climate control module
- Suspension module
- The ability to initiate or reset a module that was replaced. Certain vehicles require this to make the module work correctly.
- In certain applications, the ability to initiate a special relearning procedure for replaced modules that are not available in any aftermarket scan tools.
A major downfall of OEM scan tools is the narrow list of vehicles they’ll generally work on, since they were designed for a specific application. This is why they are more suited for use in dealerships and specialized automotive garages, rather than general shops that work on a vast amount of vehicle makes and models.
Due to their high priced nature, most mechanics cannot afford to own individual tools for every type of vehicle that they service, and therefore usually chose a general scan tool that has the capability to upgrade the hardware and software features when needed. Some shops will have several OEM scan tools if they deal primarily with a particular make of vehicles such as an import or GM. Usually they will have a simple code reader for doing fast checks on vehicles with simpler problems.
Tool compliance
Lately vehicle manufacturers have begun implementing a new onboard communication protocol in their electrical systems called CAN (Controller Area Network). The protocol began appearing in the early 2000s, and became a standard on all 2008 and newer. The major benefit of the protocol is the ability for modules to communicate with each other faster due to the higher baud rate. As a result, a CAN compliant scan tool is required for diagnosing the vehicle. Due to the major changes, a majority of non CAN compliant scan tools lack the ability to upgrade to interface with newer CAN vehicles.
Software scanners
AutoTap software display screenshot
An alternative to electronic scan devices, is software that can be purchased or downloaded for free which transforms any notebook, computer, palm pilot, or pocket pc into a code reader or scan tool. The amount of features and support varies greatly based on the application, as some software can only offer minimal features, while others can rival that of an OEM scan tool.
The most inexpensive versions which can be purchased for less than $ 200 or sometimes even found for free, allow any laptop, palm pilot, or pocket pc to be turned into code reader through the use of a diagnostic connector. This allows you to read and clear error codes on any 1996 and newer vehicles with an OBD-2 interface. The more advanced software packages have enhanced codes for specific applications, and support for reading various PIDs such as switch status, voltages, and various sensor outputs.
Basic palm pilots have been phased out for the most part, and can be obtained for less than $ 100. A better option is a pocket pc, with it’s larger and better color display, which usually sells for over $ 400. However, either one can be purchased for a fraction on eBay or craigslist.
In order to use scanner software, an interface cable or wireless module that plugs into the OBD-2 connector is required to permit communication between the device and the vehicle’s computer. Without that, the software is useless. The internet contains numerous sources where an interface cable can be obtained separately, for the enthusiast on a budget. Another possibility is assembling your own interface cable from the various schematics and information available online for free.
Scan tools with scope diagnostics
The Snap-On Solus
Quite a few of the high end professional scan tools have the capability of also functioning as a digital oscilloscope or a graphing multimeter. Certain problems that are usually impossible to diagnose by other means are very easy to detect when the sensor voltages can be displayed as waveforms.
When shopping for a multi-purpose tool with multimeter, scanner, and scope functions, be sure to chose a model that can display multiple waveforms at once. Most professionals can tools can display and simultaneously graph up to four different PIDs.
Hooking up a scope to a circuit or sensor reveals what is happening inside the circuit or device. A scope displays voltage in a time-based waveform. Once you are familiar with reading waveforms, distinguishing bad ones from good ones becomes an easy task. Waveforms can always be compared with scan tool data to see if there are any inconsistencies in the electronic circuits. This is one of the best methods for detecting PCM faults.
Another feature of the scope is the ability to verify and perform action-reaction tests. One channel can be used to monitor the input or action, while the other three channels can be used to monitor the results. An example would be monitoring the crank sensor signal, fuel injector waveform, TPS (Throttle Position Sensor), and ignition pattern when playing with the throttle to spot an intermittent misfire condition.
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It helps to have a working knowledge of scope basics when using a scope, as well as the capabilities of the unit. Just like any other scan tool, various scopes will have different limitations, and therefore doing a little research prior to making a buying decision is recommended.
