If anything the powertrain control system can detect becomes an issue, the ECM/TCM/PCM will log a diagnostic trouble code (DTC). This code can point you in the right direction if you or your mechanic is looking to fix the problem. However, the code isn’t a full diagnosis. There are various possible causes behind each code. Here’s a list of tools that can help you diagnose diagnostic trouble codes yourself:
OBD Code Readers & Scan Tools
Let’s start with OBD code readers and scan tools. These car diagnostic tools retrieve data from your vehicle’s PCM. They then relay this data as diagnostic car trouble codes for you to look through. Code readers are generally more bare-bones than professional scan tools. While scan tools will give you data readouts and troubleshooting tips, code readers are still a good pickup if you’re just starting out. They’ll tell you the codes plain and simple, and those codes will be a good starting point for the rest of your diagnosis.
The Performance Tool OBDII Digital Diagnostic Scan Tool is a great buy for any budding DIYer in need of a simple and effective code reader. Here are some scan tools you can find at CarParts.com:
More affordable scan tools are read-only. More expensive scan tools can issue commands to the PCM to turn on the cooling fan or kill separate injectors when you’re chasing a misfire. Also, the more expensive units can program keys and reset TPMS sensors. If you just want to pull a code and get an idea of why the MIL is illuminated, an inexpensive code reader might be better.
There are also dongles you can buy that will interface with your smartphone via an app (see photo). Even some of the more inexpensive dongles have tremendous capabilities and the ELM 327 will even interface with your Android radio if you install the app. Dongles like the BlueDriver are more powerful and professional grade.
Other Testers
As we’ve mentioned, the OBD code only points you in the direction of the problem. If you want to thoroughly diagnose your vehicle’s systems, there are a few other testers you might want to pick up.
Multimeters
If the OBD codes that your vehicle is triggering are related to its electrical system, pick up a multimeter. Multimeters are invaluable tools for testing your vehicle’s electrical system. They measure current, resistance, and voltage, and more expensive multimeters can measure temperature and frequency.
You can even test your car’s battery with a multimeter. The same goes for your vehicle’s headlight bulbs, fuses, and alternator.
The OTC Multimeter (shown on the right in the photo) includes various contact tips and different wires to suit different needs. Its sleek design has accents of yellow and blue on its labels, and it comes with a 24-month warranty.
The Performance Tool Universal Multimeter (shown on the left in the photo) is simple and no-nonsense. It has white labels on a black body and comes with a set of wires. As a compact tool, it’ll surely serve you well as you hunt down what’s causing those electrical trouble codes.
Circuit Testers
A car circuit tester is another tool you can use to test your vehicle’s electrical lines and identify what’s triggering certain diagnostic trouble codes. It’s a portable electrical circuit shaped like a screwdriver with a wire running out its bottom attached to a metal clamp.
While you can’t use a circuit tester to retrieve data like fuel trim (that’s only available using scan data), you can use a circuit tester with a low impedance bulb (pulls about .25 amps) to check for power at components like injectors or solenoids.
A low impedance circuit tester is better than a multimeter or scan tool for checking power. The multimeter can show voltage and measure resistance, but can’t tell you if there is enough current being delivered to carry the necessary electrical load.
To use a circuit tester, attach the clamp to ground and tap the probe tip to the electrical circuit’s source. If the bulb in the handle lights, it means electricity is flowing between those components.
Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.
Pro Tip: If you’ve disconnected a component and you’re checking the terminals in the connector, do not shove the tip of the probe into the terminal or you’ll destroy it. Inexperienced DIY folks have a tendency to do this.
Logic probes will have both a positive and a negative connection and an LED that lights up green for ground and red for B+. This is handy for checking reversible motor circuits like power windows.
Keep in mind: circuit testers are great for testing wiring connectors and other automotive electronics. They’re not suitable for measuring sensor voltages but are good for routine electrical troubleshooting on anything that isn’t a computer input. To begin with, you won’t know how much voltage is present using a logic probe or circuit tester, only that voltage is present, and that’s not good enough when you’re chasing most trouble codes.
The OEMTOOLS One-Handed Wire Piercing Circuit Tester helps you troubleshoot primary circuits in difficult areas around your vehicle. It has a 12-foot heat- and oil-resistant coiled cord and a hook-like tip to hang on wires.
For relay circuits, you can buy the OEMTOOLS Relay Circuit Tester. It has a different design from the typical circuit tester and has large metal clamps instead of a single small clamp and metal tip. This circuit tester also includes different relay leads.
The OEMTOOLS Heavy-Duty Circuit Tester is a simple tool made with quality materials. It has a stainless steel probe with a heavy-duty cord and an insulated ground clip. In addition, this circuit tester has a high-intensity LED bulb in its handle for easier visibility.
Cooling System Pressure Testers
If your vehicle recently had a cooling system flush, you need to make sure the cooling system pressure is at the correct psi. Otherwise, the system might fail to cool your engine, and you’ll face a ton of different trouble codes. The cooling system pressure tester attaches to the radiator, where you can pump it by hand to match the pressure level written on the radiator cap. After leaving the tester there for 20 to 30 minutes, see if the pressure reading on the tester is lower than before. If it is, look for a leak. You can also use the cooling system pressure tester to test the radiator cap if it has a radiator cap attachment.
The Motorad Cooling System Pressure Tester is a handy tool that comes in its own black case. This keeps all its important fittings together.
The OEMTOOLS Cooling System Pressure Test Pump is another option if you want a simple tool to check your cooling system’s pressure levels. It can work with most cooling system adapters and has a lever-style pressure relief valve for easy release.
Ignition Spark Testers
If your code reader is picking up ignition-related diagnostic trouble codes, you might want to invest in a car ignition spark tester. Ignition coils take the low electrical voltage from the battery and transform it into high voltage to the spark plugs. Your code reader can point you to the specific engine cylinder experiencing issues. From there, disassemble and retrieve the ignition coil and plug the tester in. Follow the tester’s instructions after that. Once you start the engine up with the ignition spark tester attached, it will spark if the ignition coil is in full working order. If it doesn’t spark, you’ve likely found the cause behind your ignition-related DTC.
The OEMTOOLS Adjustable Ignition Spark Tester is a particularly versatile tool that works with large and small engines. It can simulate spark plugs under compression load to adequately test their spark length.
Meanwhile, the OEMTOOLS Inline Ignition Spark Tester is a hands-free tester with a clear plastic body sturdy enough to withstand rough use.
And there you have it! You likely don’t need all these tools in your automotive arsenal, but they’re great to have on hand when you’re itching to find those troublesome DTC triggers.
Keep Reading: Related Posts
Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.
