Rick's Free Auto Repair Advice

Which scan tool to buy

Which scan tool to buy

You can diagnose and fix your own car, but only if you have the right tools. Don’t know which scan tool to buy? I’ll help you figure it out so you can stop relying on the auto parts store to scan your vehicle. Auto parts stores use basic code readers and the clerks will tell you to replace whatever part is listed in the trouble code. You need real diagnostic data to find out if the sensor is really bad or actually telling the truth, which means you’ve got an underlying engine air/fuel problem. The only way to get that diagnostic information is from a scan tool that shows LIVE DATA and is bi-directional. In the past, those scan tools cost several thousand dollars. But now you can get live data for less than $100.

In the old days you needed a tach/dwell meter and a timing light to do any work on your own car. Well, today you need a scan tool. Quiturbitchin and buy one. It’ll save you money right away and really help you nail down the root cause of your problems.

Here’s how to know which scan tool to buy:

1) Code reading capabilities – Most scan tools read generic Powertrain “P” codes. Fine, but you want a scan tool that also reads manufacturer-specific P codes.

Next, you want a scan tool that also reads Body “B” and Chassis “C” codes. Those codes relate to airbags, ABS brakes, and body control modules. Just as an FYI, body control modules issues are a huge headache these days. If your scan tool can’t read them, you’ll be lost when trying to diagnose simple issues like lights that don’t work or wiper problems.

2) On-board code definitions – All code readers and scan tools can pull up the trouble code. But the better units also include the definition so you don’t have to go look it up. In addition, the best units also give you the most likely cause of the code. Nice feature to have!

3) Live data – There’s live data, and then there’s lots of live data. Some scan tools can only display a few parameters. You want a tool that can display as much as possible. At the very least you want to know short and long term fuel trim values, MAF, MAP, O2, ECT, TPS, RPM readings.

4) Bi-directional Car makers have actually made car diagnostics easier by allowing you to actuate certain items right from the scan tool. Here’s an example; your car is overheating and you want to know if the radiator fans are working. You could hot wire them, but many radiator fans are multiple speed or variable speed. If you hotwire, you may trick yourself into thinking the fan is working. But if you have a scan tool with bi-directional capabilities, you can command the speed you want right from the scan tool. That confirms or eliminates a fan problem without lifting a finger.

5) Mode $06 – Trouble codes set when a fault exceeds the programmed value determined by the manufacturer. But what if you have a misfire that hasn’t set a trouble code? Well, with a Mode $06 capable scan tool, you can dig deep into the vehicle’s computer to see exactly which cylinder has misfired, how many times it’s misfired, and what the threashold is for setting a trouble code. If you see that cylinder #6 has misfired 200 times but the threshold is 500, and no other cylinders show a misfire, well it’s a pretty good bet that cylinder #6 has a problem.

6) U codes – Most new cars transmit digital data across at least one data bus. The headlight switch, for example, calls for headlight operation. The switch is connected to the body control module. The body control module may send a digital command to the front control module (in a Chrysler application) and it’s the front control module that actually provides power to the headlights. If there’s a problem anywhere along the data bus, it’ll show up as a “U” code. This is a really nice feature to have, but it really boosts the price of the scan tool.

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat

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