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Car Diagnostic Tool suggestions please? I'm looking for a diagnostic system that is compatible with a range of vehicles.  

you might want to look at the OTC 3499N kit..    they can be had for just under 500 bucks...  

this does OBD1 GM / Ford and Chrysler models from the early 80s through 95  and then everything OBD2..   this one on GM cars actually reads live data from the OBD1 system.. where some other consumer models only read codes..
EEC4 fords you run KOEO and KOER tests then clear the codes with this.. you really need on fords to verify with the koeo/koer tests to get the best running engine..      obd1 chrysler this will read live data..  it may also talk to the chrysler transmission controller.. something needed in MOPAR transmission  work in some models..





if you really do a LOT of work on car diagnostics...  you will want a genisys from OTC.. there are a  LOT of options...  and these are NOT cheep.. last time i checked.. the base model was about 1800 bucks.. the price might have changed.. ...




for most car owners... with OBD2 cars...  1996 and newer...  that need to NOT just turn off the check engine light. but actually want to diagnose and repair the systems.. then verify they are fixed.. and this is one i use daily...  this inexpensive unit at 130 bucks actually graphs a lot of the sensor data streams.. so you can verify things like the oxygen sensors are switching voltage at lower engine speeds to verify no air leaks either into the intake or exhaust system..  

the harbor freight 98614...



http://www.harborfreight.com/can-obd-ii-code-reader-eobd-scanner-98614.html

you can easily download the basic instructions from the HF link above.. start reading at section 5.2...

which ever you get .. you will also need factory repair info.. specific to your car..  

a factory service manual in print...   or on CD/dvd..

or .. electronic versions for consumers from alldatadiy  dot com..    or    eautorepair dot net.. this is the most of the same info that professional mechanics have at hand in their work bench computers..  

graphing the oxygen sensor data lets you verify the oxygen sensors are swinging properly...

one does this test at idle...  and looks for the sensor to swing to almost 0.9 volts and down to 0.1 volts repeatedly...

then slowly increase the engine speed to a steady 2500 RPMs...  the pattern will get closer together.. but it will still flip from high to low...

if the idle pattern does not switch .. you might have an air leak.. into the intake manifold..   from the EGR valve .  from the air injection system diverted valves... usually the upstream diverter valve..

being able to see the sensor voltage switching is critical..  

if all the cars you work on are newer than 1996.. start with the HF unit..

if you work on earlier years than 1996..   then you might need one of the OTC models..

there are sometimes a few options available used...  

I have had a look around and the http://www.launchtech.co.uk/creader-vi seems to be a popular choice, has anyone encountered this device and how did you get on?  

Launch C Reader VI Vehicle Coverage

Works with all vehicles compliant with EOBD/OBDII (petrol vehicles from 2001 and diesels from 2004).

Features of the CReader VI include:

MIL Indicator
Ready vehicle information
Readiness status and O2 Sensor detection tests
Read dynamic data stream & freeze frame data
Read / Clear DTC’s


i have seen a lot of inexpensive scan tools that only read the freeze frame data...  this one also does NOT graph the sensor data stream...  

graphing the data stream allows you to see the voltage swings that some of the sensors put out..

this is really important when diagnosing various oxygen sensor codes..  seeing if the oxygen sensor signals are switching from .1 to .9 volts  rapidly when the engine is held at a stable 2500 rpms.. is the usual test... once warmed up.. the oxygen sensors should also be switching high and low at idle..  if they don't .. then you have to look for problems... like vacuum leaks..   egr leaks.. air injection system leaks..   exhaust leaks..     all of those can sent oxygen sensor codes..

see the voltage graph on the display...




one cannot properly diagnose a problem easily with just codes..   once you clear the codes..  they may take weeks to set..  

looking at freeze frame data shows what the system was doing at the instant the code set.. and thats important to look at..   to compare it to the current sensor data .. see what was out of range and what the car was doing when the code set..  

do you have a range of vehicles that you work on..

96 up..???

or 83 to 95 ..

all the mechanics i know.. have multiple scan tools...

if you do 96 newer and want to grab it off line..

try to get a auteltech MS609..   looks like the grey earlier version above.. it does abs and air bag codes also..  

The CReader VI is a pretty good car diagnostic tool and can be used on a wide range of vehicles.