Now here’s a brilliant thingy - a compact device
that plugs into your car’s standard On Board Diagnostics (OBD) port and then
proceeds to log car data up to a maximum of the last 300 hours the car’s been
running. You can log parameters like road speed, rpm, oxygen sensor output and
the airflow meter signal. Then you unplug the device from the car and connect it
to your PC where you can easily graph and analyse the information, including
quickly highlighting high acceleration and braking rates, maximum speeds and so
It’s ideal for someone who wants to check on the
health of engine management sensors. And, as a bonus, the device will also
record fault codes and can then be used to clear them!
The CarChip E/X
The CarChip E/X is only a bit bigger than the OBD
socket itself. So what’s an OBD socket then?
Mandated in the US about 10 years ago, the OBD
port is a standardised diagnostics socket that allows the US authorities to
quickly and easily diagnose engine management maladies that could cause the car
to no longer be emissions legal. With the legislated requirement that the socket
be fitted and that a standardised protocol be used (actually, a number of
protocols are permitted), car manufacturers also adopted the system for their
own diagnostics. However, the manufacturer-specific data is in addition to the
OBD data. In other words, all cars sold in the US have an OBD socket with
certain standardised information available from it, while manufacturer-specific
diagnostics tools can access further information that pertains to just that
The CarChip E/X makes use of the universal OBD
data – vehicle speed, engine speed, throttle position, coolant temp, engine
load, intake manifold pressure, airflow rate, intake air temp, ignition timing
advance, fuel pressure, short-term fuel trim, long term fuel trim, oxygen sensor
voltage, battery voltage and fuel system status. Note that many cars will not
support all of these parameters (for example, a car with a MAP sensor will not
support airflow rate) so this is the maximum possible list of parameters able to
be generically read from the OBD port. At any one time, a maximum of four
parameters is able to be logged by the CarChip E/X.
Configuring the CarChip E/X
After the software is loaded on the PC, the
CarChip E/X is connected via a dedicated USB adaptor cable. A ‘Walkthrough
Setup’ procedure is then initiated that allows the user to select metric or
imperial units, the name of the vehicle and driver, the CarChip serial number
and whether the data is automatically cleared from the CarChip when it is
downloaded to the PC. Under the ‘Choose Other Parameters’ tab you can set what
parameters you want logged. These can be set to be logged at 5, 10, 20, 30 or 60
Thresholds can also be set for what is defined by
the data analysis as hard braking, extreme braking, hard acceleration, extreme
acceleration and various speed bands. The braking and acceleration levels are
presumably determined by the change of speed over time.
The software is largely self-explanatory and is
quite easy to use.
Installation of the CarChip E/X in the car takes
only a few seconds.
Step 1 is to locate the OBD socket. By regulation
this must be positioned near the steering wheel and it’s also required that it
be accessible without tools. Common positions include under the steering column,
under a trim panel in the centre console or up under the dash.
Step 2 is to plug the CarChip E/X into the OBD
Step 3 is to start the car and make sure the data
logger indicator LED on the device is flashing. (If this LED is distracting, it
can be configured ‘off’ in the software.)
And that’s it for installation!
Analysing the Data
The CarChip E/X stores data for up to 300 hours of
driving and then starts over-writing the oldest data. However, at any point you
can remove the device from the car and download the data to your PC that then
displays it in the form of separate trips.
For each trip you can display the logged
parameters in graphical or tabular forms. In addition to the logged parameter,
each graph also shows where acceleration and braking thresholds have been
exceeded. A ‘report’ can be brought up that shows data including the start and
stop times of the trip, amount of time spent in each speed band, distance,
average and maximum speeds and hard braking and acceleration events.
The graphs of sensor outputs can be used to assess
the health of the sensor. For example, oxygen sensors in most cars should show a
swing from about 0-1V. A dead oxygen sensor will not only have a low voltage
output but quick changes will also be absent.
However, for diagnostics, the first step should be
to view the Vehicle Trouble Log. This displays any logged fault codes and
significantly, also shows a snapshot of engine parameters at the time the fault
code was logged. These parameters include intake manifold pressure, coolant
temperature, calculated load value, engine speed, vehicle speed, shot and
long-term fuel trims, and whether the engine management system is working in
open or closed loop operation. Note that these snapshot parameters are not
dependent on the parameters you have chosen to log long-term.
But it’s important to realise that the logged
trouble codes may be manufacturer-specific. The software gives a guide as to
what each trouble code may mean but these are quite likely to be wrong – best
that you Google the trouble code (eg “Honda Insight P1447”) rather than relying
on the suggestion. The software can also be configured to delete the trouble
code, but again this may not be successful if the trouble code is
The software also includes the ability to replay
the vehicle speed for the 18 seconds prior to a sudden stop. The software calls
this an ‘Accident Log’ and it may be useful where the vehicle is involved in an
accident. However, we think such information would easily be able to be
challenged in a court of law.
screen grab shows the speed log of one trip. The timings on the horizontal axis
show the trip started at 1:55pm on July 29 and finished at 2:13pm. The vertical
red trace (arrowed) indicates a hard braking event. The threshold for this (and
extreme braking, hard acceleration and extreme acceleration) can all be
output of one of the oxygen sensors, logged over the same trip. This shows that
(a) the oxygen sensor is in good health (the output rapidly varies a great deal)
and that (b) the car ran fairly lean mixtures for much of the time (output
voltage mostly below 0.5V). Logging of the short and long-term fuel trims would
indicate if these mixtures were leaner than desirable – if they were (say
because of a blocked fuel filter), the fuel trims would show major change.
is the report for the same trip. At a glance, it can be seen that there was one
hard braking event, no hard acceleration, most of the time was spent at less
than 72 km/h (in fact, the average speed was 61 km/h) and the maximum speed was
report shows a logged trouble code. In addition to the trouble code number being
cited (P1447), the report also shows the engine parameters at the time the code
was logged. This information makes tracing intermittent faults much easier.
The CarChip E/X costs AUD$286. A cheaper version
(the CarChip) with a shorter 75 hour logging capability is available at
For your money you get an effective and small data
logger that can remain plugged into the car semi-permanently. It will clearly
show how the car is being driven on each trip, reads fault codes and is able to
clear some of them. Furthermore, if you need to monitor sensor outputs (useful
if the car is being modified) then the CarChip will do that as well.
Contact: Ecowatch 03 97617040 www.davisinstruments.com.au
Will It Fit My Car?
first step in ascertaining whether the CarChip will work with your car is to see
if it has an OBD port. However, that is not the end of the matter. Many
cars sold in Australia were produced with an OBD port but the internal ECU
software to output OBD data was not enabled. (For example, Toyota and Lexus
models of around 1998 - 1990 have an OBD port but OBD readers will not work with
produced after about 1991 that have an OBD port and which were also sold in
the US are highly likely to have OBD capability. Australian-built cars with
an OBD port may or may not have OBD capability; again, the more recent the car,
the more likely an OBD reader will work.
CarChip works with the following OBD protocols: J1850-41.6, J1850-10.4, ISO9141,
KWP2000 and CAN.