I just bought a OBDII scan tool at Harbor Freight on sale for $59. the manual indicates that you should not have the key on when you connect it. Is there ever any reason to have the vechicle running while the scan tool is plugged in? I don't see any info in the manual that forbids it. Though it doesn't say not to, only that the ignition be off before connecting. I don't want to mess this up.

Thanks in advance.

 

The main reason to plug the scan tool in with the key of is to prevent any possible voltage spikes when you plug it in. Voltage spikes are hard on the computer. Many times you will hook up a scan tool and start the engine so that you can see real time data, sensor output and to perform tests if your tool has the software to allow testing.
FYI the 6.0 is a CAN bus compliant computer, the straight OBDII code readers will not work on CAN bus systems. You need a code reader that is CAN bus compliant and specifically designed for FMC expanded codes. You will not hurt anything plugging your OBDII scan tool in, you just will not be able to read any codes if it is not CAN bus & FMC code compliant.

 

Thanks for uor response. The tool is rated as a CAN OBO II code reader. I found it strange however that I could pull the VIN off of My Chev Malibu, but it would not pull the VIN on my 6.0 SD. It does seem to be able to scan other things, but as yet I don't have any tbl. codes for it to read. I wanted to look at the engine while running but didn't want to mess anything up.

 

That is because more than likely the scan tool you purchased is not CAN bus compatible and does not supporte "Enhanced Diagnostic Trouble Codes". The Ford 6.0 SD adopted CAN bus protocol in 2003 with the introduction of the 6.0. Very few manufactures have yet to adopt CAN bus protecol. FMC is the largest auto manufcature to implement CAN bus protocol to date and has the largest database of Enhanced DTC's.

The EPA has mandated that all vehicles sold domestically be CAN-equipped beginning with the 2008 model year. It is projected that about 14% of all vehicles on the road will be CAN-equipped in 2008. Some vendors began using CAN exclusively in the model year of 2004 (Ford, Jaguar, and Mazda). While other manufacturers implemented it selectively in their vehicles beginning in the 2004 model year (Mercedes, Porsche, SAAB, and Toyota).

Enhanced OBD II (EOBD2/EOBDII) Diagnostic Trouble Codes (DTC) are those codes unique to a vehicle of a specific year, make, model (and possibly engine size). Enhanced DTC are assigned by the vehicle manufacturers to cover situations not already covered by a Generic DTC. Enhanced DTC typically begin with 'P1', followed by a 3-digit number (i.e., P1404).

Although Ford Motor Company implements the largest subset of the OBDII standard compared to any other manufacturer, the typical manufactures vehicle only supports 20 - 40 sensors and is limited to emissions power train. Using the enhanced Ford interface, a typical Ford vehicle will support 200 - 300 sensors within half a dozen systems; that's essential systems like ABS, airbags, GEM, etc

It is doubtfull that your Chevy Malibu is CAN bus equipped hence the reason you can see codes on it but not on your 6.0 SD.